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Abstracts

SERIES Concluding Workshop -

Joint with US-NEES

“Earthquake Engineering Research

Infrastructures”

JRC-Ispra, May 28-30, 2013

In memory of Prof. Roy Severn

SERIES Concluding WS – Joint with US-NEES: Abstracts

i

Contents

Session 1: Hybrid Testing

Towards faster computations and accurate execution of real-time hybrid simulation

Mosalam KM, Günay S 2

Robust integrated actuator control strategy for real time hybrid simulation

Ou G, Dyke SJ, Wu B 3

Real-time earthquake simulationusing force controlled actuators

Nakata N, Krug E 4

Numerical tools for the reduction of complex dynamic models

Abbiati G, Bursi OS, Cazzador E, Mei Z 5

A support platform for distributed hybrid testing

Lamata Martinez I, Obón Santacana F, Williams MS, Blakeborough A, Dorka UE 6

Monolithic time-integration algorithms for Hamiltonian systems suitable for real-time hybrid simulations

Abbiati G, Bonelli A, Bursi OS, Reza MS 7

Pseudo-dynamic testing with non-linear substructuring of a reinforced concrete bridge based on system

identification and model updating techniques

Abbiati G, Bursi OS, Cazzador E, Mei Z, Paolacci F, Pegon P 8

Assessment of the seismic behaviour of a retrofitted old RC highway bridge through PsD testing

Bursi OS, Ceravolo R, Di Sarno L, Erdik M, Paolacci F, Sartori M, Pegon P 9

Pseudo-dynamic testing of a piping system based on model reduction techniques

Reza MS, Abbiati G, Bonelli A, Bursi OS 10

Advanced Hybrid Simulation Frameworks for Civil Structures

Phillips BM, Spencer BF Jr. 11

Geographically distributed continuous hybrid simulation tests using shaking tables

Obón Santacana F, Dorka UE 12

Dynamic substructuring for soil structure interaction using a shaking table

Tang Z, Dietz M, Li Z, Taylor C 13

Real-time hybrid testing for soil-structure interaction: An adaptive signal processing framework

Dertimanis VK, Mouzakis HP, Psycharis IN 14

Towards an implementation of the FHT technique for SSI systems using nonlinear macroelements

Chatzigogos CT, Dietz M, Pecker A, Tang Z 15

Session 2: SERIES Transnational Access to Centrifuge Facilities

Centrifuge modeling of dynamic behavior of box-shaped underground structures in sand

Ülgen D, Sağlam S, Özkan MY, Chazelas J-L 17

Investigation of the seismic behaviour of shallow rectangular underground structures in soft soils using

centrifuge experiments

Tsinidis G, Rovithis E, Pitilakis K, Chazelas J-L 18

Investigation of several aspects affecting the seismic behaviour of shallow rectangular underground structures

in soft soils

Tsinidis G, Heron C, Madabhushi SPG, Pitilakis K, Stringer M 19

Experimental verification of shallow foundation performance under earthquake-induced liquefaction

Karamitros DK, Cilingir U, Bouckovalas GD, Madabhushi SPG, Papadimitriou AG, Haigh SK 20

Centrifuge modelling of the performance of liquefaction mitigation measures for shallow foundations

Marques A, Coelho P, Haigh SK, Madabhushi SPG 21

Centrifuge modeling of pairs of flexible retaining walls in saturated sand under seismic actions

Aversa S, De Sanctis L, Maiorano RMS, Tricarico M, Viggiani G, Conti R, Madabhushi SPG, Stringer M, Heron C

22

Experimental and numerical investigations of nonlinearity in soils using advanced laboratory-scaled models: An

application to the Rome historical centre

Bozzano F, Bretschneider A, Giacomi AC, Martino S, Scarascia Mugnozza G, Escoffier S, Lenti L, Chazelas J-L, Favraud C, Macé D 23


ii

Session 3: US-NEES developments

The George E. Brown, Jr., Network for Earthquake Engineering Simulation (NEES): Accelerating improvements

in seismic design and performance by serving as a global collaboratory for discovery and innovation

Ramirez J 25

Promoting re-use of Earthquake Engineering data through the NEEShub

Browning J 26

Re-use of experimental earthquake data for research: Three illustrative examples

Van de Lindt JW 27

Communicating earthquake engineering:The education, outreach, and training activities of the George E.

Brown, Jr. Network for Earthquake Engineering Simulations

Fossum B 28

Damping estimation from seismic records

Bernal D 29

Session 4: SERIES Networking Activities: Distributed Database and Qualification of Research

Infrastructures

A faceted lightweight ontology for earthquake engineering research projects and experiments

Hasan MR, Farazi F, Bursi OS, Reza MS 31

The SERIES Distributed Database: Architecture and implementation

Lamata Martinez I, Ioannidis I, Fidas C, Williams M, Pegon P 32

The SERIES Distributed Database: Exchange format, local DBs and central portal interface

Bosi A, Bousias S, Chazelas J-L, Dietz M, Hasan MR, Madabhusi SPG, Prota A, Blakeborough T, Pegon P

33

Qualification of seismic research testing facilities in Europe

Zola M, Taucer F 34

Session 5: SERIES Transnational Access to Shaking Table Facilities on masonry, RC and steel

structures

Full scale testing of modern unreinforced thermal insulation clay block masonry houses

Lu S, Jäger A, Mendes L, Candeias P, Campos Costa A, Coelho E, Degée H, Mordant C, Sendova V,

Rakicevic ZT, Tomazevic M 36

Assessment of innovative solutions for non-load bearing masonry enclosures

Leite J, Lourenço PB, Vintzileou E, Palieraki V, Correia AA, Candeias P, Campos Costa A, Coelho E 37

Seismic behaviour of L- and T-shaped unreinforced masonry shear walls

Mordant C, Dietz M, Vasseur L, Degée H 38

Shake table testing of a half scaled RC-URM walls structure

Tondelli M, Petry S, Lanese I, Beyer K, Peloso S 39

Experimental and numerical investigation of torsionally irregular RC shear wall buildings with Rutherma

breakers

Yakut A, Le Maoult A, Richard B, Ragueneau F, Atanasiu GM, Scheer S, Diler S 40

Assessment of the seismic response of concentrically-braced steel frames

Broderick BM, Hunt A, Mongabure P, LeMaoult A, Goggins JM, Salawdeh S, O’Reilly G, Beg D, Moze P, Sinur F,

Elghazouli AY, Plumier A 41

Session 6: SERIES Transnational Access to Shaking Table Facilities on wood structures / General on

Experimental facilities

Seismic performance of laminated wood frames with moment connections under seismic loads:Experimental

investigation

Kasal B, Heiduschke A, Pospisil S, Urushadze S, Zembaty Z 43

Investigation of seismic performance of multi-storey timber buildings

Piazza M, Tomasi R, Campos Costa A, Candeias P 44


iii

Experimental study on seismic performances of precast concrete shear wall with joint connecting beam

Lu X, Wang D, Zhao B 45

Full-scale pseudodynamic testing of the SAFECAST three-storey precast concrete building

Bournas D, Negro P, Molina F-J 46

Experimental earthquake engineering research in LNEC: Contribution to global seismic performance assessment of structures

Coelho E, Campos Costa A, Candeias P, Mendes L, Correia A 47

Session 7: Analytical and Experimental work on soil structure interaction, wave propagation and

field testing, including SERIES Transnational Access to Shaking Table Facilities

Large-scale Laboratory Experiments of landslide generated Tsunamis in the NEES Tsunami wave basin half a

century after the Vajont Dam disaster

Fritz H, McFall BC, Mohammed F 49

Caisson foundations subjected to seismic faulting: Reduced-scale physical modelling

Anastasopoulos I, Zarzouras O, Georgarakos T, Drossos V, Gazetas G 50

Effect of soil structure interaction on higher modes participation

Mirfattah SA, Mirfattah SK 51

Estimation of soil structure interaction effects, considering the frequency content of the motion

Mirfattah SH, Mirfattah SA 52

Development of new infinite element for numerical simulation of wave propagation in soil media

Sesov V, Edip K, Cvetanovska J 53

Design and construction of laminar container for 1-g shaking table tests

Sesov V, Cvetanovska J, Edip K, Rakicevic ZT 54

Analysis of the dynamic behavior of squat silos containing grain-like material subjected to shaking table tests

Foti D, Ivorra S, Trombetti T, Silvestri S, Gasparini G 55

Study of multi-building interactions and site-city effect through an idealized experimental model

Schwan L, Boutin C, Dietz M, Padron LA, Bard PY, Castellaro S, Ibraim E, Maeso O, Aznárez JJ, Taylor C

56

EuroProteas: A full-scale experimental facility for soil-foundation-structure interaction studies

Pitilakis D, Rovithis E, Anastasiadis A, Pitilakis K 57

Session 8: Analytical and Experimental Techniques / SERIES Transnational Access to Reaction Wall

Facility

In-situ seismic performance tests of a scoured bridge

Chang K-C 59

Validation of a visual deformation measurement system

Binbir E, Demir C, Ispir M, Ilki A 60

Development of wireless sensors for shake table and full scale testing and health monitoring of structures

Rakicevic ZT, Markovski I, Filipovski D, Micajkov S, Garevski M 61

Recent advances in seismic design of RC tall buildings using ultra-high-strength materials in Taiwan

Hwang S-J 62

Refined and simplified numerical models of an isolated old highway bridge for PsD tests

Paolacci F, Alessandri S, Mohamad A, Corritore D, Derisi R 63

Full-scale experimental validation of dual eccentrically braced frame with removable links

Stratan A, Dubina D, Ioan A, Taucer F, Poljansek M 64

Session 1 – Hybrid Testing

1

Hybrid Testing

Session 1

Tuesday, 28 May 2013


2

TOWARDS FASTER COMPUTATIONS AND ACCURATE EXECUTION OF

REAL-TIME HYBRID SIMULATION

Khalid M. Mosalam and Selim Günay

University of California, Berkeley, USA

This paper reports three recent developments aimed towards faster computations and more

accurate execution of real-time hybrid simulations (RTHS). These developments were

conducted at the University of California, Berkeley as part of nees@berkeley site

development for an NSF-funded early–concept grant for exploratory research (EAGER)

project, namely “Next Generation Hybrid Simulation – Evaluation and Theory”.

The first of these developments is a standalone RTHS system which can accommodate

integration time steps as small as 1 milisecond. This fast execution time of an integration time

step is realized by a combination of the computation power introduced by a digital signal

processor (DSP) card, the physical data transfer between the computational platform and the

controller and the real-time compatible PID control technology of the controller and the

servo-hydraulic system. The fast execution feature eliminates errors that would be introduced

by the application of a predictor-corrector smoothing technique. Applications of the

developed RTHS system in testing porcelain and polymer composite insulator posts for high

voltage electrical switches are presented and discussed.

The second development is the use of an efficient equation solver in RTHS which decreases

computation time. This efficient solver, which decreases the computation time by factorizing

the Jacobian of the system of linear algebraic equations only once in the beginning of the

simulation, is especially beneficial in RTHS which involves analytical substructures with

large number of degrees of freedom. Applications of this development for multi-story multi-

bay framed structures with both linear and nonlinear constitutive relationships are presented.

The third development is a novel use of a three-variable control (TVC) for RTHS on a

shaking table configuration. Although the TVC, which employs velocity and acceleration

control in addition to the usual displacement control, is nowadays used in conventional

shaking table tests, this development is one of the very first applications of TVC in RTHS. It

is demonstrated that the TVC enhances the acceleration tracking in high frequencies, while

still eliminating the time delay between the command and feedback displacement signals.

Accordingly, adopting the TVC enhances the performance and reduces the errors in RTHS.


3

ROBUST INTEGRATED ACTUATOR CONTROL STRATEGY

FOR REAL TIME HYBRID SIMULATION

G. Ou1, S. J. Dyke

1, B. Wu

2

1 Purdue University, USA

2 Harbin Institute of Technology, P.R. China

Real time hybrid simulation (RTHS) is able to perform substructure test in real time scale and

includes rate dependent feature in consideration. One major challenge for RTHS is that it

requires accurate and prompt execution of boundary condition that is calculated from

numerical substructure. In most cases, traditional PID control induces large time lag between

desired command and response which may cause system instability and further the failure of

the test. Many control strategies for servo hydraulic actuator-structure system have been

proposed recently to compensate such time lag and other system dynamics. This paper

introduces a new integrated control strategy into RTHS.

The new proposed Robust Integrated Actuator Control (RIAC) algorithm integrates three key

control components; first is the loop shaping feedback control based on H-∞ optimization,

second one is a pure delay feed-forward block for control performance enhancement and an

additional Kalman filter for feedback estimation and noise reduction. The combination of the

aforementioned blocks provides flexible performance based controller design according to

different evaluation criterion.

RIAC has been tested for displacement tracking on different actuator setups and proved to

work effectively. The efficacy of the proposed strategy is demonstrated through RTHS of a

3DOF steel structure with equipped magnetorheological (MR) damper. The experimental

components herein is the MR damper attached to a large scale actuator has maximum force

capacity of 2500KN, the numerical substructure is the rest of the steel structure.


4

REAL-TIME EARTHQUAKE SIMULATION

USING FORCE CONTROLLED ACTUATORS

Narutoshi Nakata, Erin Krug

Johns Hopkins University, USA

This paper reports experimental real-time earthquake simulations using force controlled

hydraulic actuators. The method presented here is often referred to as effective force test

(EFT) method. An experimental setup consisting of a two-degrees-of freedom structure and

two hydraulic actuators at the Johns Hopkins University is utilized for implementation,

verification and validation of multidegrees-of-freedom EFT. Force feedback controller design

and experimental results are presented and performance and limitations of EFT are discussed.

The idea of the EFT method is to impose a loading to structures that is equivalent to a

reference ground motion using force-controlled hydraulic actuators.

Experimental results in harmonic simulation tests proved that the centralized decoupling loop

shaping force feedback controller was able to independently control forces in the two

actuators without interaction. Experimental results in earthquake simulation tests showed that

the dynamic forces were accurately controlled to provide tracking while maintaining

robustness. In summary, this paper experimentally proves that MDOF-EFT is feasible with a

centralized decoupling loop shaping force feedback controller.


5

NUMERICAL TOOLS FOR THE REDUCTION OF

COMPLEX DYNAMIC MODELS

G. Abbiati1, O.S. Bursi

1, E. Cazzador

1, Z. Mei

1,2

1University of Trento, Italy

2Harbin Institute of Technology, China

Over the last decade, Real-Time (RT) and Pseudo-Dynamic (PsD) testing with Dynamic

Substructuring (DS) have gained significant popularity due to their versatility in testing

several types of linear and nonlinear structural systems. Nonetheless, despite the continuous

increase of computing power, implementation issues relevant to the typical solution time of

the Numerical Substructure (NS) make complex Finite Element (FE) models not suitable for

testing purposes. Moreover, time integration algorithms characterized by a deterministic

convergence time are crucial for real-time machines, whereby hybrid simulation code is

executed. As a consequence, optimal NSs capable of reproducing the behaviour of complex

dynamic linear/nonlinear systems must be tailored to ensure robustness to hybrid simulation.

In this perspective, a set of numerical tools devoted to the reduction of parts of NS models is

presented. With regard to the linear case, MatLAB implementations of well-known reduction

methods such as Guyan, System Equivalent Reduction-Expansion Process (SEREP), and

Craig-Bampton are provided. With respect to the nonlinear case, state space models can

finely synthetize complex systems. Nonetheless, the identification of the parameters of such

models is a quite non-trivial task. When the trial and error strategy fails, an optimization-

based approach must be adopted. The tool we are proposing herein sets the optimum problem

in the time-frequency domain. In particular, the minimization of a certain penalty function

forces the Short Time Fourier Transform (STFT) of the response of a simplified state space

model to match the STFT of the response of the reference model being reduced. The model

reduction of piers belonging to the fiber-based FE model of an old reinforce concrete viaduct

is presented as an application example. In particular, in order to simulate the typical

hysteretic behaviour of each single pier, the 3-DoFs linear model obtained from the dynamic

substructuring is combined with a Bouc-Wen spring in series with a slip-lock element. The

optimal tuning of the resulting state space model is done by means of the proposed tool and

comparisons are performed with the reference fiber-based FE model.


6

A SUPPORT PLATFORM FOR DISTRIBUTED HYBRID TESTING

Ignacio Lamata Martinez1, Ferran Obon Santacana

2, Martin S. Williams

1,

Anthony Blakeborough1, Uwe E. Dorka

2

1 University of Oxford, Department of Engineering Science 2 University of Kassel, Institute of Structural Engineering

Large-scale testing continues to play an important role in earthquake engineering, generating

research results that lead to improved safety and security of European society. Distributed

hybrid testing offers a promising approach to use resources from geographically separate

laboratories in a highly efficient way, to perform more complex, larger-scale tests than are

possible in most individual laboratories. The method involves splitting a structure into a set

of substructures (some tested physically, some modelled numerically) located in different

laboratories. Simulation of the full structural response involves simultaneous testing of the

substructures with feedback of data between them, requiring fast communication through

computer networks. To handle systems involving rate dependence, there is a desire for test

speed to approach real time.

Organizing and planning distributed experiments entails much more complexity than is

involved in a single-laboratory hybrid test, besides the difficulty of tracing errors caused by

the distributed environment. This points to the importance of a platform to support the testing

activities.

This platform has been achieved by means of a specification called Celestina, created at the

University of Oxford. Celestina provides a framework for conducting the experiment

workflow. It provides a specification for the services to be implemented, under three main

headings of networking, test definition and experiment execution, and supports the actual

data exchange during a test. It does not force any particular implementation, which can be

independently developed and implemented under this framework, and nor does it restrict the

actual method of data exchange.

In this article we discuss the design and conception of the specification as well as one

implementation that has been validated through a series of substructured “numerical

experiments” in partnership with the University of Kassel. In a typical substructured test,

nodes at Oxford and Kassell were used to simulate the response of a 33-DOF steel frame

fitted with a TMD, with both nodes conducting testing (in simulation) according to

instructions from a Celestina-based program running in Oxford.


7

MONOLITHIC TIME-INTEGRATION ALGORITHMS FOR HAMILTONIAN

SYSTEMS SUITABLE FOR REAL-TIME HYBRID SIMULATIONS

G. Abbiati, A. Bonelli, O.S. Bursi, Md S. Reza

University of Trento, Italy

In recent years, hybrid simulation techniques like Real-Time (RT) and Pseudo-Dynamic

(PsD) testing with Dynamic Substructuring (DS) became more and more popular to study in

depth the performance of structures subject to dynamic loads. With regard to relevant time-

stepping methods, they can be broadly classified into monolithic and partitioned. According

to the RTDS philosophy, in the monolithic approach, just the Numerical Substructure (NS) is

integrated whilst the remainder part, i.e. the Physical Substructure (PS), is considered as a

black box. Since common differential models aimed at simulate nonlinearities in the NS

make use of state space formulations based on extended state vectors, e.g. the Bouc-Wen

model, time integration algorithms conceived for Hamiltonian systems are preferable. In this

perspective, we provide the Simulink implementations of two time integration algorithms

belonging to the monolithic class and tailored to first order systems: i) the linearly implicit

Rosenbrock-based L-Stable Real-Time compatible (LSRT) algorithm with two stages; ii) the

Modified Generalized- (MG- ) method. For a proper selection of the parameters both the

algorithms are characterized by second order accuracy and linear stability. In particular, the

MG- allows for user controlled algorithmic damping. In order to validate the

implementations, RTDS experiments on a full-scale industrial piping system are presented.


8

PSEUDO-DYNAMIC TESTING WITH NON-LINEAR SUBSTRUCTURING OF A

REINFORCED CONCRETE BRIDGE BASED ON SYSTEM IDENTIFICATION

AND MODEL UPDATING TECHNIQUES

G. Abbiati1, O.S. Bursi

1, E. Cazzador

1, Z. Mei

1,2, F. Paolacci

3 & P. Pegon

4

1University of Trento, Italy;

2Harbin Institute of Technology, China

3University of Roma Tre, Italy;

4Joint Research Centre, Italy

The seismic performance assessment and retrofit of a concrete bridge by means of a testing

program was conceived within the RETRO research activity funded by the SERIES project.

The old 400m span Rio Torto viaduct, under-designed with respect to the seismic load, is

considered as Case Study. The installation of a couple of isolation devices -one per column-

for each pier portal frame interposed between the cap beam and the deck was proposed to

achieve the Eurocode 8 seismic-performance requirements. A software framework devoted to

test the effectiveness of the seismic retrofit of the bridge through a set of hybrid simulations

is presented. In particular, two of the twelve piers - Physical Substructures (PSs) - will be

loaded through dynamic actuators, whilst the remaining ten piers and the deck as well -

Numerical Substructures (NSs) - are numerically modelled and solved. A refined Finite

Element (FE) fiber model of the bridge is implemented in the well-known OpenSEES

software to support the pseudo-dynamic test design. Time history analyses conducted on the

reference model highlighted appreciable nonlinearities of the pier dynamic responses already

under the Serviceability Limit State. As a consequence, a NS capable of reproducing this

nonlinear behaviour during hybrid simulations is deemed necessary. Nonetheless,

implementation issues relevant to the typical execution time of the NS - few milliseconds or

controller time steps - make complex FE fiber models unsuitable for testing purposes. A

rigorous nonlinear dynamic reduction of numerical piers was conceived as an extension of

the Craig-Bampton method; thus, the 3-DoFs model resulting from the linear dynamic

substructuring of each single pier is endowed with a simplified Bouc-Wen spring in series

with a slip spring. Since moment resisting reinforced concrete piers develop a ductile

response by activating different yielding mechanisms at different excitation levels, a test

procedure aimed at propagating damage from physical to numerical piers is devised: in order

to match the dynamic response of the reference OpenSEES model, at each run, a priori

unknown nonlinear parameters characterising the 3-DoFs reduced piers will be tuned by

means of a robust time-frequency approach. The constitutive laws of fiber-based beam

elements of the reference model will be updated from experimental measurements obtained

during the previous test. Lastly, the selected continuous time testing strategy together with a

complex NS forced the adoption of a time integrator which allows for subcycling; for this

purpose, the parallel partitioned PM algorithm is proposed and its experimental

implementation to the Rio Torto case study is presented.


9

ASSESSMENT OF THE SEISMIC BEHAVIOUR OF A RETROFITTED OLD RC

HIGHWAY BRIDGE THROUGH PSD TESTING

O.S. Bursi1 , R. Ceravolo

2, L. Di Sarno

3, M. Erdik

4, F.Paolacci

5,

M. Sartori6, P. Pegon

7


2Politecnico di Torino, Italy

3University of Sannio, Italy;

4Koeri, Boğaziçi University, Turkey

5University Roma Tre, Italy;

6Alga Spa, Italy;

7Joint Research Center, Italy

The seismic vulnerability assessment of existing and new lifeline systems, especially

transportation systems, is becoming of paramount importance in resilient social communities.

Transportation systems were built worldwide mainly in the late 60s and early 70s; they were

designed for gravity loads and were often equipped with plain steel bars. As a consequence

most bridges are not detailed for seismic loads and hence their structural performance is

generally inadequate under earthquake ground motions. The existing state-of-art in the field

of seismic performance of existing bridges is scarce. It is therefore urgent to propose reliable

procedures for assessing the seismic vulnerability of existing bridge structures. The aim is to

provide comprehensive guidelines for the seismic assessment and retrofit of existing bridges.

The “Retro” Transnational Access project funded by the European Commission within the

Series-project aims at studying the seismic behaviour of existing reinforced concrete (RC)

bridges and the effectiveness of innovative retrofitting systems. The research activity focuses

on experimental and numerical investigations of old bridges, designed mainly for gravity

loads. To this aim, the seismic vulnerability of an existing Italian viaduct with portal frame

piers (Rio Torto Viaduct) is evaluated and an isolation system is designed using both

yielding-based and friction-based bearings. An experimental test campaign is being

performed at ELSA Laboratory of JRC (Ispra, Italy). Two specimens (scale 1:2.5), with two

(total height is 6.8 m) and three (total height is 11.2 m) transverse girders, one-bay reinforced

concrete frame are being built and tested using the pseudo-dynamic test technique with sub-

structuring. The modelling of the entire viaduct is considered along with the non-linear

behaviour of each pier, due to bending, shear on the transverse beams and strain penetration

effect at the column bases. During the test the following configurations are considered: 1)

retrofitted viaduct using Friction Bearings, and 2) the “as-built” viaduct imposing a medium

damage level. For each phase of the experimental campaign a proper dynamic identification

is performed. Natural records selected on the basis of a specific hazard analysis are used

during the tests. The comprehensive numerical investigations and the first results of the PsD

campaign have shown the high vulnerability of the sample bridge; a passive protection

system is thus deemed necessary. The isolation systems have been designed and

characterized, whereas the isolated configuration of bridge will be tested soon.


10

PSEUDO-DYNAMIC TESTING OF A PIPING SYSTEM

BASED ON MODEL REDUCTION TECHNIQUES

Md. S. Reza, Giuseppe Abbiati, Alessio Bonelli, Oreste S. Bursi


Over the last three decades, Pseudo-Dynamic Testing (PDT) with Dynamic Substructuring

(DS) has gained significant popularity due to its applicability in testing several types of

nonlinear structures/systems. In a PDT with DS, a heterogeneous model of the emulated

system is created by combining a Physical Substructure (PS) with a Numerical Substructure

(NS) that describes the remainder of the system. However, until today, a major drawback of

this method has been considered its inadequacy to test a system containing distributed

masses. With an intention to overcome this limitation, this paper presents an extension of the

PDT with DS technique by enabling its application to structures having distributed masses. In

this respect, we describe the implementation of the PDT with DS on a typical petrochemical

piping system. Some challenges faced during the implementation are shown and strategies

adopted to overcome these problems are described. In greater detail, we show the

substructuring technique used and how we minimized relevant errors generated owing to this

substructuring. We discuss a number of model reduction techniques adopted for the reduction

of the PS and the earthquake forces to the coupling nodes. Moreover, a stability analysis of

the coupled system is proposed. Finally, experimental results are presented and the reliability

of the pseudo-dynamic testing technique is discussed for this application.


11

ADVANCED HYBRID SIMULATION FRAMEWORKS

FOR CIVIL STRUCTURES

Brian M. Phillips1 and B.F. Spencer, Jr.

2

1University of Maryland;

2University of Illinois

Hybrid simulation is a cost effective alternative for the experimental evaluation of civil

structures. It combines experimental testing and numerical simulation with the dynamic

behavior of the structure represented numerically. Through substructuring, the total structure

can be partitioned into experimental and numerical substructures to represent the complete

dynamic behavior of the system. The component of interest, experiencing damage or other

complex nonlinear behavior, can be experimentally represented while the more easily

modeled components represented numerically. Substructuring also allows for multiple

platforms to independently represent each component. With multiple independent platforms,

a framework is required to coordinate the reliable exchange of information during the hybrid

simulation. This paper will review both traditional hybrid simulation and recent advanced in

real-time hybrid simulation (RTHS). UI-SimCor is software developed at the Univ. of Illinois

NEES facility to coordinate multiple platforms during traditional hybrid simulation. The

hybrid simulation framework incorporating UI-SimCor software as the coordinator is split

into three categories: (1) experimental modules consisting of servo-hydraulic systems,

specimens, sensors, and data acquisition systems; (2) computational modules consisting of

numerical simulation software, and (3) observer modules to coordinate with outside networks

and allow for geographically distributed hybrid simulation. The UI-SimCor software and

framework has proven successful for the hybrid simulation of curved bridges under complex

seismic loading, semi-rigid steel frames, and multiple education and outreach programs as

well as the geographically distributed hybrid simulation of a bridge focused on soil-structure-

foundation interaction. When the dynamic response of the experimental component is

deemed significant and difficult to represent numerically, the experimental component must

be tested in real-time. This necessitates the entire hybrid simulation to be run in real-time

(i.e., RTHS). The coordination of hybrid simulation components becomes time sensitive and

the computational side of the RTHS must be designed for real-time performance. In lieu of a

flexible framework such as provided by UI-SimCor, application specific coordination is

typically developed with only the necessary components included. Dedicated real-time digital

signal processors are used for numerical integration and actuator control. The interface

between experimental and numerical components, namely servo-hydraulic system, is also

designed for speed. However, these actuators contribute most significantly to the time lag in

the RTHS loop of action and reaction. Actuator control techniques must be developed to

compensate for these actuator dynamics such that they do not influence the results of the

RTHS. A framework for RTHS has been developed at the University of Illinois incorporating

high-performance hardware and software. To provide accurate tracking of the desired

trajectories, a model-based actuator control technique is incorporated in the framework. The

framework has proven successful at testing multi-degree-of-freedom systems with an MR

damper as the experimental component. Furthermore, the technique has been extended to

include multi-actuator systems for the testing of complex experimental components.


12

GEOGRAPHICALLY DISTRIBUTED CONTINUOUS HYBRID SIMULATION

Ferran Obón Santacana and Uwe E. Dorka

University of Kassel, Germany

One of the tasks within the FP7 SERIES Project was the creation of a European Platform for

Geographically Distributed Tests. This platform was envisioned to be able to deal with

different protocols and algorithms so that its users and facilities were not restricted to one

specific protocol. The platform should also prove the possibility of performing

geographically continuous distributed tests since up to now the distributed tests between two

different countries that have been performed were stop and go. However, though the use of

an efficient sub-structure algorithm, continuous tests can be performed using standard

network connections.

With that in mind several activities were performed at the University of Kassel that involved

not only European partners, like the University of Oxford, but also other facilities and

networks around the world, namely: the University of California at Berkeley, the Hybrid

Simulation Testing Center (HYSTEC) in South Korea and the National Center for Research

on Earthquake Engineering (NCREE) in Taiwan. With each partner continuous time-scaled

hybrid simulation tests with a non-linear sub-structure were performed exploring the different

available protocols. In addition to such experiments, the possibility to carry out continuous

sub-structure testing with large numerical models (with the order of a thousand degrees of

freedom) using the Linux Cluster at the University of Kassel was studied proving the

extensibility of the platform to large and complex numerical models.


13

DYNAMIC SUBSTRUCTURING FOR SOIL STRUCTURE INTERACTION

USING A SHAKING TABLE

Zhenyun Tang1, Matthew Dietz

2, Zhenbao Li

3, Colin Taylor

2

1 Kyoto University, Japan

2 University of Bristol, UK

3 University of Technology, Beijing, China

The experimental investigation of soil-structure interaction phenomena is typically performed

on a shaking table with a model foundation-structure system embedded in a soil container. As

the size and power of the shaking table limits the size of the specimen, only small scale

models can be tested using this method. A novel structural testing method to overcome this

disadvantage is supplied by the real-time dynamic substructuring. This paper develops a real-

time substructuring testing system for the seismic simulation of soil-structure interaction

using a shaking table. The soil-foundation system was modelled numerically, the

superstructure was modelled physically, and the shaking table was used to reproduce the

interface response. A new model-based control strategy called Full-State Compensation via

Simulation (FSCS) is used to compensate for the dynamics of shaking table that is a

conjunction of Inverse Dynamics Compensation via Simulation and full-state feedback. The

results from an entirely physical test are compared to those from a real-time dynamic

substructuring test in order to verify the validity of this method.


14

REAL-TIME HYBRID TESTING FOR SOIL-STRUCTURE INTERACTION:

AN ADAPTIVE SIGNAL PROCESSING FRAMEWORK

Vasileios K. Dertimanis, Harris P. Mouzakis, Ioannis N. Psycharis

National Technical University of Athens, Greece

This study investigates the problem of conducting real – time hybrid tests for soil – structure

interaction using shaking tables. To this, a novel framework was formulated on the basis of

adaptive signal processing and parameter estimation methods. The former were utilized in

order to compensate the dynamics of the shaking table, while the latter were used for the

compensation of the total transfer delay.

Specifically, an adaptive inverse control scheme was designed and placed between the

numerical substructure and the transfer system, aiming at “canceling” the dynamics of the

shaking table. It follows that the cascade of the adaptive controller and the shaking table

becomes a delayed unit impulse response. To compensate this delay, a multi – step ahead

predictor was estimated by performing parametric and non – parametric identification on the

specimen (physical substructure).

The applied methodology is characterized by two additional innovative features: (1) it

replaces the traditional displacement command to the physical substructure by the

acceleration one. This allows a wider response spectrum to be actually implemented to the

specimen; and (2) it replaces the traditional load cell sensor for force feedback by an

accelerometer that is placed on the specimen mass.

The method was applied to a simple, linear SDOF structure (physical model) on a

horizontally deformable soil, reducing, thus, the SSI problem to two – DOF. Two specimens

were tested, with periods of 0.5 s and 0.2 s, both having a specimen – to – foundation mass

ratio equal to 4. While the results of this implementation scheme were promising, the

corresponding adaptation process requires further investigation, in order to avoid effects that

alter its performance.


15

TOWARDS AN IMPLEMENTATION OF THE FHT TECHNIQUE FOR SSI

SYSTEMS USING NONLINEAR MACROELEMENTS

Charisis T. Chatzigogos1, Matt Dietz

2, Alain Pecker

1, Zhenyun Tang

2,3

1Géodynamique et Structure, France

2University of Bristol, UK 3Kyoto University, Japan

Joint Research Activity 3 of SERIES has been concerned with experimental and theoretical

investigations of interacting soil-structure systems under earthquake loading. In one of the

subtasks of this activity, the University of Bristol and Géodynamique & Structure (GDS)

have collaborated towards an implementation of the first variant of the Fast Hybrid Testing

technique using nonlinear foundation macroelements as the numerical substructure.

Efforts towards this goal have been twofold: regarding shaking table control, research at the

Univ. of Bristol has been principally concerned with the development of a novel controller

for shaking table sub-structuring capable of dealing with issues of shaking table dynamics

such as phase lag and magnitude error within a frequency range of interest. The developed

novel controller, called Full State Compensation via Simulation (FSCS), has been based on

inverse dynamics compensation and full-states feedback control techniques and has been

shown to exhibit enhanced stability and accuracy properties with respect to conventional

compensation controllers. The controller has thus been introduced in an integrated single

degree-of-freedom shaking table sub-structuring test system allowing for real-time sub-

structuring, particularly adapted for high-frequency, low-damping substructures and high-

magnitude excitation frequencies. In a parallel activity, GDS has been focusing on the

development of a nonlinear dynamic macroelement for shallow foundations. The scope has

been to propose a formulation encompassing the main sources of nonlinear behavior at the

soil-foundation interface (in particular soil plasticity, foundation uplifting and relative sliding

along the interface), which will be general enough to be used for different soil types and

shallow foundation geometries. Introduction of the foundation macroelement can be thought

of as a degree-of-freedom condensation procedure, in which the entire foundation and soil

domain are replaced by a link element with three (2D kinematics) or six (3D kinematics)

degrees-of-freedom. The interest in using macroelements in FHT is that a quasi-simultaneous

resolution of the nonlinear constitutive behavior of the numerical substructure can be

achieved, respecting the inherent constraints of real-time sub-structuring testing.

The two developments have been brought together in a realization of the first variant of the

FHT technique, in which the superstructure is modeled physically on the shaking table

whereas the foundation and soil substructure are modeled numerically. Using the novel FSCS

controller for the shaking table dynamics and introducing the foundation macroelement as the

numerical sub-structure, it has been feasible to test single degree-of-freedom model structures

under pure seismic loading and obtain qualitative features of non-linear SSI such as wide

force-displacement loops at the foundation level and residual foundation displacements at the

end of the excitation.

Session 2 – SERIES TA to Centrifuge Facilities

16

SERIES Transnational Access to

Centrifuge Facilities

Session 2

Tuesday, 28 May 2013


17

CENTRIFUGE MODELING OF DYNAMIC BEHAVIOR OF BOX SHAPED

UNDERGROUND STRUCTURES IN SAND

Deniz Ülgen1, Selman Sağlam

2,M. Yener Özkan

3, Jean Louis Chazelas

4

1Mugla Univrsity (MSKÜ), Turkey

2Adnan Menderes University in Aydin (ADU), Turkey 3Middle East Technical University (METU), Turkey

4IFSTTAR, Division Reconnaissance et Mécanique des Sols, France

Seismic safety of underground facilities such as pipelines, culverts, subways and tunnels

becomes an essential requirement for continuing economic and social development. Many

engineers earlier thought that the underground structures had been inherently safe against

earthquakes, but then, especially after the failure of some underground facilities during 1995

Kobe, Japan, 1999 Kocaeli, Turkey and 1999 Chi Chi, Taiwan earthquakes the safety

evaluation of the underground structures become a major concern of the engineers.

This research aims to investigate the dynamic response of box shaped underground structures

buried in dry sand. For this purpose, a series of centrifuge tests are carried out under

harmonic sinusoidal motions by considering the nonlinear behavior of both structure and

surrounding soil. The dynamic earth pressure is one of the most important parameters in the

seismic design of culverts. However, there is no an established methodology clarifying the

mechanism and evaluations of the dynamic earth pressures. Hence, response acceleration in

the ground, dynamic strains of the buried models and dynamic soil pressures acting on the

buried model are examined with special reference to the dynamic soil structure interaction.

Specific variables considered in this study are input motion characteristics and rigidities of

buried box structures. Three different models are used in the tests with varying rigidities.

Results of the experiments are evaluated in order to make an assessment on load transfer

mechanism between the soil and buried structure under different motions. Furthermore, the

findings of this study are compared with the predictions of closed-form solutions

recommended by Penzien (2000) and Huo et al. (2006).


18

INVESTIGATION OF THE SEISMIC BEHAVIOUR OF SHALLOW

RECTANGULAR UNDERGROUND STRUCTURES IN SOFT SOILS

USING CENTRIFUGE EXPERIMENTS

Grigorios Tsinidis1, Emmanouil Rovithis

2, Kyriazis Pitilakis

3, Jean‐Louis Chazelas

4

1Aristotle University of Thessaloniki, Greece

2Earthquake Planning and Protection Organization, Greece

3 Aristotle University of Thessaloniki, Greece

4IFSTTAR, Division Reconnaissance et Mécanique des Sols, France

Seismic response of underground structures is explored by means of well‐documented

experimental data as part of a Transnational Access action offered by the SERIES research

project (TA Project: DRESBUS II). For this reason, a series of centrifuge tests were

performed at the geotechnical centrifuge facility of IFSTTAR in Nantes focusing on

rectangular model tunnels in dry and saturated sands and excited under a centrifugal

acceleration of 40g. The testing program aimed at investigating the seismic behaviour of

rectangular tunnels as affected by soil‐structure relative flexibility and soiltunnel interface

characteristics. Both rigid and flexible structures with smooth or rough interfaces were tested

covering a wide range of soil‐tunnel configurations. Numerical analyses of the observed

tunnel behaviour were undertaken by means of the general FE platform ABAQUS and

compared to the experimental data. The effect of salient model parameters such as the

seismic earth pressures and the shear stresses around the tunnel are discussed. The above

study is foreseen to shed some light on a set of important but unresolved issues within

seismic design of underground structures.


19

INVESTIGATION OF SEVERAL ASPECTS AFFECTING THE SEISMIC

BEHAVIOUR OF SHALLOW RECTANGULAR UNDERGROUND STRUCTURES

IN SOFT SOILS

Tsinidis, G.1, Heron, C.

2, Madabhushi S.P.G.

1, Pitilakis, K.

1 & Stringer, M.

1

1Aristotle University of Thessaloniki, Greece

2University of Cambridge, UK

Extended underground structures (i.e. tunnels, subways, underground parking lots etc.)

constitute significant components of the transportation networks and the built environment.

During past earthquakes several cases of extensive damage and even collapse have been

reported for these types of structures, with that of the Daikai subway station in Kobe that

collapsed during the major 1995 Hyogoken‐Nambu earthquake, being the most interesting.

The specific features of underground structures make their seismic behavior very distinct

from aboveground structures. There is a lack of knowledge regarding several crucial issues

affecting this behavior (i.e. dynamic earth pressures on the side‐walls of a totally embedded

structure, seismic shear stresses around the structure‟s perimeter etc.), thus making seismic

design very tricky. Actually, for the evaluation of the seismic response of underground

structures, several methods may be found in the literature, based on different levels of

complexity. The results of these methods may substantially deviate, even under the same

assumptions, indicating the lack of knowledge regarding the phenomenon. To this end, a set

of three dynamic centrifuge tests have been performed at the University of Cambridge

(UCAM) jointly with Aristotle University of Thessaloniki (AUTH) on square tunnel models

embedded in dry sand. The tests were carried out at the geotechnical centrifuge facility of

UCAM, within the Transnational Access Activities of SERIES (TA project: TUNNELSEIS).

Two tunnel‐models were studied; a “rigid” and a “flexible” one, the latter deformed during

swing up and collapsed during an earthquake. The produced experimental data is used to

better understand the seismic behavior of non‐circular embedded structures. The data

obtained will be also used to validate advance numerical models and to improve the design

methods. The test set ups and the experimental procedure are briefly presented along with

representative experimental data. Among the main results we observed:

An important effect of the acceleration wave field on the tunnel response.

Presence of complex deformation modes for the rigid tunnel (rocking vibration),

usually precluded in the simplified design methods (pure racking deformation

assumption).

Residual values for the earth pressures on the sidewalls of the tunnels, caused by the

soil plastic deformations and the soil densification.

Residual values for the internal forces (both in terms of axial forces and bending

moments), caused by the soil plastic deformations, the soil densification and, to some

extent, due to small amounts of sliding on the soil‐tunnel interface.


20

EXPERIMENTAL VERIFICATION OF SHALLOW FOUNDATION

PERFORMANCE UNDER EARTHQUAKE-INDUCED LIQUEFACTION

Karamitros D.K.1, Cilingir U.

2, Bouckovalas G.D.

1, Madabhushi S.P.G.

2,

Papadimitriou A.G.3, Haigh S.K.

2

1National Technical University of Athens (NTUA), Greece

2University of Cambridge (UCAM), UK 3University of Thessaly (UTh), Greece

The seismic performance of a square footing, resting on an over-consolidated clay crust,

overlying a liquefiable sand layer, is examined herein, through the performance of a series of

three centrifuge experiments, conducted at the Schofield Centre of Cambridge University

Engineering Department (CUED). The scope of these experiments is to verify the beneficial

effect of the existence of a surficial non-liquefiable layer (over-consolidated clay crust) on

the response of the footing. In addition, these experiments aim at exploring whether this non-

liquefiable layer allows for a viable performance-based design methodology for shallow

foundations, without the need of implementing any soil treatment on the underlying

liquefiable sand. For this purpose, different thicknesses H of the clay crust were

parametrically used, varying from H=0.65 to 1.50B, with B being the footing‟s width (equal

to 3m in prototype scale).

Each test was performed in three stages:

a) The centrifugal acceleration was raised to 50g, in steps of 10g, allowing adequate

time for the consolidation of the clay layer.

b) Twenty (20) uniform cycles of harmonic excitation, with a peak acceleration of

amax=0.25g were applied at the base of the equivalent-shear-beam container. During this

stage, excess pore pressures were developed in the sand layer, resulting in the accumulation

of seismic settlements of the footing.

c) Immediately after the end of shaking and before the dissipation of excess pore

pressures, a hydraulic piston was used to increase foundation contact pressure, until bearing

capacity failure, in order to measure the (degraded) post-shaking bearing capacity. It should

be underlined that there are no published experimental data, regarding the liquefaction-

induced degradation of bearing capacity of shallow foundations and this is first time such a

study was attempted anywhere in the world.

Following a presentation of the testing configuration and the mechanical properties of the two

soil layers (clay crust and sand) in this paper, the experimental results are presented and

critically evaluated. The basic mechanisms of foundation performance are analyzed, during

as well as following shaking, while emphasis is given to the effect of non-liquefiable clay

layer thickness H on the accumulation of foundation settlements.


21

CENTRIFUGE MODELLING OF THE PERFORMANCE OF LIQUEFACTION

MITIGATION MEASURES FOR SHALLOW FOUNDATIONS

Andreia Marques1, Paulo Coelho

1, Stuart Haigh

2, Gopal Madabhushi

2

1University of Coimbra, Portugal 2University of Cambridge, UK

Earthquake-induced liquefaction is a major concern for structures built on saturated deposits

of cohesionless soils in seismically active regions, as it often causes failure of critical

structures and can lead to severe human and economic losses. Destructive consequences of

this phenomenon were continue to be witnessed from 1964 Alaskan and Niigata earthquakes

to more recent 2011 Tohuku earthquake and 2012 New Zealand earthquakes. During the past

decades, intensive efforts have been made to understand the mechanism of liquefaction and to

develop liquefaction resistance measures to enhance the performance of foundations during a

given seismic event. Centrifuge modelling has been proving its merits as a research tool to

facilitate progress in this field.

An on-going investigation at the Schofield Centre of Department of Engineering, University

of Cambridge, UK, focuses on the performance of shallow foundations susceptible to seismic

liquefaction, which is a particularly important research topic with large practical interest.

Three centrifuge modelling experiments were carried out to investigate the magnitude of

liquefaction effects on shallow foundations, under different conditions, and to assess the

performance of innovative mitigation techniques for this problem. This paper will present a

detailed analysis of the different results obtained during the tests and compare the influence

of the bearing pressures imposed on the ground by two different footings and the

performance of different mitigation techniques. A narrow densified zone under the footing

and an hybrid technique using densification and high-capacity vertical drains will be

considered in detail. The excess pore pressure measured during and after the seismic event

will be presented and discussed to evaluate and compare the results obtained in the different

situations considered in the modelling. Also, the accelerations measured at different positions

in the liquefiable soil and in the structures tested will be presented to better understand the

effects of using a densified zone, combined or not with vertical drains. Finally, the

settlements of the footings obtained in every case under study will be presented and

discussed, not only during the seismic event but also in the post-seismic phase, to investigate

the importance of consolidation settlements caused after soil liquefaction.

Clarification of the issues herein identified is a fundamental requirement to better understand,

predict and enhance the behaviour of shallow foundations built on liquefiable ground, which

can actively contribute to develop innovative liquefaction resistance measures that offer

improved cost-benefit ratios.


22

CENTRIFUGE MODELING OF PAIRS OF FLEXIBLE RETAINING WALLS IN

SATURATED SAND UNDER SEISMIC ACTIONS

(TA PROJECT: PROPWALL)

Stefano Aversa1, Luca de Sanctis

1, Rosa Maria Stefania Maiorano

1,

Michele Tricarico1, Giulia Viggiani

2, Riccardo Conti

2, Gopal Madabhushi

3, Mark Stringer

3,

Charles Heron3

1Università degli Studi di Napoli “Parthenope”, Italy 2Università degli Studi di Roma Tor Vergata, Italy


The centrifuge tests carried out under the research project PROPWALL at the Schofield

Center of the Cambridge University Engineering Department are presented and discussed.

The tests were carried out on flexible retaining walls embedded in saturated sand excited by a

train of quasi-sinusoidal waves. The piezometric head of the porosity fluid, methyl cellulose,

was at dredge level. Two tests were carried out on pairs of flexible retaining walls with one

level of support near the top, while the remaining two tests were performed on cantilevered

walls. The experimental equipment, the model preparation and the monitoring devices are

described in detail. The results are presented in terms of accelerations, deflections, bending

moments and excess pore pressures, as monitored through the devices installed on the walls

and within the soil mass. A preliminary interpretation of the observed behaviour is also given.


23

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS OF NONLINEARITY IN

SOILS USING ADVANCED LABORATORY-SCALED MODELS:

AN APPLICATION TO THE ROME HISTORICAL CENTRE

(TA PROJECT: ENINALS)

F. Bozzano1, A. Bretschneider

1, A.C. Giacomi

1, S. Martino

1, G. Scarascia Mugnozza

1, S.

Escoffier2, L. Lenti

2, J-L. Chazelas

2, C. Favraud

2, D. Macé

2

1 “Sapienza” University of Rome, Italy

2 IFSTTAR, France

The SERIES TA project “Experimental and Numerical Investigations of Nonlinearity in soils

using Advanced Laboratory-Scaled models” (ENINALS) was focused on the centrifuge

modeling of seismically-induced strains vs. stratigraphic features. These last ones were

specifically referred to the presence, thickness and location of clay levels representing the

alluvial deposits of the Tiber River in Rome historical centre, which is exposed to Mw>6

earthquakes from the Central Apennine chain with epicentral distances shorter than 100 km.

Several studies have been focused on the amplification effects of the Tiber alluvial deposits

in Rome historical centre. Moving from this consolidated knowledge, the main goal of

ENINALS was to investigate possible non-linearity effects associated with the worst seismic

actions in Rome and, namely, related to the stratigraphic juxtaposition of more deformable

clayey-silts, and of stiffer sands or sandy-silts. A laboratory-scaled centrifuge modeling with

a dynamic action was associated to the numerical simulation of non linearity by 1D-3C

approaches. 4 samples were tested at reduced scale in the centrifuge, representing two

homogeneous soil columns (clayey and sandy column respectively) and two heterogeneous

soil columns, including a clay level between two sand beds representing a 5m and a 10m clay

layer respectively. The applied dynamic input represents the maximum expected seismic

action in Rome. It was reproduced at the shaking device as: i) a natural time history, ii) an

equivalent sinusoidal signal and iii) a multifrequential equivalent signal derived by the

recently proposed LEMA_DES approach. The effects of nonlinearity due to seismic shaking

in the considered heterogeneous soil columns was also simulated by the 1D-3C finite

difference numerical code SWAP, implemented by IFSTTAR. The strain effects obtained for

the homogeneous and for the heterogeneous soil columns were compared and a Shear Strain

Concentration Index (SSCI) was computed to define a differential strain rate. Findings show

i) a main role of soil heterogeneity in conditioning the shear strains and their distribution

along the vertical soil profiles and ii) drive to a quantitative approach to evaluate the

reliability of 1D vs. 2D-3D conceptual modeling in complex geological setting, as in the case

of alluvial valleys filled by heterogeneous soils.

Session 3 – US-NEES Developments

24

US-NEES Developments

Session 3

Wednesday, 29 May 2013


25

THE GEORGE E. BROWN, JR., NETWORK FOR EARTHQUAKE ENGINEERING

SIMULATION (NEES): ACCELERATING IMPROVEMENTS IN SEISMIC DESIGN

AND PERFORMANCE BY SERVING AS A GLOBAL COLLABORATORY

FOR DISCOVERY AND INNOVATION

Julio Ramirez

Purdue University, USA

The George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) is a

network of 14 shared-use laboratories (https://nees.org/sites-mainpage/laboratories)

connected by a cyberinfrastructure that fosters collaboration in research and education

(https://nees.org/).

In the 9th year of official operations, over 400 multi-year, multi-investigator projects have

gone through NEES, yielding many advances in earthquake engineering and a wealth of

valuable experimental data. At the core of the NEES cyberinfrastructure is the NEES

platform for collaboration, NEEShub, providing convenient access to tens of thousands of

users from over 190 countries to the NEES central data repository (Project Warehouse). The

NEEShub hosts tools for data visualization, analysis, hybrid simulation, education, and

collaboration. In this paper a small sample of the many research, outreach, information

technology, and educational accomplishments of NEES are described. These examples

illustrate the impact of the efforts of the NEES community towards improving the resilience

of our society against earthquakes and tsunamis.

https://nees.org/sites-mainpage/laboratories

https://nees.org/


26

PROMOTING RE-USE OF EARTHQUAKE ENGINEERING DATA

THROUGH THE NEESHUB

JoAnn Browning

University of Kansas, USA

Over the past several decades, the civil engineering profession has amassed vast amounts of

quantitative data obtained from numerical and physical simulations of seismic events. But the

bulk of the information lives only in printed media that are difficult and time consuming to

use. And much of the generated data are not available in journals because page limits have

forced researchers to leave out everything but the most pertinent facts. Further, the limited

data that are available in digital format are cumbersome to use because formats vary from

source to source.

The result is an inefficient method for studying the behavior of structures and soils, with

these common challenges:

Data pertaining to a common design or evaluation issue have to be compiled through

time‐consuming searches, requiring researchers to explore the ever-increasing

numbers of journals almost one by one;

Researchers may need to request additional data from publication authors;

Data plots and tables from publications must be digitized, essentially using manual

processes; and

Engineers with similar project needs must endeavor to collect and analyze the same

sets of data.

For the past 10 years, the George E. Brown Jr., Network for Earthquake Engineering

Simulation (NEES) has helped to bring data sets to the larger community. NEES‟ objective is

to assist researchers, practicing engineers, and code and guideline developers as they work on

innovations for minimizing damage caused by earthquakes or tsunamis. NEES operations are

managed by the NEES Community and Communications (NEEScomm) Center, which

manages the NEES cyberinfrastructure (hosted on NEEShub) and a nationwide network of 14

laboratories (www.nees.org/sites-mainpage) that are available to researchers from U.S.

universities and firms. Research at the NEES facilities is funded by the NSF; by other federal,

state, and local agencies; by private industry; and under the partnerships that NEES has

cultivated with investigators, research facilities, and agencies in Japan, Taiwan, Canada, and

China. To date, almost 400 multi‐year, multi‐investigator projects have been completed or are

in progress at NEES sites. The research data has become available in a digital medium, but

there is still a challenge to promote easy re-use of the data.

NEES has developed a number of initiatives through the NEEShub to help promote data re-

use in its most efficient formats. This presentation focuses on several of these initiatives,

including: establishment of DOI‟s for easy reference and promotion of datasets, NEEShub

Databases, visualization tools, and new data search mechanisms.


27

RE-USE OF EXPERIMENTAL EARTHQUAKE DATA FOR RESEARCH:

THREE ILLUSTRATIVE EXAMPLES

John W. van de Lindt

Colorado State University, USA

One of the key contributions of the George E. Brown Network for Earthquake Engineering

Simulation (NEES) lies in the data archival process, particularly the ability of earthquake

engineering researchers to utilize experimental data for research beyond the original intent of

the experiment. Although this seems straightforward in concept, the ability to utilize

experimental data based on only what is archived presents a number of challenges. For

successful data re-use the following are key: (1) data specific to the purpose of the new study

must be available; (2) the needed accuracy which may not be the accuracy utilized in the

original experiment must be available and be able to be identified; and (3) the ability to

properly cite a journal paper or report from the original experiment should be readily

identifiable. In this presentation, three illustrative examples that re-use data from NEES

experiments in 2006, 2007, and 2009, focusing on a wood building shake table test, a steel

moment frame shake table collapse test, and reversed cyclic tests on reinforced masonry

shear- and transverse-walls, are applied to current or recent research studies. The first

examples on a wood and steel building utilize the global hysteresis to develop collapse

models for aftershock studies, while the latter example calibrates a system level masonry

model for use in seismic fragility development. In the wood example, the data from a two-

story light-frame wood building tested at NEES@UB in 2006 was utilized to develop a

global hysteretic model with one-degree-of-freedom at each story. The collapse model

developed was used to assess aftershock risk of a typical light-frame wood building with

future integration into a performance-based seismic design framework. The steel moment

frame test data was used for a similar purpose but to model typical steel frame buildings. The

reinforce masonry wall data was used to calibrate both shear wall and transverse wall

hysteretic models to implement them into SAPWood, a software package developed within

an earlier NEES project. Finally, both challenges and successes of using data from these three

experimental programs will be presented.


28

COMMUNICATING EARTHQUAKE ENGINEERING: THE EDUCATION,

OUTREACH, AND TRAINING ACTIVITIES OF THE GEORGE E. BROWN, JR.

NETWORK FOR EARTHQUAKE ENGINEERING SIMULATIONS

Barbara Fossum

Purdue University, USA

The goal of broadening participation of underrepresented groups in engineering has long been

a priority at the National Science Foundation, and is repeatedly referenced in major policy

documents. Underrepresented groups in engineering are currently defined as women,

Hispanics, African Americans, Pacific Islanders and Native Americans. The NEES network

is committed to increasing the diversity of the network across all areas. Additionally the

network is inspiring and preparing the next generation of earthquake engineers through

programs involving Research Experience for Undergraduates. In collaboration with the

National Science Foundation (NSF), the Research Experience for Undergraduates (REU)

program is a six-week, hands-on, paid research experience for undergraduate students.

During this period, students perform research with NEES scientists, participate in education

workshops, attend scientific lectures, and develop new skills and interests in earthquake

engineering.

This talk will provide an overview of some of the programs implemented at NEES for

educating the next generation of earthquake engineers and increasing awareness of the NEES

network. Specific examples include opportunities for increasing the participation of

underrepresented groups, outreach to K-12 education, research opportunities for

undergraduate students and transferring research results to the practicing engineering

community. Participation of minority serving institutions will also be discussed.


29

DAMPING ESTIMATION FROM SEISMIC RECORDS

Dionisio Bernal

Northeastern University, USA

Extraction of damping ratios from input-output measurements is a standard problem in

identification and exact results are obtained by all theoretically consistent algorithms when

the data generating system is viscously damped, linear, time invariant and the input-output

records are noise free. In practice, however, these assumptions are never entirely satisfied

and, as a consequence, identified damping ratios are random variables. In the particular case

of seismic analysis it is well known that identified damping values have relatively high

variance and it is shown here that this is a consequence of the low Fisher information

contained in the response; a significant contributor being the relatively short durations of

seismic signals. Notwithstanding the difficulties, values for damping are needed to formulate

predictive models and expressions to estimate the expected value for buildings have been

proposed through the years. Although not explicitly stated in most cases, these expressions

are based on analyses that reflect dissipation within the structure, as well as energy loss

through the soil structure interface. This paper summarizes recent work on characterizing the

uncertainty in the estimation of damping, discusses the issue associated with isolating

structural characteristics from those of the structure-soil system, and presents some new

statistical expressions for expected value of the first mode damping ratio derived from

analysis of a large collection of seismic responses.

Session 4 – SERIES Networking Activities: DDB & Qualification of RI

30

SERIES Networking Activities:

Distributed Database and Qualification of Research

Infrastructures

Session 4



31

A FACETED LIGHTWEIGHT ONTOLOGY FOR EARTHQUAKE ENGINEERING

RESEARCH PROJECTS AND EXPERIMENTS

Md. Rashedul Hasan, Feroz Farazi, Oreste S. Bursi, Md. Shahin Reza


With the invention of the Semantic Web, computing paradigm is experiencing a shift from

databases to Knowledge Bases (KB), in which ontologies play a major role in enabling

reasoning power that can make implicit facts explicit to produce better results for users. In

addition, KB‐based systems provide mechanism to manage information and semantics thereof

that can make systems semantically interoperable and as such can exchange and share data

between them. To overcome the interoperability issues and to exploit the benefits offered by

the state of the art technologies, we moved to the KB based system. Essentially, we have

developed an earthquake engineering ontology using a faceted approach with a focus on

research project management and experiments. Following the validation of the ontology by a

domain expert, it was published in the knowledge representation language RDF and

integrated to the generic ontology WordNet. The experimental data coming from, inter alia,

cyclic and pseudo‐dynamic tests were also published in RDF. We used Jena, OWLIM and

Sesame tools for publishing, storage and management, respectively. Finally, integrating the

tools, ontologies and data, we developed a system to evaluate the effectiveness of the

approach and in fact we found quite convincing and satisfactory results.


32

THE SERIES DISTRIBUTED DATABASE:

ARCHITECTURE AND IMPLEMENTATION

I.L. Martinez1, I. Ioannidis

2, C. Fidas

2, M. Williams

1, P. Pegon

3

1University of Oxford, UK

2University of Patras, Greece

3Joint Research Centre, Italy

The European scientific community is currently highly fragmented, with each laboratory

holding experimental data, stored in some cases in a non-structured way. As a consequence,

the dissemination and use of experimental results outside of the laboratory where they are

produced can be problematic. This leads to wasteful duplication of tests and ultimately limits

the impact of earthquake engineering research on practice, innovation and earthquake risk

mitigation. One part of the SERIES Networking Activities aim at facilitating the exchange of

data and data communication among research infrastructures in Europe providing access to

data by means of a distributed database. The scope was not to build a central database where

local databases would either migrate or merge, but instead to provide centralised access to

database nodes that are distributed over a network that are able to dialog with a central portal

in a uniform manner. To this end, database nodes use Web Services, to cast their data into a

uniform standard format for uploading and downloading. The paper concentrates on the

architecture and the implementation of the Distributed Database.


33

THE SERIES DISTRIBUTED DATABASE: EXCHANGE FORMAT,

LOCAL DBS AND CENTRAL PORTAL INTERFACE

A. Bosi1, S. Bousias

2, J.L. Chazelas

3, M. Dietz

4, M.R. Hasan

5, S.P.G. Madabhusi

6,

A. Prota7, T. Blakeborough

8, P. Pegon

9

1Vienna Consulting Engineers, Austria;

2University of Patras, Greece

3IFSTTAR, France;

4University of Bristol, UK



7University of Naples, Italy;

8University of Oxford, UK

9Joint Research Center, Italy

The European scientific community is currently highly fragmented, with each laboratory

holding experimental data, stored in some cases in a non-structured way. As a consequence,

the dissemination and use of experimental results outside of the laboratory where they are

produced can be problematic. This leads to wasteful duplication of tests and ultimately limits

the impact of earthquake engineering research on practice, innovation and earthquake risk

mitigation. One part of the SERIES Networking Activities aim at facilitating the exchange of

data and data communication among research infrastructures in Europe providing access to

data by means of a distributed database.

From the User point of view, the approach is based on a scheme for the data to be exchanged

(Exchange Data Format), local databases (one prototype DB is currently deployed at various

SERIES places), interface and tools allowing populating the local DBs and a Central Portal

giving access to the SERIES data. The paper presents and discusses all these aspects.


34

QUALIFICATION OF SEISMIC RESEARCH TESTING FACILITIES

IN EUROPE

Maurizio Zola1, Fabio Taucer

2

1Consultants of P&P LMC, Italy

2JRC, Italy

The qualification of large research seismic testing facilities in Europe was one of the main

goals of the SERIES Project. SERIES‟s Networking Activity 2 aimed at creating the

conditions leading to the qualification of Structural Testing Laboratories specialising in

earthquake engineering and equipped for large scale testing. The activities in NA2 were

aimed to address the assessment criteria for technical competence of the research

laboratories, based on repeatability and reproducibility of the testing activities.The NA2

activity was broken down in four Tasks: i) Evaluation and impact of qualification of

experimental facilities in Europe; ii) Assessment of testing procedures and standards

requirements; iii) Criteria for instrumentation and equipment management; iv) Development

and implementation of a Common Protocol for qualification.

The emergence of performance based engineering (PBE) approaches in earthquake

engineering offers an opportunity to rethink laboratory test approaches by tailoring the test

program to achieve performance outcomes that are explicitly defined for the particular test

specimen. To implement the Qualification a Draft Common Protocol covering the

Management and Technical General Requirements with a check list for the audits was

produced; moreover Specific Technical Requirements for Shaking Table Testing, Reaction

Wall Testing, On-site Testing, Data Acquisition and Processing were identified and specified

in four technical annexes to the Common Protocol.

Thus the qualification of the research testing facilities may be achieved:

• by the certification of the Management System after ISO 9001 for the Research

Engineering Activities;

• by the accreditation of the Laboratory after ISO/IEC 17025 for the Measurement

Activities;

• by the accreditation of the Laboratory after ISO/IEC 17025 with flexible scope for the

Research Testing Activities.

As far as the accreditation of the Research Testing Activities after ISO/IEC 17025 with

flexible scope the Laboratory (Supplier of tests) should receive a Testing Specification issued

by the Research Engineer (Customer) and the Specific Technical Requirements (Annexes to

the Common Protocol) should be applied. This proposal for the qualification of large research

infrastructures was presented to the Laboratory Committee of EA in Oslo and to the 1st

ERNCIP Conference in Ispra.

Session 5 – SERIES TA to Shaking Table Facilities on masonry, RC and steel structures

35

SERIES Transnational Access to Shaking Table

Facilities on masonry, RC and steel structures

Session 5



36

FULL SCALE TESTING OF MODERN UNREINFORCED THERMAL

INSULATION CLAY BLOCK MASONRY HOUSES

S. Lu, A. Jäger1, L. Mendes

2, P. Candeias

2, A. C. Costa

2, E. Coelho

2, H. Degée

3, C.

Mordant3, V. Sendova

4, Z. Rakicevic

4, M. Tomazevic

5

1Wienerberger AG, Austria;

2LNEC, Portugal

3University of Liege, Belgium

4IZIIS, SS "Cyril and Methodius" University, R. Macedonia

5Slovenian National Building and Civil Engineering Institute, Slovenia

In the scope of the SERIES project Transnational Access activities, Laboratório Nacional de

Engenharia Civil (LNEC) has provided access to its 3-D shaking table to the international

construction company Wienerberger AG and to a group of European experts, in order to

perform full-scale seismic tests on an industrial solution for buildings, using modern

unreinforced thermal insulation clays block masonry.

This solution represents a very common construction method in Europe that still lacks

seismic vulnerability assessment, because most results available were carried out on cyclic

shear tests, thus the effective three-dimensional dynamic response under seismic events still

requires experimental validation.

Consequently, two full-scale mock-ups adopting different geometries were tested on the 3-D

shaking table using a series of seismic records with increasing intensity.

This paper presents the most relevant results regarding the structural response of the

specimens, e.g. the dynamic response evolution, the collapse mechanism identified and the

maximum drift values measured. The paper closes with the main conclusions extracted from

this work and with the tasks identified for future work.


37

ASSESSMENT OF INNOVATIVE SOLUTIONS FOR NON-LOAD BEARING

MASONRY ENCLOSURES

João Leite1, Paulo B Lourenço

1, Elizabeth Vintzileou

2, VasilikiPalieraki

2, António A.

Correia3, Paulo Candeias

3, Alfredo Campos Costa

3, Ema Coelho

3

1University of Minho, Portugal

2National Technical University of Athens, Greece

3LNEC, Portugal

This paper presents the results of the SERIES TA project “Masonry Enclosures”. The project

addresses the seismic performance of masonry enclosures in European countries with

moderate and high seismicity based on the experimental evaluation of the seismic response of

reinforced concrete (RC) frames with innovative solutions for masonry infill walls,

considering both the in-plane and out-of-plane behaviour of the enclosures. The recent

L‟Aquila earthquake of 2009 has underlined that the current masonry infill solutions are not

effective, as illustrated by the considerable in-plane damage and out-of-plane collapses

throughout the affected areas. Eurocode 8 addresses this issue by imposing the use of

reinforced infill solutions but fails to give design and detailing methodologies.

With the above in mind, a shake table experimental research programme was devised in order

to investigate the seismic behaviour of reinforced infill walls and how they affect the global

structural response.

The first phase of the research activity involved the seismic testing at the LNEC of a two-

storey RC infilled frame building designed to the Eurocodes and built at a 1:1.5 scale. These

frames were filled with single leaf clay bricks and reinforced plaster was placed on both sides

of the infill walls and anchored to the RC frame and masonry units. From these tests it was

possible to assess the evolution of the seismic behaviour of infills and their influence on the

RC structure through several acceleration inputs of increasing amplitude, associated to

cumulative damage limit states.

The second part of the project comprises the dynamic testing of a closed RC plane frame with

external dimensions of 6.50mx3.25m and structural elements with 0.50mx0.30m cross-

sectional dimensions. This plane frame will be tested simultaneously for in-plane and out-of-

plane dynamic actions, representing the response of a frame panel in a typical RC building at

different levels. Both motions should match a given floor response spectra, of narrow band

frequency content.

This unique testing setup was specifically designed for this test and is mainly composed of a

stiff steel caisson three-dimensional frame which moves rigidly with the shaking table. It is

fixed to the upper beam in the transversal direction, while a system of rollers allows for an

independent motion in the longitudinal direction.


38

SEISMIC BEHAVIOUR OF L- AND T-SHAPED UNREINFORCED MASONRY

SHEAR WALLS

C. Mordant1, M. Dietz

2, L. Vasseur

1, H. Degée

1

1University of Liège, Belgium


The contribution describes the results of the second phase of the SERIES project TA5 carried

out at EQUALS laboratory of University of Bristol. The experimental tests aim at

investigating (i) the influence of walls perpendicular to the seismic action ("flange-like"

behaviour) and (ii) the frame effect in load-bearing masonry structures subjected to

earthquake action. Two specimens are tested. The first specimen is made of two T-shaped

walls connected by a lintel to build up a frame. The two piers are designed so that the main

axis of the first one is perpendicular to the main axis of the second one. Thus, global torsional

effects are expected. The second specimen is a frame with two L-shaped walls as piers. The

structural system is globally symmetrical, but the connection of the "flange" (wall

perpendicular to the plan of the frame) to the "shear wall" (wall in the plan of the frame) is

different for both piers. In the first pier, flange and shear wall are glued, whereas they are

built in the second one. Different load cases are considered (gravity load acting on the flange

and/or on the shear wall). Results of the experimental tests evidence the contribution of the

link between piers and highlight a significant rocking behaviour. Depending on its position

and on the loading configuration, the flange is likely to increase the stability of the frame. It

is also showed that the torsional effects and the type of connection largely influence the

collapse mechanism. Additionally, identification of natural modes and damping ratios are

used to calibrate predictive models.


39

SHAKE TABLE TESTING OF A HALF SCALED RC-URM WALLS STRUCTURE

Marco Tondelli1, Sarah Petry

1, Igor Lanese

2, Katrin Beyer

1, Simone Peloso

2

1École Polytechnique Fédérale de Lausanne, Switzerland

2EUCENTRE, Italy

With the introduction of higher seismic design forces in the Swiss loading standard of 2003

most unreinforced masonry (URM) buildings failed to satisfy the seismic design check. For

this reason, in new construction projects, a number of URM walls are nowadays replaced by

reinforced concrete (RC) walls. The lateral bracing system of the resulting structure consists

therefore of URM walls and some RC walls which are coupled by RC slabs and masonry

spandrels. The same situation characterises a number of seismically retrofitted URM building

across Europe in which RC walls are added to the original structure to improve its behaviour.

Within the framework of the FP7-SERIES project, a four-storey RC-URM wall structures

was tested on the shake table at the EUCENTRE TREES Lab (Laboratory for Training and

Research in Earthquake Engineering and Engineering Seismology) in Pavia (Italy). The test

was conducted at half-scale and is part of a larger research initiative on mixed RC-URM wall

systems initiated at EPFL (École Polytechnique Fédérale de Lausanne). The key objective of

the testing campaign was to gain insights into the dynamic behaviour of mixed RC-URM

wall structures and to provide input for the definition of a performance-based design

approach of such mixed structural system.

Multiple shaking at increasing intensity was used to test the dynamic behaviour of the

examined building. The final shaking induced damage corresponding to the collapse

prevention limit state. Furthermore, random noise vibration tests were performed to monitor

the elongation of the natural periods induced by the damage progression.

The paper presents details on the structural system and the selected ground motion, the test

set-up and the instrumentation. Additionally, initial results of the shake table test are

presented with a first interpretation of the shown structural behaviour.


40

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF TORSIONALLY

IRREGULAR RC SHEAR WALL BUILDINGS WITH RUTHERMA BREAKERS

A. Yakut1, A. Le Maoult

2, B. Richard

2, F. Ragueneau

3, G.M. Atanasiu

4,

S. Scheer5, S. Diler

5

1Middle East Technical University, Turkey

2CEA/Saclay, France;

3ENS Cachan, LMT, France

4Technical University of Iasi, Romania

5SCHÖCK Company, Germany

Seismic response of reinforced concrete shear wall buildings with irregularities has not been

studied in detail and thus requires detailed experimental as well as numerical investigations.

Therefore, a challenging model building having irregularly placed shear walls in plan has

been designed and tested on the AZALEE shaking table at the TAMARIS laboratory in

CEA/Saclay. This research project, called ENISTAT, has been granted under SERIES

projects via Transnational Access to CEA/Saclay facility in France. The project has three

main objectives: 1) Study the behaviour of the mock-up under increasing bi-directional

horizontal synthetic earthquake records; 2) Attempt to evaluate the experimental results using

modern experimental techniques for data acquisition; 3) Implement & monitor performance

of a new structural element that allows for wall-slab connection to reduce the thermal energy

loss. The specimen has been designed professionally in conformity with Eurocode 8 and

constructed at EMSI Laboratory – CEA Saclay. Rutherma elements were used only at the

second floor level as a connection member between the shear walls and the slab. The model

building has been instrumented to get measurements of accelerations, displacements and

strains at various critical locations. To determine relative movement of the second floor slab

with respect to walls due to presence of Rutherma members, relative displacement readings in

the three principal directions were made at five different locations. Prior to testing, numerical

analyses have been carried out to determine the test sequence and application of ground

motion records. Five tests have been performed under a selected synthetic ground motion

record which is scaled to achieve different PGA levels. The ground motion records were

obtained artificially such that they conform with the design spectrum defined in Eurocode 8.

After initial low level tests, seismic tests having PGA‟s of 0.1g, 0.2 g, 0.4g, 0.6g and 0.8g

were applied consecutively. Before each tests low level white noise tests were performed to

determine frequencies of the mock-up. During the first three tests, i.e. up to 0.4 g, no

significant damage has been observed in the structural members except minor hairline cracks

on the spandrel beams. At 0.6g test, more cracks in beams were observed without any major

crack in walls. Strain measurements in Rutherma steel sections indicated that the strains were

within the elastic range. During the 0.8g test, separation of the shear wall member on the

flexible side from the foundation was observed. After the test, major cracks that are mainly

confined on that side in the first floor were observed. No damage on the Rutherma breakers

was observed.


41

ASSESSMENT OF THE SEISMIC RESPONSE OF CONCENTRICALLY-BRACED

STEEL FRAMES (TA PROJECT: BRACED)

B.M. Broderick1, A. Hunt

1, P. Mongabure

2, A. Le Maoult

2, J.M. Goggins

3, S. Salawdeh

3, G.

O‟Reilly3, D. Beg

4, P. Moze

4, F. Sinur

4, A.Y. Elghazouli

5, A. Plumier

6

1Trinity College Dublin, Ireland;

2CEA/Saclay, France;

3 NUI Galway, Ireland

4University of Ljubljana, Slovenia;

5Imperial College London, UK;

6University of Liege, Belgium

The seismic response of concentrically braced frames (CBFs) is affected by the reduced

ductility capacity of hollow section bracing members under low cycle fatigue conditions.

Seismic response assessment also needs to account for the role of the gusset-plate

connections commonly used in CBFs, which influence local ductility demand in the bracing

members. The SERIES TA project BRACED investigates this behaviour in full scale seismic

tests, the results of which are used to validate recently-developed models for the ductility

capacity of hollow section bracing members and recent proposals for the improved detailing

of gusset plate connections. The experimental and numerical studies identify active yield

mechanisms and failure modes in member/connection combinations and provide essential

data on the earthquake response of European CBFs.

The central element of the integrated experimental and numerical research programme is a

series of shake table experiments on full-scale model single-storey CBFs on the Azalee

shaking table at CEA Saclay. The model braced frame is 2955 mm high and 4900 mm wide

and carries a mass of 44 tonnes. The brace member and connection details are varied between

experiments to investigate a range of global and local member slenderness representative of

those found in European buildings. In each experiment, three separate tests are performed

with table excitations scaled to produce elastic response, brace buckling/yielding and brace

fracture. The experimental programme involving 12 independent experiments is supported by

correlative pre-test predictions and post-test simulations using pushover and time-history

analysis.

The experimental programme builds on a previous test programme completed under the

Ecoleader programme at NTUA Athens, but with the test models designed to evaluate the

ultimate earthquake response of CBFs with realistic brace members and connections. In

particular, the relative strengths of the brace members and gusset plate connections are varied

between experiments.

The principal outcomes of the test programme include measurements of the displacement

ductility capacity of the brace specimens; an evaluation of the influence of gusset plate

detailing on system ductility and frame stiffness; observations on the evolution of response

frequency with displacement amplitude; assessment of the contributions of brace and

connection yielding to overall inelastic deformation in CBFs; and measurements of

equivalent viscous damping in CBFs.

Session 6 – SERIES TA to Shaking Table Facilities on wood structures / Experimental Facilities

42

SERIES Transnational Access to Shaking Table

Facilities on wood structures / General on

experimental facilities

Session 6



43

SEISMIC PERFORMANCE OF LAMINATED WOOD FRAMES WITH MOMENT

CONNECTIONS UNDER SEISMIC LOADS:EXPERIMENTAL INVESTIGATION

B. Kasal1, A. Heiduschke

2, S. Pospisil

3, S. Urushadze

3, Z. Zembaty

4

1TU Braunschweig/Fraunhofer WKI, Germany

2 HESS Timber, LLC, Germany

3ITAM Prague, Czech Republic

4University Opole, Poland

Laminated wood frames (LWF) offer alternative solutions for mid-rise structures (defined

here as structures of up to about 8 floors high) traditionally built of reinforced concrete (RC)

or steel. The laminated wood can be manufactured to relatively large cross sections and

acceptable load capacities. Previous studies showed that laminated wood frames can resist

large seismic loads mainly due to their energy dissipation capacity (Heiduschke, A., B. Kasal,

and P. Haller 2009; Kasal, B., I. Pospisil, I. Jirovsky, M. Drdacky, A.Heiduschke, P. Haller

2004). The experiments, described in these papers also showed that the laminated wood

frames will undergo relatively large drifts, which under existing drift design limitations

represents a drawback that needs to be addressed either technically or in the code. While the

frames tested and reported in the above literature had nonlinear, dowel-bearing type

connections capable of moment transfer in one direction, they required bracing between the

bays and light decks were used to supply additional torsional stiffness. Such construction is

possible but limits the flexibility (bracing must be always present) and presents a design

challenges due to the large stiffness differences in two principal directions of the frame. This

paper describes the experimental program that studied the seismic behavior of three-story

LWB with spatial (3-dimensional) moment connections. The 3-D moment connections are

not common in wood structures due to difficulties in their design and manufacturing. The

connection between beams and columns is always facilitated through some kind of steel

hardware that must be effectively connected with wood. These connections cannot be

produced and designed as rigid due to the low dowel-bearing strength of wood and exhibit

typical stress-softening behavior that was studied for decades and large body of literature

exists to describe the behavior of joints under cyclic loads. It has been generally accepted that

results of slow cyclic load (about 0.5-1.0 Hz) can be used in subsequent prediction of a

timber joint behavior under more rapidly varying load (such as seismic event) although some

load rate dependency of a connection stiffness and capacity has been reported. In this work,

we have used slow cyclic load to evaluate the properties of 3-D moment connections and

used this information for design and construction of experimental frames loaded by a seismic

forces using shake tables. The methodology, instrumentation and main experimental results

of the research programs are presented.


44

INVESTIGATION OF SEISMIC PERFORMANCE OF MULTI-STOREY TIMBER

BUILDINGS (TA PROJECT: TIMBER BUILDINGS)

Maurizio Piazza1, Roberto Tomasi

1, Alfredo Campos Costa

2, Paulo Candeias

2

1University of Trento, Italy

2LNEC, Portugal

The paper describes the research activities for Transnational Access to Earthquake

Engineering Research Centre (NESDE) at LNEC (Laboratório Nacional de Engenharia Civil,

Lisboa, Portugal), within the framework of the SERIES Project. The aim is to verify, through

full-scale shaking table tests, the effects of earthquakes on some timber buildings

characterized by the same geometry (three stories houses, 7 m x 5 m in plan), designed

according to the state of the art of the timber engineering, but built through three different

timber systems: platform frame system (PF), log house system (LH), cross laminated system

(CLT). The project involves University of Trento, as Lead User of Transnational Access Use,

University of Minho and University of Graz, and different industrial partners. The specimens

have been accurately designed taking into account all the critical point of the different

construction systems (connection details, the presence of openings in walls and in floors, the

effect of non-structural elements etc.), and taking advantages of previous research

experiences of each of the team involved in the project. The LH and the two PF structures

were tested in May and June 2012, the CLT building was tested on February 2013.

The seismic behaviour of these typologies can be very different, being associated to many

factors such as the plane and elevation regularity, the type and the number of connection

systems etc. There are aspects so far not sufficiently investigated, such as:

- the deformability of the decks and walls (the relative stiffness significantly influences the

distribution of horizontal loads on the walls);

- the presence of openings in the panels; Standards, generally, only suggest empirical

factors in order to reduce resistance, or recommend not to consider as structural resisting

elements the panels containing openings;

- the influence of non-structural elements on the building behaviour.

At European level, there is still a lack of design provisions. Just as an example, the CLT and

LH construction systems in Eurocode 5 and Eurocode 8 have not specific design rules, while

regarding the structural material (such as the cross laminated panels in CLT system), due to

the absence of a specific technical Standard for the production, only specific technical

approvals must be considered.

The paper illustrates the assumptions, the facts and the present state of this on-going research

on earthquake resistant timber houses.


45

EXPERIMENTAL STUDY ON SEISMIC PERFORMANCES OF PRECAST

CONCRETE SHEAR WALL WITH JOINT CONNECTING BEAM

Xilin Lu1, Dun Wang

2, Bin Zhao

3

1Tongji University, Shanghai, China

Structural connection is the major feature of precast concrete shear wall distinguished from

monolithic shear wall and it plays an important role in seismic performances of precast

concrete shear wall. Different from widely used technologies such as mechanic sleeve

connection and sleeve-mortar splicing connection, joint connecting beam that is composed of

staggered splicing rectangular steel loops protruding from wall panel, assembly of

longitudinal steel bars and stirrups as well as concrete-casting is adopted as an alternative to

connect reinforcements of precast concrete shear wall. This paper is concerned with location

and height of the joint connecting beam on performances of slender precast concrete shear

wall with constant axial loading under quasi-static test and comparisons are made with that of

monolithic shear wall. The destruction of test specimen configuration, the top lateral loading-

displacement hysteretic curve, shear bearing capacity, deformation, energy dissipation

capacity, strength reduction, stiffness degradation, reinforcement strain, as well as concrete

strain were analyzed. Test results show that shear bearing capacity of precast concrete shear

wall with joint connecting beam is a little smaller than that of monolithic shear wall; the

failure mode, stiffness and the energy dissipation capacity of the precast shear wall specimen

are nearly the same or better than those of the monolithic shear wall specimen. It is indicated

that concept and detailing of the joint connecting beam is feasible and applicable to precast

concrete shear wall structure, which has the advantages of with no welding, no costly

mechanic sleeves and speeding up construction progress and application of precast concrete

structure. In the end, recommendations on the structural design are proposed for further

application of precast concrete shear wall with joint connecting beam.


46

FULL-SCALE PSEUDODYNAMIC TESTING OF THE SAFECAST

THREE-STOREY PRECAST CONCRETE BUILDING

Bournas D.1, Negro P.

2, Molina F-J.

2

1University of Nottingham, UK

2JRC, Italy

In the framework of the SAFECAST Project, a full-scale three-storey precast building was

subjected to a series of pseudodynamic (PsD) tests in the European Laboratory for Structural

Assessment (ELSA). The mock-up was constructed in such a way that four different

structural configurations could be investigated experimentally. Therefore, the behaviour of

various parameters like the types of mechanical connections (traditional as well as

innovative) and the presence or absence of shear walls along with the framed structure were

investigated. The first PsD tests were conducted on a dual frame-wall precast system, where

two precast shear wall units were connected to the mock up. The first test structure sustained

the maximum earthquake for which it had been designed with small horizontal deformations.

In the second layout, the shear walls were disconnected from the structure, to test the building

in its most typical configuration, namely with hinged beam-column connections by means of

dowel bars (shear connectors). This configuration was quite flexible and suffered large

deformations under the design level earthquake. An innovative connection system, embedded

in the precast elements, was then activated to create emulative beam-column connections in

the last two structural configurations. In particular, in the third layout the connectors were

restrained only at the top floor, whereas in the fourth layout the connection system was

activated in all beam-column joints. The PsD test results showed that, when activated at all

the floors, the proposed connection system is quite effective as a means of implementing dry

precast (quasi) emulative moment-resisting frames.


47

EXPERIMENTAL EARTHQUAKE ENGINEERING RESEARCH IN LNEC

CONTRIBUTION TO GLOBAL SEISMIC PERFORMANCE ASSESSMENT OF

STRUCTURES

E. Coelho, A. Campos Costa, P. Candeias, L. Mendes, A. Correia

Laboratório Nacional de Engenharia Civil (LNEC), Portugal

LNEC has a long experience in all fields of earthquake engineering and has been one of the

main European institutions developing research & technology activities in several topics of

this engineering science, such as seismic testing, structural monitoring, hazard analysis and

risk assessment, numerical modelling, development of codes and consultancy.

In the experimental field, LNEC holds a facility of excellence at European level for

earthquake engineering research. Apart from the incorporation of significant material

resources resulting from the dimension of the facility, an interdisciplinary team is responsible

for the assessment of experimental programs, integrating specialists in all fields of earthquake

engineering. This allows the use of more appropriate approaches in seismic testing within a

comprehensive framework for seismic performance assessment. The experimental facility

operates since 1996 and, due to its characteristics, has been from the beginning included in

the European group of large-scale facilities in earthquake engineering, within the “Training

and Mobility of Researchers programme” of the European commission (4th

FP), later

continued through European consortia for earthquake and dynamic experimental research

within “Improving Human Potential programme” (5th

FP). Presently the LNEC facility holds

one of the four largest European shake tables and integrates the strong European 23-

consortium SERIES, “Seismic engineering research infrastructures for European Synergies”

of the 7th

Framework Programme, as one of the European world class research

complementary infrastructures providing access to external research groups. Therefore, a

significant portion of the experimental work carried out at LNEC results from the fruitful

links established with European institutions.

Apart from European collaborations and the 16-year important European funding, several

studies with national funding have been developed at the LNEC experimental facility for

seismic testing, in collaboration with Portuguese research institutions. Additionally several

shake table tests have been performed in cooperation with the Portuguese industry, both to

study the adequacy of the seismic behaviour of specific types of precast reinforced concrete

construction systems for use in substations, and to investigate the behaviour of electrical and

mechanical equipment subjected to dynamic ground input motions.

LNEC has also been actively involved in the continued development and implementation of

experiments dealing with identification and dynamic characterization of structures, in the

framework of consultancy studies for the seismic assessment of existing structures. While

describing the significant legacy of LNEC in the fields of seismic testing and global seismic

performance approaches, particular relevance is given to the participation and main outcomes

of the SERIES‟ transnational access, networking and joint research activities. Finally, some

ambitious plans on future directions for seismic research and testing at LNEC are outlined.

Session 7 – Analytical & Experimental work on SSI, wave propagation and field testing

48

Analytical and Experimental work on soil structure

interaction, wave propagation and field testing

including SERIES Transnational Access to

Shaking Table Facilities

Session 7

Thursday, 30 May 2013


49

LARGE-SCALE LABORATORY EXPERIMENTS OF LANDSLIDE GENERATED

TSUNAMIS IN THE NEES TSUNAMI WAVE BASIN HALF A CENTURY AFTER

THE VAJONT DAM DISASTER

Hermann M. Fritz, Brian C. McFall, and Fahad Mohammed

Georgia Institute of Technology, USA

The 50th

anniversary of the Vajont disaster highlights an extreme landslide tsunami in a

narrowly confined reservoir behind a 265.5 m high double curved arch dam. A maximum

water depth of 250 m was reached by early September 1963 during the third filling attempt of

the reservoir, but as creeping on the southern flank increased a third reservoir draw down was

initiated. By October 9, 1963 the water depth was lowered to 240 m as the southern flank of

Vajont reservoir catastrophically collapsed on a length of more than 2 km. The lateral

spreading of the surge overtopped the dam crest and sent a flood wave into the Piave Valley

resulting in 2000 fatalities. The wave runup in direct prolongation of slide axis reached the

lowest houses of Casso 270 m above reservoir level before impact corresponding to the

second largest tsunami runup in recorded history behind only the 1958 Lituya Bay, Alaska

landslide tsunami with 524 m runup.

Landslide tsunami hazards exist even in areas not exposed to tectonic tsunamis. Source and

runup scenarios based on real world events are physically modeled in the three dimensional

tsunami wave basin (TWB) of the Network for Earthquake Engineering Simulation (NEES)

at Oregon State University (OSU). A novel pneumatic landslide tsunami generator (LTG)

was deployed to simulate landslides with varying geometry and kinematics. The LTG

consists of a sliding box filled with up to 1,350 kg of naturally rounded river gravel which is

accelerated by means of four pneumatic pistons down the 2H: 1V slope, launching the

granular landslide towards the water at velocities of up to 5 m/s. Topographical and

bathymetric features can greatly affect wave characteristics and runup heights. Landslide

tsunamis are studied in different topographic and bathymetric configurations: far field

propagation and runup, a narrow fjord and curved headland configurations, and a conical

island setting representing landslides off an island or a volcanic flank collapse. Water surface

elevations were measured using an array of resistance wave gauges. The granulate landslide

shape and front velocity were measured using above and underwater cameras. Three-

dimensional landslide surfaces with surface velocities were reconstruction using a stereo

particle image velocimetry (PIV) setup. The speckled pattern on the surface of the granular

landslide allows for cross-correlation based PIV analysis. Wave runup was measured with

resistance wave gauges along the slope and verified with video image processing. The

measured landslide and tsunami data serve to validate and advance 3-dimensional numerical

landslide tsunami and prediction models.


50

CAISSON FOUNDATIONS SUBJECTED TO SEISMIC FAULTING:

REDUCED-SCALE PHYSICAL MODELLING

I. Anastasopoulos, O. Zarzouras, T. Georgarakos, V. Drossos, and G. Gazetas

National Technical University of Athens, Greece

As part of the SERIES project, the Laboratory of Soil Mechanics of the National Technical

University of Athens conducted a series of physical model tests to investigate fault rupture

propagation through sand and its interaction with embedded caisson foundations. Besides

from being typical for bridge structures, the choice of embedded caisson foundations offers

the possibility of observing strongly nonlinear phenomena, such as the diversion and

bifurcation of the fault rupture path. A series of reduced-scale experiments were conducted,

investigating: (a) the style of dip-slip faulting (normal or reverse), and (b) the position of the

foundation relative to the fault rupture. The “bedrock” is subjected to movement due to fault

rupture of vertical offset h at a dip angle α = 45o. The displacements of the foundation, Δx,

Δz, and the rotation θ, as well as the deformation of the soil mass were recorded during the

experiments through image analysis and laser scanning of the soil surface. In the first case,

high-resolution digital cameras were utilized to capture images of the deformed soil during

the test, which were processed through image analysis software. In the latter case, a novel

technique was developed and applied through a custom system, designed and constructed in-

house. After each displacement increment, the ground surface was scanned with 8 laser

displacement transducers, travelling along the specimen at a constant speed, producing a

digital relief of the deformed surface. It is shown that the foundation acts as a kinematic

constraint, altering substantially fault rupture path. The horizontal and vertical movement and

the rotation of the caisson are a function of its position relative to the fault rupture.

Depending on the latter, a variety of interesting interaction mechanisms develop, such as

bifurcation of the rupture path and diffusion of plastic deformation. The conducted

experiments are in good qualitative agreement with similar centrifuge model tests, confirming

the validity of the experimental procedure, and enriching the experimental dataset on this

important research topic.


51

EFFECT OF SOIL STRUCTURE INTERACTION ON HIGHER MODES

PARTICIPATION

Seyed Abolfazl Mirfattah1, Seyed Kazem Mirfattah

2

1UME School, IUSS Pavia, Italy 2Azad University of Yazd, Iran

Higher modes effects have been usually a concern in designing structures against earthquake

actions since they can alter the internal forces and location of plastic hinges. On the other

hand soil structure interaction (SSI) affects the modal properties of the system. In this study

the effect of SSI on modal participation factor and modal properties of a simple multi degree

of freedom system is investigated. In order to simulate soil structure interaction a direct

method is used and a rigorous finite element model of soil half space is presented. The role of

SSI on amplification or attenuation of higher modes motions is examined. The results show a

dramatic change in the participation of higher modes due to soil, foundation and structure

interaction.


52

ESTIMATION OF SOIL STRUCTURE INTERACTION EFFECTS, CONSIDERING

THE FREQUENCY CONTENT OF THE MOTION

Seyed Hosein Mirfattah, Seyed Ali Mirfattah

JAHAD NASR Consultant Engineering Group, Yazd, Iran

In substructure method used in soil-structure interaction (SSI) analysis, interaction between

soil and foundation is modeled via spring and dashpot elements. Mechanical properties of

these elements depend on soil characteristics, foundation properties and also frequency of

motion. Therefore the response of the whole system is also frequency dependant. In this study

a number of structures are considered as simplified lumped mass SDOF systems and

equivalent spring and dashpot properties are calculated according to foundation impedance

by program DYNA. Circular foundations on soft soil (ground type D) are considered. Then

sensitivity of SSI effects on the response, to excitation frequencies in form of harmonic

motions and real ground motions are studied. Results show when the excitation frequency is

below a certain threshold, dramatic increase in maximum drift in short period systems and

considerable even in long period ones is observed this threshold is fundamental natural

frequency of the whole SSI system.


53

DEVELOPMENT OF NEW INFINITE ELEMENT FOR NUMERICAL

SIMULATION OF WAVE PROPAGATION IN SOIL MEDIA

Vlatko Sesov, Kemal Edip and Julijana Cvetanovska

IZIIS, University Ss. Cyril and Methodius, R. Macedonia

Numerical simulation of geo-dynamical problems such as propagation of waves in soil media

still pretends to be huge challenge for geotechnical research community. Modeling of soil

geometry as unbounded space have been subject of investigation by many researchers

[Bettess, 1980; Marques and Owen, 1984; Akiyoshi 1998; Pastor 1999]. In simulating

unbounded domains, infinite elements are very useful tool to describe the far field behavior,

whereas the near field is described through conventional finite elements. The spatial

discretization of the far domain is considered using the infinite elements.

This paper presents work that has been done on developing the new infinite element which

can be applied on saturated media subjected to dynamic loading. The basic idea consists of

mapping an infinite region into a finite one. This technique needs appropriate mapping

functions by which a domain, unbounded in one direction, is transformed into a bounded one.

These mapping functions are obtained as a product of standard shape functions for finite

direction and special mapping functions for the infinite direction. The simulation of wave

propagation into infinity is realized in the time domain. However, in dynamical applications,

some additional effects must be taken into account. In fact, when body waves approach the

interface between the FE and the IE domains, they partially reflect back to the near field as

the quasi-static infinite elements cannot capture the dynamic wave pattern in the far field. To

overcome this, the waves are absorbed by adding a layer of viscous damping which basically

belongs to the absorbing boundaries class. The idea of adding a layer of viscous damping

originates from the work by Lysmer and Kuhlemeyer [1969], in which velocity and

parameter dependent damping forces are introduced to get rid of artificial wave reflections.

Newly infinite element of five nodes has been developed and implemented in ANSYS, using

the user programmable features, UPF. An absorbing layer has been added to the infinite

element by considering the wave velocities in the damping matrix. The matrices

corresponding to the mapped infinite elements is very similar to the one used for the standard

finite elements. The only adjustment concerns the existence of mapping functions different

from the shape functions.

Results from performed analytical investigation on one dimensional wave propagation

problems using Heaviside step function and impulse functions and two dimensional wave

propagation in a circular quarter space emphasized some of the key issues regarding the soil

behavior during the wave propagation.


54

DESIGN AND CONSTRUCTION OF LAMINAR CONTAINER

FOR 1-G SHAKING TABLE TESTS

Vlatko Sesov, Julijana Cvetanovska, Kemal Edip and Zoran Rakicevic

IZIIS, University Ss. Cyril and Methodius, R. Macedonia

Investigation in the field of earthquake geotechnical engineering involve different

methodologies and approaches such as dynamic soil element tests, reduced scaled models,

numerical and analytical models and full scaled field tests. If done properly, scaled model

tests can be advantageous for seismic studies due to their ability to give more realistic

information about ground acceleration amplification, variation of pore pressures in the soil

medium, nonlinear behavior of soil, occurrence of failure, and soil structure interaction

phenomena.

This paper describes the process in design, fabrication and commissioning of a laminar shear

box for use in seismic geotechnical studies. A laminar box is a container which allows

„friction-free‟ horizontal movement of soil model and it is placed on a shaking table platform

to simulate wave propagation during earthquakes through a soil layer of finite thickness. The

laminar box described in this paper is built with dimensions 2 x 1 m (plan view) and 1.5 m in

height. It is designed to be used for shaking table tests on wide range of geotechnical

problems. The numerical analysis and preliminary calculations have been conducted to study

the performance of the laminar box in order to fulfill the design criteria are also taken into

consideration. Important aspects for the experimental setup of liquefaction studies,

characterization of investigated sand, model preparation, and soil properties are pointed out.

Special type of „contact-elements‟ are installed between laminar rings which significantly

improve the free deformability of ground model subjected to seismic loading. Amplification,

liquefaction and cyclic mobility phenomenon, excess pore water pressure generation and

dissipation rates, and further soil-structure interaction investigations can be performed using

such experimental tool. Intensive shaking table testing at the Geotechnical Laboratory in

IZIIS are performing in order to verify the technical characteristics of the laminar box. The

construction of such laminar box is expected to improve the research capabilities of European

research area (ERA) in the field of earthquake geotechnical engineering.


55

ANALYSIS OF THE DYNAMIC BEHAVIOR OF SQUAT SILOS CONTAINING

GRAIN-LIKE MATERIAL SUBJECTED TO SHAKING TABLE TESTS

Dora Foti1, Salvador Ivorra

2, Tomaso Trombetti

3, Stefano Silvestri

3, Giada Gasparini

3

1Technical University of Bari (Italy)

2University of Alicante (Spain) 3University of Bologna (Italy)

This paper reports the outcomes of a series of shaking table tests performed at EQUALS lab

of Bristol University in the framework of SERIES project. The experimental test campaign

was devoted to the evaluation of the effective behaviour of grain in flat-bottom silos full of

grain during an earthquake. This research work starts from all the same basic assumptions of

Eurocode 8 except for the one regarding the horizontal shear forces among consecutive

grains. Only this difference leads to a new physically-based evaluation of the effective mass

of the grain, which horizontally pushes on the silo walls. The analyses are developed by

simulating the earthquake ground motion with time constant vertical and horizontal

accelerations and are carried out by means of simple dynamic equilibrium equations that take

into consideration the specific mutual actions developing in the ensiled grain. The findings

indicate that, in case of squat silos (characterized by low, but usual, height/diameter

slenderness ratios), the portion of the grain mass that interacts with the silo walls turns out to

be noticeably lower than the total mass of the grain in the silo and the effective mass adopted

by Eurocode 8.

Two series of tests have been performed with two different heights of the ensiled material to

simulate a silo more or less squat silo. The ensiled material has been modeled with ballotini

glass. In the paper, the silo model for the first and second test is presented, and then the

dynamic behavior of the structure is described with reference to the two series of shaking

table tests. The results indicate that, in the case of squat silos the portion of grain mass that

interacts with the silo walls turns out to be noticeably lower than the total mass of the grain in

the silo.


56

STUDY OF MULTI-BUILDING INTERACTIONS AND SITE-CITY EFFECT

THROUGH AN IDEALIZED EXPERIMENTAL MODEL

Logan Schwan1, Claude Boutin

1, Matt Dietz

2, Luis A. Padron

3, Pierre-Yves Bard

4, Silvia

Castellaro5, Erdin Ibraim

2, Orlando Maeso

3, Juan J. Aznárez

3, Colin Taylor

2

1University of Lyon, France;


3Universidad de Las Palmas de Gran Canaria, Spain

4ISTerre / IFSTTAR, University of Grenoble, France

5University of Bologna, Italy

Seismic risk may be a strong concern for cities as they concentrate population, real estate

and/or strategic public services. The common earthquake engineering practice does usually

consider the substratum, but disregards the resonant „surstratum‟ made up by the city itself.

However numerical and analytical models suggest that global soil-structure interactions, i.e.

Site-City effect, can occur and be significant, especially when the fundamental frequencies of

the soil and of the heaviest buildings coincide.

The aim of the present SERIES-SMISCE study is to investigate experimentally this

phenomenon and to compare the resulting data with two models. In the theoretical model

derived by homogenization [Boutin et al. (2006)], the city is shown to act as a frequency-

dependent analytical surface impedance. The numerical model consists in a 2D, hybrid BEM-

FEM approach that describes the layer by boundary elements and the structures by finite

elements. Experimentally, the site-city interaction is studied through an idealized specimen.

A polyurethane foam block with metric dimensions stands for the soil layer and 37 parallel

vertical aluminium sheets stand for the buildings. The buildings can bend and resonate with

out-of-plane excitation, but remain quasi-static with in-plane excitation. It enables to point

out the differences between resonant and inert masses. The specimen is designed to provide a

good matching between the fundamental frequencies of the foam block and of the aluminium

resonators. The whole is attached to the shaking table of Earthquake and Large Structures

Laboratory (EQUALS), and excited with a series of signals.

While excited in the non-resonant direction, the system acts classically as a layer with added

inert mass on the top surface. While excited in the resonant direction, global interactions (i)

split the resonance peak into two peaks that favours beatings; (ii) reduce significantly both

surface and the resonators‟ motions at their common fundamental frequency; (iii) decrease

the amplitude of the resonance peaks; (iv) induce longer signals with slower decreasing

codas. Another unconventional phenomenon is a depolarization effect. These specific

features have been recovered by both analytical and numerical models giving (i) a qualitative

and quantitative agreement with experimental results and (ii) a quasi-perfect agreement with

one another.


57

EUROPROTEAS: A FULL-SCALE EXPERIMENTAL FACILITY FOR

SOIL-FOUNDATION-STRUCTURE INTERACTION STUDIES

Dimitris Pitilakis1, Emmanuil Rovithis

2, Anastasios Anastasiadis

1,

Kyriazis Pitilakis1

1Aristotle University Thessaloniki

2Institute of Engineering Seismology & Earthquake Engineering (ITSAK), Greece

We present the experimental campaign to study soil-foundation-structure interaction and

wave propagation in soil media due to structural oscillation that took place in the

experimental facility of Euroseistest in Greece. The tests series were performed in the

framework of the on-going European project “Seismic Engineering Research Infrastructures

for European Synergies, SERIES” by means of a real-scale simplified model structure, called

EuroProteas, built in Euroseistest site. A particularly stiff structure founded on soft soil was

designed to mobilize soil-foundation-structure interaction effects. The structure‟s outer

dimensions are 3x3x5m having reconfigurable mass and stiffness properties. Two distinct

reinforced concrete slabs of 9t mass each form the superstructure mass, whereas a similar

R/C slab is employed as the surface foundation of the structure. Superstructure loads are

transferred to the foundation soil though four steel columns, interconnected in all four sides

with removable steel bracing system. Provisions for mounting an eccentric mass vibrator

were made on both the foundation and the roof slab. Provisions were also made for pull-out

experiments by a wire rope securely connected to the roof slab. Two boreholes (one at the

geometrical center of the surface foundation slab and one at 0.5m away from the foundation

side) and two trenches in two perpendicular directions allow for dense instrumentation for the

response recording.

In the framework of SERIES, six experimental campaigns took place: three pull-out (free-

vibration) and three forced-vibration sets of tests. Pull-out was performed with a 1t

counterweight and the total pull-out force exceeded 15kN. Forced-vibration tests were

performed using an eccentric mass vibrator, with sine sweeps in the range between 1Hz and

10Hz, and total force exceeding 20kN. The vibrator was placed both on the foundation and

the top of the structure.

Soil and structural response under free and forced vibration was recorded in a dense 3D array

of more than 60 recording devices (accelerometers, seismometers, shape acceleration arrays).

Instrumentation in the soil covered a volume of 9x9x12m around and beneath the foundation.

In this paper we present the recorded response from selected tests, highlighting soil-

foundation-structure effects in the structure and in the soil. We also present some preliminary

comparisons between the recorded response and numerical 2D and 3D simulations of the

experiments.

Session 8 – Analytical & Experimental Techniques / SERIES TA to Reaction Wall Facility

58

Analytical and Experimental Techniques / SERIES

Transnational Access to Reaction Wall Facility

Session 8

Thursday, 30 May 2013


59

IN-SITU SEISMIC PERFORMANCE TESTS OF A SCOURED BRIDGE

Kuo-Chun CHANG

National Center for Research on Earthquake Engineering, Taiwan

This paper presents a series of in-situ seismic performance tests of a bridge before its

demolition due to accumulated souring-induced problem. The tested bridge has two identical

parallel lanes, while right lane was constructed in 1961 with pier walls, and left lane in 1995

with circular columns, respectively. Each lane consists of seven 38 m-long simply-supported

PC I-girders. The experiment program includes three cyclical loading tests and one pseudo-

dynamic test. As a strong reaction wall system, the pier wall and two supplemental steel A-

shape frames were integrated to employ two hydraulic oil jacks, so as to apply lateral force

on the column and push column to the target displacements. The column is 180cm in

diameter and 1030cm in height, reinforced with 30-D32 longitudinal reinforcing bars and

transversely reinforced with D16 perimeter hoops spaced 20 cm apart. P3 column represents

a benchmark specimen with no scouring, while P4 is exposed up to 33 percent of the length

of the caisson foundation. Similar to P3 fixed on the ground, P2 is subjected to a code-

compatible ground acceleration of 0.32g first and then followed by a pushover test. Though

given two different exposed length of caisson foundation, it is due to gravel material of

ground, which is similar to a fixed-base condition, that each column behaved ductile and

achieved maximum lateral force of 1000kN at 5% drift ratio with buckling of longitudinal

reinforcements and separation of lateral reinforcements. However, the axial load verified by

the system identification showed a relative small value about 0.05 f'cAg, as a result to explain

why the failure of bridge column was flexural-dominate, even the design details didn't

satisfied with the current seismic design detail requirements.


60

VALIDATION OF A VISUAL DEFORMATION MEASUREMENT SYSTEM

Binbir E., Demir C., Ispir M., Ilki A.

Istanbul Technical University, Turkey

The pilot studies on visual deformation measurement systems at Structural and Earthquake

Engineering Laboratory of Istanbul Technical University (ITU) dates back to 2002. At that

time visual measurements were made with the support of geomatics department of Civil

Engineering Faculty of ITU.

Usage of conventional measuring devices to obtain deformations has some drawbacks such

as; a) deformations over a small part of test specimen can be measured, b) installation of

measuring devices may take notable time, c) during the installation of the devices, specimens

can be damaged due to various attachments, d) for data acquisition, a data logger is generally

required, e) the measurement devices may be out of order during the test, due to the excessive

damage of the specimen, f) due to the nature of the applied load and/or the characteristics of

specimens, the specimen can fail suddenly causing damage of the measurement devices.

Considering these drawbacks, a visual deformation measurement system is developed at the

Structural and Earthquake Engineering Laboratory of ITU within Series Project. The visual

measurement system consists of hardware and software components. Hardware components

include high-resolution camera, lens, metric calibration plate, and I/O card (USB). Software

component includes a graphic interface for measurement preparation and related modules and

measurement/reporting modules. The capability of the visual system is limited from several

aspects. The displacements can be tracked in 2D. The system is calibrated for two camera-to-

specimen distances (1.5 and 2.5 m) and operates with a precision less than 0.1 mm.

In order to validate the displacement measurements of the visual system, the measurements

obtained using this system are compared with the measurements of the conventional

displacement transducers. The validation study is conducted using the deformation data

obtained from the tests of the short columns confined with FRP sheets. This comparison

showed that the visual system measurements are in good agreement with the conventional

measurements.


61

DEVELOPMENT OF WIRELESS SENSORS FOR SHAKE TABLE AND FULL

SCALE TESTING AND HEALTH MONITORING OF STRUCTURES

Zoran T. Rakicevic, Igor Markovski, Dejan Filipovski, Slobodan Micajkov,

Mihail Garevski

IZIIS-SS “Cyril and Methodius” University, R. Macedonia

The application of wireless technology to testing and monitoring of civil structures has been

gaining considerable interest over the past decade or two.

Wireless sensors are not sensors by themselves, but rather are autonomous data acquisition

nodes to which traditional structural sensors (e.g. accelerometers) can be attached. Wireless

sensors are best viewed as a platform in which mobile computing and wireless

communication elements converge with the sensing transducer. With wireless sensors rapidly

evolving in multiple engineering disciplines, there currently exist a large number of different

academic and commercial wireless sensor platforms.

At IZIIS, within the framework of the SERIES project, two types of wireless sensors have

been developed. The first one MIMRACS (Micro Integrated Measuring, Recording And

Communication System) sensor presents an intelligent self-controlled high integrated

GPS/GPRS/WEB based micro processing digital 3D measurement device, with a possibility

for power independence appropriate for measuring, storing and transferring data with an

exact time of their appearance.

given. It has 3 MEMS Model 3028 piezoresistive accelerometers, one for each orthogonal

axis, microprocessor, 24-bit A/D converter, programmable amplifiers, programmable trigger

(x+y+z), inclinometer, gyroscope, GPS/GPRS/GSM modules, Flash memory, USB

communication and power supply.

The other type is developed on the similar platform as MIMRACS, with a difference that it is

more compact and lighter, has one MEMS Model 3028 piezoresistive accelerometer and uses

a ZigBee module and protocol for wireless communication.

Both developed sensors are suitable for laboratory testing (shake table testing) and full scale

measurements (ambient and force vibration) of structures, as well as health monitoring of

structures. The MIMRACS sensor can, also, be used as standalone seismic station in a

network for monitoring and recording of strong motion data.

Both sensors have been tested in laboratory condition by shake table - standalone testing and

testing on models, while recorded signals are compared to traditional wired accelerometers.

The comparison results showed very good correlation.

In this paper, both developed wireless sensors will be presented in detail, their hardware and

software, as well as comparison results from various conducted tests.

A short review of the world‟s wireless sensor development will also be given.


62

RECENT ADVANCES IN SEISMIC DESIGN OF RC TALL BUILDINGS USING

ULTRA-HIGH-STRENGTH MATERIALS IN TAIWAN

Shyh-Jiann Hwang

National Taiwan University

Metropolis renewal is an urgent need for Taiwan due to its high population density in urban

areas. Constructing the high-rise residential buildings has become a necessity for urban

renewal. The use of ultra-high-strength materials for the high-rise RC buildings can provide a

rational solution for this demand. However, the seismic attacks do pose a serious thread for

these high-rise RC buildings. Japan had launched the New RC Project since 1988. Recently, a

59-story RC building had been successfully constructed in Japan. This clearly indicates that

Japan had established a good technology of the high-rise RC buildings for Taiwan to follow

and to start its own. Since 2008, Taiwan started its research programs on the seismic design

of RC buildings using ultra-high-strength materials. This speech reviews existing research on

RC structures using ultra-high-strength materials in Taiwan to identify findings that may be

immediately useful to the structural engineers in government and private practice who are

working on high-rise RC building.


63

REFINED AND SIMPLIFIED NUMERICAL MODELS OF AN ISOLATED OLD

HIGHWAY BRIDGE FOR PSD TESTS

F.Paolacci1, S.Alessandri

1, A. Mohamad

1, D. Corritore

1, R. Derisi

2

1University Roma Tre, Rome, Italy

2University of Naples, Naples, Italy

RETRO project aims at studying the seismic behaviour of existing R.C. bridges and the

effectiveness of innovative retrofitting systems. The research program focuses on old bridges,

not properly designed for seismic action. In particular the seismic vulnerability of an old-

Italian viaduct with portal frame piers will be evaluated. A proper isolation system will be

designed using Slide Spherical Bearings. On the basis of a previous experimental campaign

consisted of cyclically imposed displacements on 1:4 reduced scale models of a reinforced

concrete portal frame pier, belonging to a typical old highway viaduct, a new experimental

activity has been proposed.

In particular, two specimens (scale 1:2.5), 2-floors and 3-floors one-bay reinforced concrete

frame respectively, will be realized and tested using the PsD technique with sub-structuring,

including the modeling of the entire viaduct. During the test, different configurations will be

considered including retrofitted viaduct using Spherical Sliding Bearings and “as-built”

viaduct.

The aim of the proposed experimental activity is: (i) Increasing the knowledge on the non-

linear behaviour of portal frame piers in presence of plain steel bars on which few studies are

realized; (ii) Employment of large-scale experimental test for the seismic assessment of

existing bridges; (iii) Study of the effectiveness of traditional and innovative seismic isolation

systems (FP isolators).

In this paper the non-linear response of the viaduct in “as-built” and “isolated” configurations

are analyzed through a non-linear model developed using the "NL platform OpenSees". The

response of a refined model that takes into account the main non-linear phenomena of the

viaduct (strain penetration of plain bars, shear deformation of transverse beams, flexural

deformations of columns and beams) is analyzed. The aim of the simulations is to evaluate

the seismic response of the entire bridges. In addition the effectiveness of the adopted

isolation systems is analyzed and discussed. The results are used to simulate the seismic

response of the viaduct in the isolated configuration.

The response is carried out using two accelerograms, as in PsD test campaign. Two signals

recorded during the Emilia earthquake in 2012 have been adopted; one for slight damage

condition and the other for Ultimate limit state condition. Because of the complexity of the

refined model, a simplified model is also proposed. It is composed of an elastic beam (the

deck) connected to non-linear springs, which are calibrated using the non-linear cyclic

response of each pier. A comparison between refined and simplified models is shown and

some conclusions on the usability of the simplified one are carried out.


64

FULL-SCALE EXPERIMENTAL VALIDATION OF DUAL ECCENTRICALLY

BRACED FRAME WITH REMOVABLE LINKS

(TA PROJECT: DUAREM)

Aurel Stratan1, Dan Dubina

1, Adriana Ioan

1, Fabio Taucer

2, Martin Poljansek

2

1“Politehnica” University of Timisoara, Romania

2JRC, Italy

Conventional seismic design philosophy is based on dissipative structural response, which

implicitly accepts damage of the structure under the design earthquake and leads to

significant economic losses. Repair of the structure is often impeded by the permanent

(residual) drifts of the structure. The repair costs and downtime of a structure hit by an

earthquake can be significantly reduced by adopting removable dissipative members and

providing the structure with re-centring capability. These two concepts were implemented in

a dual structure, obtained by combining steel eccentrically braced frames (with removable

bolted links) and moment resisting frames. The bolted links provide the energy dissipation

capacity and are easily replaceable, while the more flexible moment resisting frames provide

the necessary re-centring capability. The solution will be validated by full-scale pseudo-

dynamic test of a three-storey model of a steel structure with re-centring capability at the

European Laboratory for Structural Assessment (ELSA) at the Joint Research Centre in Ispra

within the framework of Transnational Access of the SERIES Project financed by the

European Commission.

The general set-up of the experimental mock-up, instrumentation, and the test sequence are

described. Pre-test numerical simulations were performed in order to assess the response of

the structure under different levels of the seismic input, as well as to establish the optimal

sequence of link removal and replacement. Moreover, due to concerns about the safety of

link removal through oxy-fuel cutting as results of sudden release of forces, a set of dampers

was installed with a temporary bracing system. Numerical simulations were used to provide

the optimal damper properties that would prevent vibrations in the worst scenario of sudden

release of forces during link removal.

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³(DUWKTXDNH(QJLQHHULQJ5HVHDUFK Joint with …...Schwan L, Boutin C, Dietz M, Padron LA, Bard PY, Castellaro S, Ibraim E, Maeso O, Aznárez JJ, Taylor C 56 EuroProteas: A full-scale