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Evaluation of structural response
under exceptional seismic actions
Matej Fischinger1, Gaetano Della Corte2
1 Faculty of Civil and Geodetic Engineering
University of Ljubljana
2 Department of Structural Engineering
University of Naples “Federico II”
Urban Habitat Constructions under Catastrophic Events
Naples, Italy,16-18 September 2010
Extreme conditions occur when both loading and structural resistance are combined in such a way to reduce the safety level below acceptable values.
This situation may arise either when the loading is larger than expected (foreseen by the codes existing at the time of the design of the structure) or when the provided capacity was lower than anticipated by the modern standards.
Exceptional seismic actions
Research on structural response under exceptional seismic events
To support the development of the PBD procedures
As a basis for the seismic risk studies
To gain information about innovative structural systems
To provide data for seismic rehabilitation of the systems
designed prior to the development of modern seismic
design principles
To enhance the ability of structures to withstand impact
and explosion loads
Overview
State of the art
Contributions from COST members
Experimental studies – through collapse
Analytical studies
RC structures
Steel structures
Masonry structures
RC structures - Precast structures (contribution from COST members)
PRECAST project (Fischinger et al. 2008,
Toniolo 2007 )
Large rotations of columns (up to 10%)
Ibarra’s model (2005) was modified at UL
Modified Ibarra model
RC structures – Precast structures
(contribution from COST members)
Risk studies on RC precast structures with
strong connections (Fischinger at al. 2008) –
PEER methodology
Other vulnerability studies on RC structures
Kappos (2007)
RC structures - Precast structures (contribution from COST members)
How the connections behave in such
conditions?
SAFECAST project - Response of connections
at large rotations of columns
Experiments on dowel connections (COST26 final
conference – Fischinger et al.) – large rotations
RC structures – Walls
(contributions from COST members)
Seismic response of
lightly reinforced
walls - Fischinger et
al. 2008
Pushover
investigation of 3D
wall systems with
flexible foundation
using capacity
spectrum method –
Apostolska et al.,
2008
Blind prediction of the response of 7-story wall, tested at UCSD
MVLEM
RC structures(contributions from COST members)
Experimental investigation of existing RC
buildings sesimically upgraded by means of
several innovative techniques (e.g. FRP,
eccentric braces and buckling restrained braces)
- Mazzolani et al., 2007
Controventi
con leghe a
memoria di
forma
Materiali
Compositi(C-FRP)
Controventi
Eccentrici(EB)
Controventi
ad instabilità impedita
(BRB)
Isolamento con
isolatori in gomma
(BI)
Prova di spinta sulla
struttura in c.a.
Pannelli
a taglio
(SSP)
5 64321
RC structures(contributions from COST members)
Full scale experimental tests on a real masonry-
infilled reinforced concrete two story frame
building- Mazzolani et al., 2007
RC structures(contributions from COST members)
Modelling of upgraded RC structures (non-
ductile mechanisms of the original structure as
well as response of strengthen structure):
Mazzoalni et al., 2007: advanced model for RC in
real masonry infilled building
Bordea et al., 2007: modelling of enhacement of
ductility of RC columns strengthen by FRP
Landolfo et al. 2008: Experimental and analytical studies of typical European steel beams up to severe strength degradation
Strength and stiffness degradation was measured in the range of large plastic rotation demand
Empirical formulas for characterization of ductility and plastic overstrength were proposed
Steel structures
(contributions from COST members)
D’Aniello et al. 2008: Tests on buckling restrained braces subjected to large displacements that far exceed the design values
Design alternatives were proposed to maximize the brace capacity under the extremly large deformations.
Steel structures(contributions from COST members)
Stratan and Dubina 2008: Nearly full scale tests of eccentricaly braced bare steel frames with removable steel shear links
An appropriate detailing of end connections essential for good performance
Steel structures(contributions from COST members)
Landolfo et al. 2006, Della Corte et al. 2006, Dubina et al. 2007: Incremental dynamic analysis of different types of steel structures to investigate near-collapse response
Dogariu et al. 2007: Test on masonry pannels under monotonic and cyclic load
Results can be used as the baseline to evaluate the effectiveness of the retrofiting interventions
Informations can be used for development of the analytical model suitable for analysis of masonry shear pannels up to complete failure
Masonry structures(contributions from COST members)
Krstevska et al. 2007: Large scale test of historical mosque with a minaret
Test on the original bare masonry model, with a small intensity earthquake to produce small, repairable, damage
Tests on the repaired and strengthened model, until collapse of the minaret
Tests on the strengthened mosque until collapse. The strengthening systems were based on FRP materials
Masonry structures(contributions from COST members)
Masonry structures(contributions from COST members)
Two FEM numerical models of the original and strengthen structure
FEM models successfully used for the comparison of two structuresCalibration with large-scale model steel needed
De Matteis et al. 2008: Experimental and analytical investigations of the cental part of Fossanova gothich church
tests on the bare masonry, to produce moderate, repairable, damage; 2) tests on the strengthened model (transverse FRP rods) , until severe damage (close to the collapse)
Original structure PGA =0,14g, strengthen structure 0.4g
Masonry structures(contributions from COST members)
Until a decade ago very few experimental and analytical studies of the structural behaviour up to the collapse. Recently the interest has shifted towards near-collapse behaviour.
Impressive (full-scale) experiments were performed near to the collapse providing suitable data for the development of the adequate analytical models.
Conclusions and recommendations (1)
Empirical calibrated macro-models are prevailing. Although rather simple in concept they provide goodphysical understanding and consequently goodcontrol of the highly complex near-collapse mechanisms. Works performed within the COST C26 action have considerably contributed to these results.
Since each collapse mechanism of a particular structural element or structural system is so specific, general solutions are not to be expected. Long term solution is to perform sufficient experiments
Conclusions and recommendations (2)