Seismic Retrofit of Bridges “ EP – Estradas de Portugal” Experience Tiago Rodrigues, Estradas...

Seismic Retrofit of Bridges“EP – Estradas de Portugal” Experience

Tiago Rodrigues, Estradas de Portugal

Workshop DynamicPerformance, Assessment & Rehabilitation of StructuresMonte da Caparica | FCT-UNL – 31st October 2014

The Company

EP – Estradas de Portugal, SA is the general concessionaire of the Portuguese Road Network, whose mission is funding, maintenance, operation, rehabilitation and widening of the roads that are part of the National Network.

Within the structures that integrate the network, consists in ensuring:

- Safety conditions;

- Appropriate service levels;

- Proper lifecycle management.

Bridge Maintenance Management SystemEP as implemented a Bridge Conservation Management System that allows a vast

knowledge of bridges Condition Rating through a periodic update of the set of activities that

support the system. The system database shows more than 5.000 bridges surveyed in EP’s

direct management (or direct interference in their roads).

Assumptions for Seismic RetrofittingThe Bridge Conservation Management System allows prioritization of interventions depending on the severity of the anomalies in each structure.

Intervention is necessary

Structural AssessmentSeismic Retrofit

Assessment

Cost/Benefit analysis of the seismic retrofit

Partial Retrofit Total Retrofit Replacement

Seismic Retrofitting Methodology

In the vast majority of interventions taken by EP the need for seismic strengthening is due to the fact that the structures were designed based on previous building codes (design value of seismic action below the current one).

Main assumptions of structural reinforcement for seismic action:

- Increase of load capacity;

- Increase of ductility;

- Reduction of the action effects:

- Base isolation systems;

- Energy dissipation systems.

Case Histories

Santa Margarida do Sado Bridge

VNMilfontes BridgeNS Guia Bridge

Eng.º Jorge Moreira BridgeCoroa Bridge

Santa Margarida do Sado Bridge

Overview

• Roadway - E.N. 259

• Location – Grândola

• Construction – 1938

• Overall length - 100m

• Spans – 2 (50m each)

• Deck overall width – 8.40m

• Designer – Eng.º Ferrugento

Gonçalves (JAE)

Santa Margarida do Sado Bridge

Structural Solution

Superstructure of metallic simply-

supported spans

Concrete deck supported by

metallic transverse floor beams

and stringers

Pier and abutments

made of limestone

masonry

Two Pratt truss made by

composite profiles performed with

riveted steel plates

Santa Margarida do Sado Bridge

Structural Assessment Conclusions

• Central pier and foundation – Low bearing capacity for seismic design action;

Since the central pier strengthening would involve significant and expensive work and given the predictable construction of a new highway near the existing bridge, it was reconsidered its implementation, having been assessed rather a more simple and economical intervention that also improved the seismic behavior of the structure.

Santa Margarida do Sado Bridge

Seismic retrofitting solutions

• Introduction of elastomeric laminated stops in the abutments:

- In order to limit the longitudinal

displacement of the deck due to

seismic action, it were introduced

elastomeric laminated stops

between the lower chords of the

primary beams and the wall of the

abutments;

Santa Margarida do Sado Bridge

Seismic retrofitting solutions

• Strenghthening of the central pier stirrup:

- The reinforcement of the central pier

consisted in the execution of a concrete

ribbon in the stirrup to absorb and

transmit evenly to the pier the horizontal

forces associated with seismic action

transmitted by the bearings.

Santa Margarida do Sado Bridge

Venture Data

Contract Value 620.183,47 €

Seismic Retrofit Works 35.956,65 € (6%)

Designer:A2P CONSULT – Estudos e Projectos, Lda.

Contractor:TECNOVIA – Sociedade de Empreitadas, S.A.

Case Histories

Santa Margarida do Sado Bridge VNMilfontes BridgeNS Guia Bridge

Eng.º Jorge Moreira BridgeCoroa Bridge

NS Guia Bridge

Overview

• Roadway - E.N. 201

• Location – Ponte de Lima

• Construction – 1980

• Overall length - 250 m

• Spans – 5

• Deck overall width – 12.60m

• Designer – Prof. Correia de Araújo

NS Guia Bridge

Structural Solution

• Pre-stressed reinforced concrete deck, with three central spans of 58m and two external spans of 38m;

• Two-cell box girder deck with variable height from a minimum of 1.45m at the abutments and mid-span to a maximum of 2.90m on the piers;

• Has the particularity of being one of the first bridges to be built by the balanced cantilever method in Portugal;

NS Guia Bridge

Structural Solution

• The piers are of solid section, having reinforcement only on the outer skin with 0.20m thickness;

• The abutments consist of large reinforced concrete retaining walls;

• Given the characteristics of weak soil foundation, piers and abutments are founded in reinforced concrete deep strip foundations;

NS Guia Bridge

Structural Assessment Conclusions

• Piers – Shear ULS was not verified for seismic design action;

• Deep strip foundation – Bending and Shear ULS was not verified for seismic design action;

• Bearings – In the piers could not afford the displacements imposed by seismic action;

NS Guia Bridge

Seismic retrofitting solutions

• Oleodynamic devices:

- Installation of oleodynamic devices in one of the abutments, in order to transfer

part of the horizontal load of the piers and foundations for the abutments;

NS Guia Bridge

Seismic retrofitting solutions

• Abutments intervention:

- Execution of a resistant structure in the back of the right abutment

consisting of six piles 1.20m, able to support the horizontal loads

transmitted by the oleodynamic devices;

NS Guia Bridge

Seismic retrofitting solutions

• Introduction of lateral stops:

- Execution of reinforced concrete lateral stops in piers;

NS Guia Bridge

Venture Data

Contract Value 1.290.000,01 €

Seismic Retrofit Works 185.412,96 € (15%)

Designer:BETAR - Consultores, Lda.

Contractor:OBRECOL – Obras e Construções, S.A.

Case Histories

Santa Margarida do Sado Bridge VNMilfontes BridgeNS Guia Bridge

Eng.º Jorge Moreira BridgeCoroa Bridge

Vila Nova de Milfontes Bridge

Overview

• Roadway - E.R. 393

• Location – Odemira

• Construction – 1978

• Overall lenght - 363m

• Spans – 11

• Deck overall width - 16m

• Designer – Eng.º Lobo Fialho

Vila Nova de Milfontes Bridge

Structural Solution

• Pre-stressed reinforced concrete deck, with four central spans of 42m, five middle spans of 26m and two external spans of 32.5m;

• The external spans are continuous sections, cast-in-situ, supported by piers in cantilever upper beam and abutments of gravity type;

Vila Nova de Milfontes Bridge

Structural Solution

• The central spans are formed by continuous deck sections cast-in-situ, with 17m between supports, with cantilevers of 12.5m balancing out of the bifurcated ends of the piers, that receive the simply-supported spans;

Vila Nova de Milfontes Bridge

Structural Solution

• The simply-supported spans were executed in a second stage with precast beams united in the upper flanges through a cast-in-situ slab.

Vila Nova de Milfontes Bridge

Structural Solution

• The deck lays on four bifurcated hollow piers “V” shape, built in the riverbed and cast-in-situ;

• These piers lay on concrete shallow foundations and are founded on piles (P2 and P4) or deep strip foundations (P3), except P5 that as been founded directly on rock.

Vila Nova de Milfontes Bridge

Structural Assessment Conclusions

• High horizontal deformability of the isolated spans, with the possibility of falling;

The poor bearing capacity of foundations presented very high technical difficulties and disproportionate finantial burden, so if it was not feasible within reasonable parameters provide the structure an appropriate behavior facing seismic design action, it was minimized the risk of the bridge partial collapse.

• Foundations with insufficient resistance in particular to shear stress;

• Influence of the adjoining ground in the bearing capacity of the piles/deep strip foundations located in the riverbed;

Vila Nova de Milfontes Bridge

Seismic retrofitting solutions

• Impact control devices - dumpers:

- Creation of a horizontal forces

dumper sytem, with the placement

of viscous dampers that minimize

the problem of sudden impact in the

bond between the external spans

and the abutments by the shock

effect betwen the various modules

of the deck, also transmitting less

forces to the abutments.

Vila Nova de Milfontes Bridge

Seismic retrofitting solutions

- Introduction of longitudinal movement control system of the independent

spans which minimize the risk of failure for lack of support.

• Longitudinal displacements control system of independent spans:

Vila Nova de Milfontes Bridge

Venture Data

Contract Value 1.397.529,42 €

Seismic Retrofit Works 333.626,55 € (24%)

Designer:A2P CONSULT – Estudos e Projectos, Lda.

Contractor:OBRECOL – Obras e Construções, S.A.

Case Histories

Santa Margarida do Sado Bridge VNMilfontes BridgeNS Guia Bridge

Eng.º Jorge Moreira BridgeCoroa Bridge

Coroa Bridge

Overview

• Roadway - E.N. 114

• Location – Coruche

• Construction – 1932

• Overall length - 40m

• Spans – 1

• Deck overall width – 9m

• Is one of three identical bridges

located in Sorraia river valley

Coroa Bridge

Structural Solution

Two Pratt truss made by

composite profiles performed with

riveted steel plates

Superstructure of metallic simply

supported spans

Concrete abutments

lined with natural stoneConcrete deck supported by

metallic transverse floor beams

and stringers

Coroa Bridge

Structural Assessment Conclusions

• Abutments – Low bearing capacity for seismic design action;

Since the abutments presented no signs of cracks or settlement it was considered that the cost of reinforcement and the complexity of the work didn’t compensate the benefict of the reinforcement. In addition the expected duration of the intervention would be incompatible with the traffic closure deadline on the bridge.

Thus a simpler and more economic intervention that also improved the seismic behavior of the structure was assessed.

Coroa Bridge

Seismic retrofitting solutions

• Reduction of deck permanent load:

- Elimination of the filling layer between the concrete slab and the pavement

and use of structural lightweight concrete in order to reduce the oscillating

mass and thus the seismic forces to be transmitted to the abutments.

Coroa Bridge

Seismic retrofitting solutions

• New deck connection system:

- Replacement of existing bearings

for high dumping rubber bearings

(HDRB), allowing substantial

decrease and the distribution of

longitudinal seismic forces transmited

to the abutments.

Coroa Bridge

Venture Data

Contract Value 220.734,74 €

Seismic Retrofit Works 62.097,75 € (28%)

Designer:LISCONCEBE – Consultadoria de Projectos de Engenharia, Lda.

Contractor:CONDURIL – Construtora Duriense, S.A.

Case Histories

Santa Margarida do Sado Bridge VNMilfontes BridgeNS Guia Bridge

Eng.º Jorge Moreira BridgeCoroa Bridge

Eng.º Jorge Moreira Bridge

Overview

• Roadway - E.R. 266

• Location – Odemira

• Construction – 1955

• Overall length - 128 m

• Spans – 13

• Deck overall width – 9.40m

Eng.º Jorge Moreira Bridge

Structural Solution

• Reinforced concrete deck, with eight cantilever spans of 29m and three simply-supported spans of 3.80m each. The isostatic structure is formed by Gerber type slab;

• The deck is a solid reinforced concrete slab with variable height, 0.88m on the piers and 0.47m at the mid-span;

• The reinforced concrete piers are wall-type and footing founded while the abutments are made of concrete.

Eng.º Jorge Moreira Bridge

Structural Assessment Conclusions

• Piers and foundations – Low bearing capacity for seismic design action;

It was decided to implement a local intervention at the deck joints instead of a typical strengthening solution of all piers. Although the structural behavior is changed concerning the temperature action, it was verified its feasibility taking to account the bridge overall length and the flexibility of the piers and foundations.

Eng.º Jorge Moreira Bridge

Seismic retrofitting solutions

• Continuity of the deck in terms of axial loads:

- Connection between adjacent spans through metal plates fixed with steel

bars;

- Elimination of joints through the sealing with cement based mortar;

Eng.º Jorge Moreira Bridge

Seismic retrofitting solutions

• Abutments modification:

- Concerning the structure performance modification caused by the

continuity between spans, the resulting displacements forced the

introduction of neoprene expansion joints at the ends of the bridge.

Eng.º Jorge Moreira Bridge

Venture Data

Contract Value 380.683,08 €

Seismic Retrofit Works 117.066,13 € (30%)

Designer:A2P CONSULT – Estudos e Projectos, Lda.

Contractor:TECNOVIA – Sociedade de Empreitadas, S.A.

Thank you for your attention