Seismic Retrofit of Bridges
“EP – Estradas de Portugal” Experience
Tiago Rodrigues, Estradas de Portugal
Workshop
DynamicPerformance, Assessment & Rehabilitation of Structures
Monte 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 System
EP 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 Retrofitting
The Bridge Conservation Management System allows prioritization of interventions
depending on the severity of the anomalies in each structure.
Intervention is necessary
Structural Assessment
Seismic 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
Coroa Bridge
NS Guia Bridge
VNMilfontes Bridge
Eng.º Jorge Moreira 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 simplysupported spans
Two Pratt truss made by
composite profiles performed with
riveted steel plates
Pier and abutments
made of limestone
masonry
Concrete deck supported by
metallic transverse floor beams
and stringers
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
Seismic Retrofit Works
Designer:
A2P CONSULT – Estudos e Projectos, Lda.
Contractor:
TECNOVIA – Sociedade de Empreitadas, S.A.
620.183,47 €
35.956,65 € (6%)
Case Histories
Santa Margarida do Sado
Bridge
Coroa Bridge
NS Guia Bridge
VNMilfontes Bridge
Eng.º Jorge Moreira 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 f1.20m, 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
Seismic Retrofit Works
Designer:
BETAR - Consultores, Lda.
Contractor:
OBRECOL – Obras e Construções, S.A.
1.290.000,01 €
185.412,96 € (15%)
Case Histories
Santa Margarida do Sado
Bridge
Coroa Bridge
NS Guia Bridge
VNMilfontes Bridge
Eng.º Jorge Moreira 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;
•
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;
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.
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
•
Longitudinal displacements control system of independent spans:
- Introduction of longitudinal movement control system of the independent
spans which minimize the risk of failure for lack of support.
Vila Nova de Milfontes Bridge
Venture Data
Contract Value
Seismic Retrofit Works
Designer:
A2P CONSULT – Estudos e Projectos, Lda.
Contractor:
OBRECOL – Obras e Construções, S.A.
1.397.529,42 €
333.626,55 € (24%)
Case Histories
Santa Margarida do Sado
Bridge
Coroa Bridge
NS Guia Bridge
VNMilfontes Bridge
Eng.º Jorge Moreira 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
Superstructure of metallic simply
supported spans
composite profiles performed with
riveted steel plates
Concrete abutments
lined with natural
stone
Concrete 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
220.734,74 €
Contract Value
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
Coroa Bridge
NS Guia Bridge
VNMilfontes Bridge
Eng.º Jorge Moreira 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
introduction of neoprene expansion joints at the ends of the bridge.
the
Eng.º Jorge Moreira Bridge
Venture Data
380.683,08 €
Contract Value
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