Recent seismic events all over the world have shown that bridge structures are particularly sensitive to earthquake loading. There are several reasons for such sensitivity. First many existing bridges were designed without adequate consideration for seismic risk. This has resulted in inadequate detailing of confining steel and insufficient shear reinforcement in the bridge piers, insufficient seat length of bearings, and inadequate strength and stiffness of the superstructure-abutment connection. Furthermore, there are many open questions concerning the ductile behaviour of large bridge piers, in particular those with rectangular hollow cross-section. Also, the seismic zonation map of many European countries has been revised recently, prescribing now higher horizontal ground accelerations in several regions. Finally, local soil conditions and the possibility of asynchronous motion at the base of the piers of long bridges are factors which can cause additional difficulties in properly designing irregular bridges.
There is therefore a need for reliable methods for assessing the seismic vulnerability of existing bridges, in particular large and irregular motorway bridges having lifeline character.
It is the aim of the present project to give a significant contribution to the development of advanced methods for assessing the seismic vulnerability of bridges.To achieve this objective, an international team has been set up covering the following disciplinary tasks contributing to the seismic vulnerability issue:
1. Dynamic in-situ testing to identify the actual bridge properties including soil-structure interaction effects and characterise the surrounding soil;
2. Calibration of numerical models for predicting the linear bridge response (modal analysis), including support boundary conditions;
3. Numerical modelling for simulating the nonlinear behaviour of bridge piers under severe earthquake loading using damage mechanics concepts;
4. Physical testing of realistically large bridge piers with rectangular hollow cross section to calibrate numerical models and assess the ductility demand and capacity. Tests will be performed using the pseudodynamic method with sub-structuring of the bridge deck which will be numerically simulated using a finite element computer code and the output of in-situ testing;
5. Analysis of the effects on the bridge seismic response of asynchronous motion at the base of the bridge piers;
6. Development of simplified analysis tools for assessing the vulnerability of complete bridges;
7. Development of seismic resistance upgrading to improve bridge reliability, including an evaluation of intervention costs.
Funding SchemeCSC - Cost-sharing contracts