EC, Programme Environment and Climate

EC Programme Environment and Climate

Advanced Methods for Assessing the Seismic Vulnerability of Existing Motorway Bridges (VAB)

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.

The following international consortium has prepared the proposal for the Environment and Climate Programme of EC:

ÖFPZ ARSENAL Ges.m.b.H. (Austria), Coordinator

ISMES S.P.A. (Italy)

ICTP, International Center for Theoretical Physics (Trieste, Italy)

SETRA (France)

UPORTO, Universidade do Porto (Portugal)

CIMNE, International Centre for Numerical Methods in Engineering (Spain)

JRC, Joint Research Centre, Ispra (EU)

Recently the consortium was informed that the proposal got an A1 rating and that contract negotiation will be started. The following working programme is planned:

Dynamic in-situ testing will be used to identify the actual bridge properties including soil-structure interaction effects and to characterise the surrounding soil for Motorway Bridge WARTH on Austrian Southern Motorway.

A preliminary FE model predicting the linear bridge response including the support boundary conditions will be elaborated and updated using the measured results.

Numerical modelling for simulating the nonlinear behaviour of bridge piers under severe earthquake loading using damage mechanics concepts will be carried out.

Realistically large bridge piers with rectangular hollow cross section will be physically tested in order to calibrate numerical models and to assess the ductility demand and capacity. Tests will be performed using the pseudo-dynamic method with sub-structuring of the bridge deck of bridge WARTH which will be numerically simulated using the updated FE - model.

The effects on the bridge seismic response of asynchronous motion at the base of the bridge piers will be analysed. The objective is to define in a realistic way the seismic input of the specific sites of interest through the computation of realistic synthetic broadband records, taking into consideration source, path and local effects.

Simplified analysis tools for assessing the vulnerability of complete bridges will be developed.

Seismic retrofitting measures will be developed in order to improve bridge reliability, including an evaluation of intervention costs.

Rainer Flesch