Research On The Seismic Risk Management Of Bridges In One City In North Of China

The seismic damages to bridges during the Wenchuan Earthquake have demonstrated the seismic vulnerability of the bridges.To ensure the seismic safety of bridges,the seismic risk evaluation and countermeasures for the bridges in one city of north China are conducted.The research is conducted based on lessons from the damaged bridges,field investigation of the bridges,and analytic hierarchy process-fuzzy comprehensive evaluation method.The main conclusions are summarized as follows:(1)Field investigations for the seismic risk of a total of 85 bridges in the city are conducted.It is found that a total of 33 bridges would be damaged during a major eartqhuake.By researching the damaged bridges during the past earthquakes,it could be concluded that the main factors influencing the seismic risk of the bridges are foundation,bridge pier,abutment,bearing,beam and shear key of the bridge.(2)The weight coefficients for various parts of the bridge are studied by analytic hierarchy process method.The coefficients between the foundation,pier,beam,abutment,bearing and shear keys are 0.452:0.238:0.113:0.113:0.054:0.03.Then,fuzzy comprehensive evaluation method is used to evaluate the seismic risk of one bridge.It is found that the evaluation result by the fuzzy comprehensive evaluation method agreed well with the filed investigation result.The seismic risk grade of the bridge could be obtained by quantitative analysis by using fuzzy comprehensive evaluation method,which is rational than the field investigation result.(3)The analytic hierarchy process-fuzzy comprehensive evaluation method model for the whole traffic system of the city is built by comsidering all the 85 bridges in the city,and the seismic risk evaluation for the whold traffic system of the city is conducted.It is found that the traffic system would behave well during an earthquake.Although some bridges would be destroyed,the expressway and the national highway in the city would be little influenced,and the lifeline of the city would be safe.(4)Among the 33 bridges with large seismic risk,a total of 23 bridges are induced by poor construction quality and long service time,account for 69.7%of all the seismic unqualified bridges.A total of 10 bridges are induced by unreasonable design method,account for 30.3%of the seismic unqualified bridges.It could be concluded that most of the seismic unqualified bridges are induced by management reason,while the percentage of the seismic unqualified bridge induced by technique reason is relatively small.(5)The countermeasures for the seismic risk of the bridges are proposed.Such as special attention should.be paid by the government,paying special attention for middle and small bridge construction management and routine maintenance,demolishing bridges with long service time,and retrofit should be conducted to some important bridges.