Study On Seismic Performance Evaluation Method Of Existing Highway Beam Bridge

China is located in the east of Eurasia and the west bank of the Pacific Ocean.Affected by CircumPacific seismic belt and Eurasian seismic belt,it is a semi-landlocked country with frequent earthquakes.Because highway bridges are of utmost importance for highway traffic,their serious damage in an earthquake will slow down or even paralyze the entire relief work,which may finally cause serious economic losses and heavy casualties.Even though the total number of highway bridges in China ranks first in the world,most of them are old bridges with long service life and have high seismic vulnerability,hence it is particularly urgent and necessary to make a systematic and effective evaluation of the seismic performance of these existing bridges.However,at present,there is no promulgated and implemented standard or norm for the seismic performance evaluation of bridges in China,and the traditional empirical statistical method also has obvious deficiencies.In view of this,in this paper the author intends to establish a set of efficient,accurate and operable seismic performance evaluation method for existing highway bridges,so as to realize the seismic performance evaluation of existing highway bridges and guide seismic reinforcement.Based on the seismic performance investigation project of existing highway bridges in Ningxia,by referring to advanced research achievements at home and abroad,and in combination with Specifications for Seismic Design of Highway Bridges(JTG/T 2231-01—2020)in China,the author develops a twolevel evaluation method for seismic performance of existing highway girder bridges with a span of no more than 150 meters for a single hole.In this paper,firstly,the analytic hierarchy process(AHP)was used to establish the first-level evaluation method for seismic performance of existing highway bridges,the influence indexes considered in the evaluation are introduced in detail,and the critical values of different influence degrees of the same index are defined,so that different evaluators can refer to consistent objective standards in the evaluation.Nevertheless,it is considered that the existing highway bridges are constantly affected by complex environment with the increase of their service life,especially the erosion of chloride ions make the material properties of bridge structural components continue to deteriorate.Thus,based on the study of the traditional capacity demand ratio method,the mechanical properties of concrete and steel materials after deterioration,this paper develops a secondary evaluation method for the seismic performance of existing highway bridges,which takes the component capacity demand ratio after material property deterioration as an index.Finally,the seismic performance of existing highway bridges in Ningxia was evaluated by means of the two-level evaluation method.The evaluation example verifies the good accuracy and applicability of this method,and the evaluation results can clearly show the seismic performance of the evaluated bridges and their deficiencies.Moreover,according to the evaluation results,the seismic reinforcement of bridge structure can be guided so as to obtain the maximum social and economic benefits.