Study On Evaluation Method Of Seismic Performance Of Bridge High Piers In Mountain Area

China's seismic research on bridge structures has been in the development stage,especially for the high-pier and long-span bridges prone to appear in the southwest of China.It is not enough to meet the needs of actual projects,resulting in the difficulties of earthquake resistance and economic losses of the bridge structures.Based on the performance-based seismic design method,this paper uses the nonlinear static analysis method(Pushover analysis method)and the incremental dynamic elastoplastic analysis method(IDA analysis method)to analyze the seismic performance evaluation methods for high-pier and long-span concrete bridges.Pushover analysis method improvements and applicability.The work accomplished by this article mainly includes the following points:(1)Introduce the development of evaluation methods for seismic performance of bridge structures;outline the basic principles of Pushover analysis methods,specific implementation steps,and the existing distribution of lateral loads,and propose how to consider the concentrated quality of superstructure equivalents.Pushover lateral load distribution pattern when the block and the top of the pier are relatively slipped(Form6);(2)Enumerate five types of fixed lateral load distributions that are widely used,combined with the Pushover lateral load distributions proposed in this paper that take into account the equivalent upper-structure equivalent mass and the top of the pier where the slip occurs.(Form 6)Pushover analysis was carried out for six types of fixed lateral load distributions for different height pier structures.The comparison of the results shows that the form of the six-distribution proposed in this paper can take into account the influence of the high-order mode of vibration and the influence of the mass of the superstructure,which is a more reasonable form of lateral load distribution;(3)Considering the difference in performance of piers with different cross-sectional shapes(with constant cross-sectional shape along the height of piers)under earthquakes,the existing lateral load distribution forms and the form of the six distributions proposed in this paper are different for the same height.Pushover analysis was performed on piers with cross-sectional shapes to compare the performance of bridge piers with different cross-sectional shapes under earthquakes.The rationality ofthe formal six-distribution form proposed in this paper was further verified;considering the piers with varying cross-sectional shapes along the height of the piers,consider According to the difference of the initial anti-lateral stiffness of each equivalent layer of height,the existing equivalent basic mode distribution form(Form 2)is optimized.The results show that the accuracy of the Pushover result under the optimized form two distribution form is greatly improved;(4)For the bridge structure of the project selected in this paper,using the Pushover displacement-shear curve in the form of six distributions,convert the capacity spectrum curve and the demand spectrum curve to obtain structural performance points,and evaluate the seismic performance.The results show that the bridge Meet the seismic requirements.