Study On Selection Of High Pier Bridges In High Altitude Canyon Zone Based On Seismic Performance

With the advancement of our country's strategy of developing the western region,the construction of highway and Bridge in the northwest region has met with great opportunities for development.The northwest region has the topographic characteristics of mountains and valleys,so the construction of high pier bridges is particularly common,and the construction of high piers will face many difficult problems.Seismic performance is one of them.Pier cross-section form and pier-beam connection form are important factors affecting the seismic performance of bridge structures.Therefore,in the design of high pier bridges,the pier section form and pier-beam connection form have become a key consideration.In view of the influence of these two factors,the following work has been done in this paper:(1)Combining with the general situation of Wolonggou No.4 Bridge in Qinghai Province,under the condition that the area of concrete section and reinforcement ratio of section are the same,the high pier models with rectangular hollow pier,square hollow pier and circular hollow pier are established.Pushover analysis is carried out by means of mode combination lateral force pushing-down method.The pushing-down results show that the seismic performance of pier with rectangular hollow section is the best.OK.The influence of pier height on seismic performance of piers is still studied by mode combination lateral force pushing method.The results show that when the pier reaches 50 m,the seismic performance of piers decreases gradually with the increase of pier height.(2)According to the engineering example in this paper,two kinds of full bridge models of pier-beam consolidation and bearing connection are established,and the seismic response analysis of the two schemes is carried out by response spectrum method and dynamic time history analysis method.The analysis results show that the internal force response value of the structure is smaller,but the displacement response value is larger,the transverse displacement is too large,which will cause beam falling,the longitudinal displacement is too large,which will cause the main beam collision of adjacent spans;while the internal force response value of the structure with pier-beam consolidation is bigger,but the overall stiffness of the structure itself is bigger,and the bending and overturning resistance ability is stronger,only need to use pier-beam consolidation.The seismic design of the main girder should be strengthened,and the displacement response value of the structure is very small,only the support block and expansion joint can be set up.Therefore,the pier-beam consolidation method is better for small-span high pier bridges similar to the engineering examples in this paper.