Study On Seismic Performance Of ECC Bridge Pier

Bridge is the transportation channel of traffic,which can cross obstacles and connect traffic routes.As an important part of traffic lifeline,once it is damaged by earthquake,it will cause huge losses.As one of the most important load-bearing structures in bridge structure design,pier column should have good bearing capacity and ductility under shock load.Ordinary concrete itself has weak tensile capacity and poor toughness,which leads to poor ductility of ordinary concrete pier,which is one of the important reasons for seismic damage of long-span bridges.Engineered Cementitious Composite(ECC)is a new type of structural material with high toughness and high crack resistance,which can improve the bending deformation ability of the structure under seismic force.Compared with ordinary concrete,the crack development of ECC is slow and the crack is fine after cracking,which is in line with the characteristics of ductile failure in earthquake.Using ECC material instead of ordinary concrete material in bridge structure can improve the seismic performance of bridge structure and reduce the seismic damage of bridge structure.This paper mainly studies the seismic performance of ECC pier under quasi-static test.The main achievements are as follows(1)The basic mechanical properties of ECC materials with different fiber content were tested.The results show that the tensile strength,toughness and deformation ability of ECC increase significantly with the increase of fiber volume fraction.(2)The quasi-static tests of ECC pier and ordinary concrete pier are completed.The results show that the common concrete pier column falls off seriously after failure,the cracks of ECC pier column are fine and dense,and the surface has better integrity;ECC pier shows excellent bearing capacity and ductility,which can significantly improve the energy dissipation capacity.Compared with the traditional pier with ordinary concrete,ECC pier has better seismic performance.(3)The quasi-static tests of ECC piers with different fiber content were completed.The results show that the peak load and displacement ductility coefficient of ECC pier can be improved by increasing the fiber content;With the increase of fiber content,the area of hysteresis loop in load displacement curve is larger,the shape is fuller,the hysteretic performance is better,and the energy dissipation capacity is greatly improved;The higher the fiber content is,the slower the stiffness degradation rate is.(4)Based on the quasi-static test,the seismic model of ECC bridge pier column is constructed by Diana software.Combined with the orthogonal test method,the influence of fiber content,stirrup reinforcement ratio,longitudinal reinforcement ratio,axial compression ratio,shear span ratio,variable axial force,section shape and other parameters on the seismic performance of bridge pier column is considered.The results show that the longitudinal reinforcement ratio,shear span ratio and axial compression ratio have significant effects on the ultimate bearing capacity of the pier,the shear span ratio and axial compression ratio have significant effects on the ultimate displacement of the pier,and the axial compression ratio has significant effects on the ductility coefficient of the pier;Increasing the fiber content can effectively improve the bearing capacity,ductility and energy dissipation capacity of concrete pier,and with the increase of fiber content,the performance improvement is more obvious;Under the action of variable axial force,the ultimate bearing capacity,ductility and energy dissipation performance of ECC pier columns decrease to a certain extent,and the negative effect of variable axial force on the seismic performance of ECC pier columns is very small;Compared with square columns,the ductility of circular columns is better,and the ultimate bearing capacity of circular columns is almost the same.