A Study On The Seismic Performance Of RC Piers With Small Shear-Span Ratio

In recent years,with the rapid expansion of urban capacity,urban overpasses and their ancillary ramp bridges appear in large numbers.The initial pier is generally a typical short pier with small shear span ratio.The small shear span is more rigid than the short pier.Compared with other piers,the stress is more concentrated and complex in the earthquake damage.Therefore,the small shear span is more likely to cause severe brittle damage when the short pier is subjected to earthquake,which results in the loss of the overall bridge function.Therefore,it will be of great significance and guiding value to carry out the research on seismic performance of short pier with small shear span ratio in time,combining the current engineering practice and scientific research situation.This paper mainly studies the seismic performance of piers with small shear span ratio by means of pseudo static test and open SES numerical simulation(1)Based on the analysis of previous research results and a project example in Southwest China,six reinforced concrete pier models with small shear span ratio reduced by equal scale are made in this paper.The model is designed with longitudinal reinforcement ratio and volume stirrup ratio as variables.(2)Based on the data obtained by pseudo static test,the influence of longitudinal reinforcement ratio,volume hoop ratio and carbon fiber reinforced concrete on the seismic performance of small shear span ratio piers is analyzed by studying the model hysteresis curve,skeleton curve,stiffness analysis,ductility analysis,residual displacement at pier top,energy dissipation capacity and strength attenuation.(3)The finite element model of small shear span ratio short pier is established by using open SES numerical simulation software.By changing some parameters of the verified numerical model,more factors affecting the seismic performance of the piers with small shear span ratio are simulated and calculated.The results show that the stiffness and ultimate bearing capacity of the model increase with the increase of reinforcement ratio of longitudinal reinforcement in the pier shaft,but the overall ductility of the model is poor,and the horizontal displacement of the pier top becomes smaller when the pier is completely damaged.Compared with the different reinforcement ratio of longitudinal reinforcement,the seismic performance of pier model is greatly affected by the different reinforcement ratio of longitudinal reinforcement,and the different volume stirrup ratio has little influence on the seismic performance of pier model.The ultimate bearing capacity,ductility and energy consumption capacity of the model can be improved by the reinforcement of carbon fiber cloth,but the overall stiffness of the pier body has not changed significantly.Increasing the reinforcement ratio and axial compression ratio of the pier model can improve the horizontal bearing capacity of the pier model.However,if the ratio of reinforcement and axial pressure of the pier is increased,the ductility of the bridge pier will be worse when the model is completely damaged.Increasing the shear span ratio of pier model will reduce the horizontal bearing capacity of the pier model.But the ductility of the pier will be worse when the shear span ratio is too small,and the horizontal displacement of the pier top will be smaller when the model is completely damaged.Therefore,when it is inevitable to construct a small shear span pier in engineering practice,the ductility of the pier can be improved by properly reducing the reinforcement ratio of longitudinal reinforcement or pasting carbon fiber cloth after considering the bearing capacity and rigidity of the pier.