Estimation Of Seismic Residual Displacement For Reinforced Concrete Bridge Columns

Japanese scholars began to study residual displacement of the pier, and add its checking calculation content to the bridge seismic specification since the Kobe earthquake in1995. However, as the mechanism of the bridge piers’residual displacement is not clear and the problems in facets of the bending deformation of pier and the slip deformation of bottom longitudinal reinforcement lack profound analysis, it is difficult to estimate residual displacement of bridge piers under the earthquake.Firstly, both of our team and Lehman’s established the pseudo-static test numerical models by using OpenSees. Based on the comparison of hysteresis curve and experiment, when considering slip effect of longitudinal reinforcement, it is better to explain hysteretic performance of bridge piers, assess elastic stiffness and horizontal yield load and estimate the ratio of the slip deformation of reinforcing bars in total displacement at the pier top.Secondly, the study including the effects of the longitudinal reinforcement bond-slip constitutive model’s parameters to the hysteresis curve and the composition of the pier deformation, Suggests that the ultimate strength of longitudinal reinforcement value is more sensitive. Subject to the experimentally obtained hysteresis curves and the proportion that longitudinal reinforcement bond slip deformation in the total lateral displacement of pier, we identify the reasonable values longitudinal reinforcement bond-slip constitutive model’s parameters of the specimen piers completed by Lehman and the expansion prototype piers.Finally, we study some influence factors of the seismic residual displacement of reinforced concrete bridge piers, including ground motion category, peak acceleration, structural factors (longitudinal reinforcement ratio, shear span ratio), the maximum drift ratio of pier and displacement ductility, etc. By comparing the drift ratio of pier, residual drift ratio and longitudinal reinforcement slip composition under the function of ground motion, we can conclude that:(1) Seism motion category is the significant factor of effecting on pier earthquake residual drift ratio. Under action of the near-fault seismic oscillation,pier residual drift ratio will be greater than that of far-fault situation. (2) Under the action of near-fault seism motion, the ratio of longitudinal reinforcement slip composition in the pier drift ratio is between30%-50%, which of far faults is general20%-40%or less.(3) Under the action of near-fault seism motion, the ratio of longitudinal reinforcement slip composition in the pier residual drift ratio is between10%-60%, which of far faults is general less than20%.(4) When reaching to2%-3%of pier drift ratio or more than3of the displacement ductility coefficient, its seismic residual displacement ratio will be significantly enlarged, and also the contribution of the reinforcement bars’bond slip to residual displacement has an increasing tendency.