Seismic Performance And Design Method Of Rocking Self-centering Columns

There are some new and higher requirements for bridge construction in new era.On the one hand,the bad effect caused by bridge construction on urban traffic and environment should be diminished,and the operating condition needs improvement.In the term of seismic performance,it is significant to achieve the damage control,and the designed bridge structures ought to possess excellent resilience,which is benefit to reduce the post-earthquake repair cost and time.The traditional reinforcing concrete(RC)columns designed by the ductility design method are unable to meet these new requirements,while the rocking-self centering(RSC)columns,as the product of accelerated bridge construction technology,have the potential to be an attractive candidate.If the RSC columns can replace the RC columns in high-intensity earthquake regions,great economic and social value will be created.An effective simulation method is adopted in this study,the seismic behavior of RSC columns is evaluated,and a new RSC double-column bent system equipped with lead-extrusion dampers is proposed.The detailed research contents are listed as follows:(1)Based on the OpenSees platform,the simulation method of the multi-spring model of RSC columns is discussed.The simulated results of skeleton curve are compared,where three different distribution pattern of springs are taken into account.The number of springs is optimized,and a method is proposed to calibrate the springs stiffness.By comparing the simulation and test results of 5 RSC pier specimens,the effectiveness of the simulation method is validated.(2)According to whether columns are equipped with energy dissipation(ED)bars or not,the RSC columns are divided into two categories.Factorial analyses is adopted to investigate the effect of each key design parameter on the hysteretic behavior,and the influence of internal ED bars is focused on.For the RSC columns with ED bars,the self-centering(SC)factor and ED parameter are introduced to explain the distribution of residual drift.Parametric analyses are conducted to study the influence of seven common design parameters on the SC factor and ED parameter.According to the results of these analyses,a simplified formula of residual drift under cyclic loading is proposed through regression analyses.(3)Lead-extrusion dampers(LEDs)are selected as the external energy dissipaters,and a RSC bridge bent system equipped with LEDs(RSC-LEDs)is proposed.With the help of existing test results,a numerical analysis model is established and validated.Parametric analyses are carried out to study the seismic performance of the new system.Semi-empirical formulas used to calculate the effective stiffness and yield strength of RSC-LEDs bridge bents are obtained through regression analyses.Combining the Chinese seismic code and equivalent energy-based design procedure(EEDP),a corresponding two-stage seismic design method is developed.