近断层地震下大底盘框架结构非线性响应分析及减震控制

Nonlinear response analysis and shock absorption control of R. C. structures with large chassis under near-fault ground motions

近断层地震动具有加速度、速度脉冲运动特性,其对大底盘框架抗震结构可能造成更为不利的影响。本文建立一幢大底盘钢筋混凝土框架结构有限元模型,梁柱塑性铰采用集中铰,考虑结构的非线性性能,以3条普通地震动与3条近断层地震动记录为输入激励,对结构进行动力弹塑性时程分析,揭示近断层地震动作用下结构的非线性响应规律,并对近断层地震下的结构响应进行减震控制。结果表明:在地震动强度指标相同时近断层地震动作用下结构的地震响应相比普通地震动下明显增大,且罕遇地震下结构的弹塑性层间位移角均大于1/50,不能满足抗震要求;增设黏滞阻尼器的消能减震体系能够有效控制结构的非线性响应,降低近断层地震动作用下的结构损伤,为工程结构在近场地区的设计提供参考。

Near-fault ground motions were featured by acceleration and velocity pulses,which may cause the adverse influence on the R.C.structures with large chassis.The finite element model of a reinforced concrete frame structure with large chassis was established,in which the plastic hinges in the beam and column adopted the concentrated hinge because of nonlinear performance of the structure.The records of three near-fault ground motions as well as three common ground motions were chosen as input excitation,and the dynamic elastic-plastic time history analysis of the structure is carried out to reveal the law of nonlinear seismic responses of the structure.Further,the control method of shock absorption was proposed.The results show that the seismic responses of the structure under near-fault pulse ground motions are significantly greater than those under the common ground motions,and the inter-story drift ratio when subjected to the rare near-fault pulse ground motions is greater than 1/50,which does not meet the seismic requirement.The nonlinear responses of the structure can be effectively controlled by adding the viscous dampers and the damage of structures are significantly reduced under near-fault pulse ground motions.This study provides references for the engineering structure design in the near field area.