速度脉冲地震作用下偏心结构的弹塑性抗震研究

研究速度脉冲地震下,刚度偏心、强度偏心和两者组合偏心体系的弹塑性抗震需求。基于新开发的变轴力-双向弯曲模型,选取8条速度脉冲地震记录,进行了强速度脉冲地震效应和偏心布置双重不利条件下单层RC框架结构的弹塑性动力时程分析,讨论了结构的延性、位移、扭矩和扭转角变化规律。结果表明,偏心结构在速度脉冲工况下比在非速度脉冲工况下有更大的弹塑性抗震需求;刚度偏心对结构弹塑性抗震需求不敏感,强度偏心对弹塑性抗震需求的影响最为显著,组合偏心的影响介于两者之间。随强度偏心率增大,弱侧延性需求呈非线性急剧增大,最大达到对称结构延性需求的3.09倍,位移、扭矩和扭转角也迅速增大,偏心率为0.2时扭转角为偏心率为0.05时的6.4倍;建议偏心结构弹塑性分析时宜增加强度偏心作为基本参数,并考虑速度脉冲地震效应。

ELASTOPLASTIC ASEISMIC RESEARCH ON ECCENTRIC STRUCTURES SUBJECTED TO VELOCITY PULSE-LIKE GROUND MOTION

The elastoplastic seismic demand of structural systems, with stiffness, strength and combined eccentricity, subjected to pulse-like ground motions is investigated. Based on the newly-developed varying axial load-biaxial bending model, nonlinear time history analysis is conducted to study a single-storey RC frame subjected to eight ground motions, considering the pulse effect and eccentricity. The results of ductility, drift, torsion and rotation are discussed. The results show that eccentric system experiences higher elastoplastic demand under pulse-like cases compared with non-pulse-like cases. The stiffness eccentricity is insensitive to elastoplastic response, while the strength eccentricity has the most influences. The ductility in the weak side increases greatly with increasing strength eccentricity, and the maximum ductility is 3.09 times higher than that of symmetric structure. At the same time, the drift, torsion and rotation increase rapidly, and the rotation with eccentricity ratio of 0.2 is 6.4 times higher than that of 0.05. It is suggested that the strength eccentricity should be considered as a parameter in elastoplastic analysis of eccentric systems, and the velocity pulse-like effect should also be considered.