摇摆结构体系框架柱脚BRSP耗能机制分析

Energy-dissipation mechanism of BRSPs in column bases of rocking structures

钢框架结构的底层刚性连接柱脚节点在地震时内力大,容易发生损伤破坏,摇摆结构体系中需改变框架柱脚的构造形式以改善结构体系的失效模式并提高结构性能。本文提出一种可抬升的半刚性框架柱脚,设置屈曲约束钢板(buckling restraint steel plate,BRSP)以耗散能量,分别从BRSP与框架柱翼缘的厚度比α、宽度比β和轴向刚度比ω3个方面分析柱脚的滞回性能,并与传统刚接柱脚进行对比。结果表明:随着α和β的增大,构件耗能能力和结构抗侧刚度不断增大,且能较好地减少柱脚的塑性损伤。当α取0.85、β取0.50且ω在[0.3,0.5]范围内时,结构性能最优。BRSP的塑性耗能占总体塑性耗能的比值在80%以上,柱脚的损伤可集中控制在可替换的BRSP内。通过对BRSP与垫板、盖板以及地梁的接触分析表明,盖板不仅能够有效防止BRSP的面外屈曲,还能提供总耗能7%的摩擦耗能量。本文提出的框架柱脚形式具有良好的耗能能力,可以提高结构的抗震性能和可恢复性。

The internal force of rigid column base joints of steel frames is very large under earthquakes,making it prone to be damaged and destroyed,so the configurations of column bases of rocking structures should be optimized to improve the failure modes and structural performance.Lifting semi-rigid frame column base joints with buckling restraint steel plates(BRSPs)were proposed for seismic energy dissipation.The hysteretic behaviors of column base joints with BRSPs were analyzed based on three parameters:thickness ratioα,width ratioβ,and axial stiffness ratioωbetween BRSP and column flange,and the results were compared with those of traditional rigid column base joints.Results show that the energy dissipation capacity of BRSPs and lateral resistance of structures were improved with the increase inαandβ,and the plastic damage of column bases was reduced.The structural performance was optimal under the conditions thatα=0.85,β=0.50,andωwas in the range of[0.3,0.5].The ratio of plastic dissipated energy of BRSPs to the total plastic dissipated energy was more than 80%,and the plastic damage was limited to the replaceable BRSPs.Contact analysis between BRSP,backing plate,cover plate,and base beam was conducted,and it was found that the cover plate could not only effectively restrain the out-plane buckling of the BRSPs,but also provide friction energy dissipation,7%of the total dissipated energy.The proposed column base has great energy dissipation capacity,which can improve the seismic performance and resilience of structures.