节点张开后刚度对变摩擦耗能自复位预应力混凝土框架抗震性能的影响分析

Influence of Joint Stiffness After Gap Opening on Seismic Performance of Self-Centering Prestressed Concrete Frames with Variable Friction Dampers

自复位预应力混凝土(SCPC)框架在梁柱节点张开后的刚度显著降低,导致罕遇地震下结构的层间侧移角较大。利用具有第三刚度的变摩擦(VFD)耗能SCPC节点构造可有效提高结构罕遇地震下刚度,降低层间侧移。选择我国8度设防地区的一VFD-SCPC框架为分析算例,利用OpenSees分析软件建立其有限元模型。以12条地震波为输入,研究节点张开后刚度(第二刚度和第三刚度)对VFD-SCPC框架抗震性能的影响。结果表明:增大节点的第二刚度可以降低罕遇地震下结构的层间侧移角,但不会改变层间侧移的分布模式;增加节点的第三刚度不仅可以显著降低结构的层间侧移角和柱内力,且可以降低结构的高阶模态效应,从而降低上部楼层的层间变形,同时保证较好的复位效果。

Due to the decrease of the joint stiffness after gap opening for the self-centering prestressed concrete(SCPC) frames, the inter-story drift of structures under rare earthquakes has increased obviously. The SCPC beam-to-column joints with variable friction dampers(VFD), characterized by a third stiffness, is useful to improve the stiffness of structures under major earthquakes, so as to decrease the inter-story drift of structures. A VFD-SCPC frame located in the area with a seismic fortification intensity of eight degree was taken as the analytical case. The numerical model was established via nonlinear finite software OpenSees, and 12 earthquake waves were used as the excitation to study the influence of the connection stiffness after gap opening, including the second and third stiffness, on the seismic performance of VFD-SCPC frames. The results showed that increasing the second stiffness could reduce the inter-story drift for entire structures, while the distribution of lateral deformation could not be changed. While increasing the third stiffness was not only useful to decrease the inter-story drift and column moment, but also beneficial to decrease the higher mode effect so as to decrease the deformation of higher stories, guaranteeing the expected re-centering effect.