不等强混凝土空间中节点抗震性能研究及其受剪承载力计算

Seismic performance of 3D interior joints with different concrete strength and shear capacity calculation

为研究节点核心区采用与梁等强度的低强度混凝土浇筑的夹心节点的抗震性能,通过3组不同柱与梁混凝土强度比的空间夹心节点和传统节点(节点核心区混凝土与柱等强)的对比试件在双向低周往复荷载作用的性能试验研究,对比分析了各组试件的破坏形态、延性、耗能、变形等差异。研究结果表明:中低剪压比夹心节点的整体抗震性能稍弱于传统节点,相差不明显;中低轴压比、剪压比条件下,当柱与梁混凝土强度比小于1.5时,节点区可直接采用与梁相同强度的混凝土浇筑,当柱与梁混凝土强度比大于1.5时,其破坏形式转变为节点核心区剪切破坏,需采取相应的结构措施予以加强;采用平面节点软化拉-压杆模型,建立了承受双向水平荷载的空间节点软化拉-压杆受剪模型与受剪承载力的计算式,并将其计算结果与试验结果进行了校验,两者吻合较好。

In order to study the seismic performance of 3D interior sandwich joints core area made of low strength concrete the same as beams,three groups of specimens with different concrete strength grades,each consisting of three sandwich joints and three corresponding additional joints with higher strength concrete the same as columns were tested under bi-directional reversed cyclic loads. Performance indexes such as the failure mode,ductility,energy dissipation and deformation of the two kinds of joints were analyzed contrastively. Results show that the seismic performance of sandwich joints is insignificantly weaker than traditional joints in the condition of mid-low shear compression ratio. In the condition of mid-low axial compression ratio and shear compression ratio,when the strength ratio of the column and beam is less than 1. 5,the joints core area can be cast with the low strength concrete the same as beams. Otherwise,the failure mode may change from the flexural failure of the beams to the shear failure of the core,and additional strengthening measures are inevitable. At last,based on the plane softened strut-and-tie model,the 3D softened strutand-tie shear model and shear capacity calculation formula under bi-direction horizontal loads are proposed,and the solutions agree well with the experimental results.