预应力型钢混凝土双坡框架抗震性能试验研究

Experimental study on seismic behavior of prestressed steel reinforced concrete frame with double-pitches

为研究预应力型钢混凝土双坡框架的抗震性能和破坏机理,基于同等承载能力条件设计缩尺比为1∶4的1榀预应力混凝土双坡框架(PC-F)和1榀预应力型钢混凝土双坡框架(PSC-F),并对其进行竖向荷载和水平低周反复荷载共同作用下的加载试验,得到框架的裂缝开展和分布及破坏形态特征、滞回曲线、骨架曲线、延性、刚度退化、等效黏滞系数、总耗能和位移恢复能力等抗震性能指标。试验结果表明:同等承载力条件下,预应力型钢混凝土双坡框架具有更优越的抗剪能力和抗震性能;相较于预应力混凝土双坡框架,预应力型钢混凝土双坡框架的开裂荷载提高了70%;型钢的存在使得预应力混凝土双坡框架的破坏机制由两铰(柱-斜坡梁节点)破坏转变为四铰(柱-斜坡梁节点、斜坡梁-水平梁节点)破坏,每个塑性铰部位呈现典型的弯曲延性破坏特征;相较于预应力混凝土双坡框架,预应力型钢混凝土双坡框架滞回环近似梭形更加饱满,峰值荷载后承载力退化及刚度退化更加缓慢,位移延性系数、等效黏滞阻尼系数、总耗能分别提高了9.27%、30.6%、53.5%,位移恢复能力系数降低27.5%。

In order to investigate the seismic behavior and failure mechanism of prestressed steel reinforced concrete frame with double-pitches, two specimens of prestressed concrete frame(denoted by PC-F) and prestressed steel reinforced concrete frame(denoted by PSC-F) with 1∶4 scale ratio were designed based on the same bearing capacity condition, the load tests under the combined action of vertical load and horizontal low-frequency cyclic load were carried out. The crack development, distribution and the failure mode characteristics of two specimens were obtained, together with the seismic performance indexes such as hysteresis curve, skeleton curve, ductility, stiffness degradation, equivalent viscosity coefficient, total energy consumption and displacement recovery ability. The test results indicate that PSC-F has better shear capacity and seismic performance under the same bearing capacity. Compared with PC-F, the cracking load of PSC-F increased by 70%. Due to the existence of shaped steel, the failure mechanism of prestressed concrete double-slope frame is changed from two hinges failure(column-slop beam joint) to four hinges failure(column-slop beam joint and slop beam-horizontal beam joint). Each plastic hinge part presents typical bending ductile failure characteristics. Compared with PC-F, PSC-F has fuller hysteretic loops, slower degradation of bearing capacity and stiffness after peak load. The ductility coefficient, equivalent viscous damping coefficient and total energy consumption are increased by 9.27%, 30.6% and 53.5% respectively, and the displacement recovery capacity coefficient is reduced by 27.5%.