高强混凝土框架柱的恢复力模型研究

STUDY ON RESILIENCE MODELS OF HIGH-STRENGTH CONCRETE FRAME COLUMNS

根据108根高强混凝土框架柱在固定轴向荷载和水平反复荷载作用下的试验结果,分析和回归出试验柱的骨架曲线强化段水平投影长度、最大荷载与屈服荷载的比值和各刚度与剪跨比、轴压比、配箍特征值及总横截面面积与核心混凝土面积比值之间的关系。根据高强混凝土框架柱屈服时截面平衡条件推导出的屈服柱顶水平荷载和水平位移、按《混凝土结构设计规范》计算出的柱顶峰值水平荷载及有关试验回归公式确定出高强混凝土框架柱恢复力模型的骨架曲线及滞回曲线。研究表明:试验骨架曲线强化段在水平投影长度和屈服位移的比值与配箍特征值成正比,与轴压比、剪跨比和总横截面面积与核心混凝土面积比值成反比;试件的弹性刚度、强化刚度及退化刚度与轴压比和总横截面面积与核心混凝土面积比值成正比,与配箍特征值和剪跨比成反比;建议的恢复力模型考虑了多种影响因素,与试验结果相接近,且便于工程应用。

Based on the experimental results of 108 high-strength concrete frame columns under constant axial loading and horizontal cyclic loading, the relationships among the horizontal projective length of strengthened portions, the ratios of maximum loads to yielding loads, the various rigidities of testing columns and shear span-to-depth ratios, the axial compression ratios, the transverse reinforcement characteristic values, and the ratios of gross cross-section areas to confined core concrete areas are analyzed and regressed. The horizontal displacements and loads at column tops are deduced according to the equilibrium conditions on the cross-section at yield. The lateral maximum loads at column tops are calculated according to the current Chinese concrete code. Regressive formulas are then used to establish the resilience models of high-strength concrete frame columns. The main results show that the ratios of the horizontal projective length of strengthened portions to the yielding displacements are directly proportional to the transverse reinforcement characteristic values and inversely proportional to the axial compression ratios, shear span-depth ratios and the ratios of gross cross-section areas to confined core concrete areas; the elastic rigidities, stiffened rigidities and degraded rigidities of specimens change proportionally with axial compression ratios and the ratios of gross cross-section areas to confined core concrete areas and change inversely with the transverse reinforcement characteristic values and shear span-depth ratios; the resilience models of high-strength concrete frame columns proposed consider various influential factors and are close to the experimental results and can be conveniently applied for practical purpose.