HRB500/HRB600钢筋作纵筋的混凝土框架梁端弯矩调幅试验研究

为研究HRB500钢筋和HRB600钢筋作纵筋的混凝土框架梁端弯矩调幅规律,完成了12榀单层两跨混凝土框架静力加载试验。试验结果表明:由于受拉纵筋屈服强度提高,一方面梁端塑性铰出现推迟,塑性铰形成前会发生一定的弯矩调幅;另一方面锚固于节点内的梁端受拉纵筋应变渗透引起较大的梁端附加转角,加大了弯矩调幅能力。将试验框架梁端弯矩调幅分塑性铰形成前后两阶段进行考察,第一阶段弯矩调幅幅度为10.35%～33.42%,第二阶段弯矩调幅幅度为3.39%～30.5%。基于试验结果,建立了与梁端控制截面相对受压区高度呈幂函数减小趋势、与受拉纵筋屈服强度和受拉纵筋屈服时刻应变渗透引起的梁端附加转角呈线性增长趋势的第一阶段弯矩调幅系数计算公式;建立了与总塑性转角(塑性铰区范围内的塑性转角与应变渗透引起的梁端附加塑性转角之和)呈幂函数增长趋势、与受拉纵筋屈服强度呈线性减小趋势的第二阶段弯矩调幅系数计算公式。

EXPERIMENTAL STUDY ON THE MOMENT REDISTRIBUTION IN REINFORCED CONERETE FRAMES WITH HRB500/HRB600 STEEL BARS

To study the moment redistribution in the concrete frame beams reinforced with HRB500 and HRB600 steel bars, 12 single-layer and two-span reinforced concrete frames were tested. The test results showed that, due to the increase in the yield strength of the tensile longitudinal steel bars, the formation of the plastic hinges at beam ends was delayed. A certain extent of moment redistribution occurred before the formation of the plastic hinges. In addition, the strain penetration of the steel bars anchored in the joints caused larger additional rotations of beam ends, which increased the moment redistribution. The moment redistribution was investigated in two stages according to whether the plastic hinges were formed or not. The first-stage moment redistribution was between 10.35%~33.42% and the second-stage moment redistribution was between 3.39%~30.5%. Based on the test results, expressions for moment redistribution of the two stages were proposed. The first-stage moment redistribution decreased as a power function with an increase in the relative depth of the compression zone, and increased linearly as the yield strength of the tensile longitudinal reinforcement and the additional rotation at yielding increased. The second-stage moment redistribution increased as a power function with an increase in the total plastic rotation (the sum of the rotation of plastic hinges and the additional plastic rotation due to strain penetration), and decreased linearly as the yield strength of the tensile longitudinal reinforcement increased.