锚固力在钢筋黏结和端板承压间的分配规律

Distribution regulation of the reinforcement force between bond and headed bars

摘要:

为获得锚固力在高强热轧钢筋直锚段黏结和端部锚固板承压间的分配规律，以钢筋与混凝土间的黏结-滑移本构关系为基础，利用MATLAB编写出带锚固板钢筋受力计算程序，并通过120个带锚固板钢筋混凝土试件的拉拔试验结果对程序的准确性进行验证.依托程序，分析相对保护层厚度c/d和钢筋屈服强度与混凝土抗拉强度之比f_y/f_t，对钢筋稳定锚固长度与钢筋公称直径之比l_as/d的影响以及钢筋屈服强度、混凝土强度等级、混凝土相对保护层厚度、钢筋相对埋置长度等参数对直锚段钢筋黏结应力f_b的影响，并拟合得到以f_y/f_t和c/d为自变量的l_as/d计算公式.结果表明:l_as/d随f_y/f_t的增大而线性增大，随c/d的增大而非线性减小；f_b/f_y随钢筋埋置长度与稳定锚固长度之比l_at/l_as的变化规律只与混凝土相对保护层厚度有关.继而通过拟合得到加载端钢筋受拉屈服强度时刻，以c/d和l_at/l_as为自变量的f_b/f_y计算公式.

Abstract:

Based on the bond stress-slip constitutive model between the reinforcement and concrete, a MATLAB program was coded to calculate the force of the headed bars, which was used to obtain the regulation of distribution between bond and headed bars of the high strength hot-roll reinforcement force, and it was validated by the pull-out tests of 120 reinforced concrete specimens. According to the simulation results, the combined effects of the relative concrete cover (the ratio of concrete cover c to bar diameter d) and an index f_y/f_t indicating the ratio of reinforcement yield strength to concrete tensile strength were investigated quantitatively. The results indicate that l_as/d (the ratio of the stable development length to bar diameter) increases linearly with f_y/f_t increase, but gradually decreases with the increasing c/d. The formula of l_as/d for f_y/f_t and c/d was established, and the potential influence factors of the bond stress f_b were evaluated, including reinforcement yield strength, concrete tensile strength, the relative concrete cover and the embedment length l_at. The results indicate that c/d is the only factor to constrain the parameter f_b/f_y to be varied with the index l_at/l_as. A reliable calculation formula of the f_b/f_y for c/d and l_at/l_as was proposed.