基于软化拉-压杆模型的对角斜筋ECC连梁恢复力骨架曲线

Skeleton curve of restoring force of diagonally reinforced ECC coupling beam based on softened strut-and-tie model

为了模拟对角斜筋超高韧性水泥基复合材料(ECC)连梁在低周反复荷载下的受力性能,提出了一种计算对角斜筋ECC连梁恢复力骨架曲线的理论模型.该模型基于软化拉压杆模型,由ECC主拉压杆、对角斜筋和次杆组成,并考虑了箍筋对ECC受压性能的约束影响以及ECC受压和受拉时的软化效应.基于此理论模型,提出了对角斜筋ECC连梁受剪承载力计算公式.选取11根对角斜筋ECC连梁实验数据进行验证,得到受剪承载力计算值与实验值之比的平均值为0.94,变异系数为0.09,说明计算结果与实验结果符合较好.在小跨高比连梁中,随着连梁跨高比的增大,对角斜筋和次杆抵抗的剪力逐渐增加,而ECC主拉压杆抵抗的剪力则逐渐减小.

To simulate the behavior of diagonally reinforced engineered cementitious composite(ECC) coupling beam under reversed cyclic loadings, a theoretical model was proposed to predict the skeleton curve of the restoring force of the coupling beam. The proposed model was composed of the main diagonal ECC strut-and-tie, the diagonal reinforcement and the sub-struts based on the softened strut-and-tie model. The restraining effect of stirrups on the compression performance of ECC and the softening effect of ECC under compression and tension were also considered. Based on the proposed model, a formula for calculating the shear capacity of the diagonally reinforced ECC coupling beam was proposed. Eleven diagonally reinforced ECC coupling beam specimens were selected to verify the proposed model. The mean ratio of the calculated shear strength to the measured results is 0.94, and the coefficient of variation is 0.09, showing the good agreement between the calculated values and the experimental results. As for the coupling beams with the small span-to-depth ratio, the shear capacity provided by the diagonal reinforcement and the sub-struts increases with the increase of the span-to-depth ratio of the beam, while the shear capacity provided by the main ECC strut-and-tie decreases.