初始扭矩下全装配预应力混凝土梁端界面弯扭性能试验研究

Test study on interfacial flexural-torsional performance of unbonded post-tensioned precast concrete beam end under initial torsion

为了研究初始扭矩作用下全装配预应力混凝土矩形截面梁端界面的弯扭性能,设计了2组共8个不同配筋及不同初始扭矩的装配式预应力混凝土梁柱边节点,并对其进行拟静力试验。对比研究梁端的受扭变形和承载力、裂缝分布特征以及受弯滞回性能等。结果表明:屈服位移角后,随着位移角增加,梁端界面耗能钢筋屈服耗能,受压区高度减小,界面受扭承载力降低,界面受扭承载力主要由界面预应力筋作用下的静摩擦力承担;界面抗扭失效后的扭转变形不可恢复,扭转变形随着位移角的逐级循环加载而累积增加;扭弯比为0.02、0.04和0.06的扭矩作用时,抗扭失效后的扭转变形导致耗能钢筋剪弯变形,其对极限位移角下的梁端受弯滞回性能和自复位性能有不利影响,但影响较小;增加耗能钢筋配筋量不能有效提高节点屈服后的界面受扭性能,增加预应力筋配筋量能提高极限位移角下的界面受扭承载力,但承载力较低。

To investigate the flexural-torsional performance of the connection interface of unbonded post-tensioned precast concrete beams under initial torque,quasi-static cyclic tests were carried out.Two groups of eight specimens with different reinforcement ratios and different initial torques were tested to study the differences in the torsional deformation and capacity,crack distribution,flexural hysteretic behavior and so on.The test results show that after the yielding drift ratio,with the increase of drift ratio,the rebars yield to dissipate energy significantly,the compressive depth of concrete decreases obviously,while the torsional capacity of the interface decreases and is mainly resisted by static friction under the action of prestressed tendon at the interface.After the torsional failure,the torsional deformation cannot be recovered and accumulates with the cycling drift loading.Under the initial torsion with different torsion moment ratios(0.02,0.04 and 0.06),the torsional deformation after the torsional failure leads to shear-bending deformation of energy dissipating bars,which has a slightly negative effect on the bending hysteresis and self-centering performance of the beam end at the ultimate drift ratio.The increase of the amount of energy dissipating rebars cannot effectively improve the torsional capacity after the yielding drift ratio,while the increase of the amount of prestressed tendons can improve the torsional capacity at the ultimate drift ratio,but the improvement is limited.