弯扭复合作用下RC圆形桥墩滞后性能及模型研究

Hysteretic behavior and model study of circular RC bridge piers under cyclic combined flexural and torsional loadings

多维地震作用下,斜交桥和曲线桥梁等非规则桥梁的钢筋混凝土(RC)桥墩受到轴压、弯曲、剪切和扭转复合作用,特别是在扭转作用,引起非规则桥梁RC桥墩弯剪失效,从而影响桥梁结构的抗震性能。为了阐明弯曲和扭转耦合作用对RC圆形桥墩滞后性能的影响,对扭弯比不同的12个RC圆形桥墩进行循环试验研究,评价弯扭相互作用对RC桥墩抗弯性能和抗扭性能的影响,并基于试件的破坏特征以及力和位移关系等试验结果,建立能够预测弯扭相互作用下RC桥墩滞后性能的恢复力模型。结果表明,弯扭相互作用降低了RC桥墩的抗弯和抗扭承载力,桥墩的变形特征和失效模式发生了改变,损伤破坏区域要高于弯曲塑性铰长度区域。提出的考虑扭弯比影响的RC桥墩的弯曲恢复力模型和扭转恢复力模型,可以较好预测弯扭相互作用下RC圆形桥墩的滞回性能。

Reinforced concrete( RC) piers of irregular bridges such as skew or curved bridge may be subjected to a combination of axial load,shear force,flexural moments,and torsional moments under multi-dimensional earthquake excitations. The combined loading,particularly the torsion,may increase the possibility of irregular flexural-shear failure of RC bridge piers,and consequently impair the seismic resistant capacity of bridge structures. To investigate the effect of coupled bending-torsion actions on the hysteretic behavior of RC circular bridge piers,twelve specimen piers was tested under cyclic combined flexural and torsional loadings,and then the effects of bending-torsion action on torsion and flexural capacity of RC bridge piers are evaluated. Based on the observed and measured results of damage characteristics and load-displacement relationship of tested specimens,the hysteretic restoring force models are developed to predict the responses of RC bridge pier under combined flexural and torsional loadings. The result shows that the flexural and torsional capacity may be impaired due to the effect of bending-torsion action,the failure modes and deformation characteristics are changed,and the damage zone tends to move upwards form the typical flexural plastic hinge zone due to the effect of additional torsional moment. The proposed empirical flexural and torsional hysteretic model for circular RC bridge piers with single spiral stirrup can very well predict the hysteretic behavior of circular RC bridge piers under combined flexural and torsional loadings.