小跨高比钢筋混凝土连梁非线性剪切滞回和分析模型研究

HYSTERETIC SHEAR AND ANALYSIS MODELS FOR REINFORCED CONCRETE COUPLING BEAMS WITH SMALL SPAN-TO-DEPTH RATIOS

基于修正力插值的纤维单元(MFBFE)的力插值函数中加入剪力插值函数,从单元层次上考虑了弯矩和剪力的耦合作用,适合以剪切变形为控制因素的小跨高比连梁(跨高比小于2.5)的非线性数值模拟。本文从截面层次上建议了一种针对小跨高比连梁的剪切滞回模型,该模型抛弃了屈服剪力与峰值剪力相等的假设条件,其骨架曲线为四折线型,包括开裂点、屈服点、峰值点以及破坏点,卸载、再加载路径的变化以及捏缩效应由所建议的滞回规则体现。在OpenSees中单轴材料类开发这一剪切滞回模型(CBHShear),给出了OpenSees框架下MFBFE单元调用CBHShear材料的实现方式。最后基于MFBFE单元和CBHShear模型,对不同小跨高比、配筋率、配箍率、钢筋强度、混凝土强度的4个连梁试件进行低周反复加载数值分析,所得结果与试验结果进行对比,验证了CBHShear能够很好地体现连梁的非线性行为,具有较高地预测精度,适用范围更为广泛。

The force interpolation function of Modified Force-Based Fiber Element(MFBFE)contains shear force interpolation function,which is able to consider the interaction between the bending moment and the shear force at the element level.It is suitable for nonlinearly numerical simulation of coupling beams with small span-to-depth ratios(less than 2.5)governed by shear deformation.At the section level,a hysteretic shear model for coupling beams is proposed,without the assumption that the yield and maximum shear forces are equal.The envelope curve based on multi-linear model includes cracking,yielding,maximum,and failure points.Both unloading and reloading paths and pinching effect are exhibited by the proposed hysteresis rules.The code for MFBFE and the proposed hysteretic shear model called CBHShear have been implemented into OpenSees.4 specimens are simulated using the proposed analysis model,which have different small span-to-depth ratios,longitudinal reinforcement ratios,transverse reinforcement ratios,reinforcement strength and concrete strength The analytical results are compared with the test results,which show good agreement and verify that the model can accurately represent the nonlinear behaviors of various sizes of coupling beams.