正常使用状态下RUHTCC梁的弯曲变形预测

PREDICTION ON FLEXURAL DEFLECTION OF RUHTCC BEAM UNDER SERVICE CONDITION

该文以有效截面惯性矩为参数,提出了正常使用状态下钢筋增强超高韧性水泥基复合材料(RUHTCC)梁的挠度简化计算方法。与钢筋混凝土梁不同,RUHTCC梁需要考虑受拉区UHTCC在弯曲开裂后的承载能力,理论分析表明基于拉压区面积矩平衡与基于内力平衡且假定压应力线性分布所得的中和轴高度计算公式不同,而后者符合中和轴的物理意义。采用UHTCC的非线性拉、压本构模型以及受压区边缘压应变对应的割线模量,得到基于内力平衡的RUHTCC梁完全开裂截面的中和轴高度以及惯性矩公式。其次,有效惯性矩公式中的常系数m修正为随配筋率变化的函数,得到适用于RUHTCC梁的有效惯性矩公式。采用该文提出的挠度简化计算方法,对比预测与实测的屈服前荷载-挠度曲线,两者基本一致。

This paper presents a simplified method for predicting the deflection of reinforced ultra-high toughness cementitious composite(RUHTCC) beam under the service state, based on the parameter of the effective inertia moment of cross section. Different from reinforced concrete beam, the tension capacity of UHTCC in tension zone cannot be ignored. The theoretical analysis further indicates that the neutral axis obtained based on the equilibrium of area moment is different from that calculated from equilibrium of internal force with the assumption of linear distribution of compressive stress, while the latter accords with the physical meaning of neutral axis. By taking into account the nonlinear tensile and compressive constitutive models and the secant modulus corresponding to the strain of the extreme compressive fiber, the equations for neutral axis depth and inertia moment of full cracked section are obtained based on the equilibrium of internal force. Furthermore, for RUHTCC beam, the coefficient m in equation for effective inertia moment of section is revised to be a function with the parameter of longitudinal reinforcement ratio. The predicted load-deflection curve before yielding based on the proposed simplified calculation method shows good consistence with the experimental results.