动态单调荷载下约束再生混凝土单轴受压应力-应变全曲线方程

在MTS 815力学试验上，完成了81个箍筋约束再生混凝土短柱动态力学试验，分析约束再生混凝土在不同变率下的破坏特征。基于获得的应力-应变试验曲线，研究应变率效应、箍筋约束效应和再生粗骨料取代率对约束再生混凝土力学和变形性能的影响。根据应变率效应对约束再生混凝土力学和变形性能的影响规律，初步提出约束再生混凝土性能指标动态放大系数（DIF）模型。分析箍筋形式、箍筋间距、箍筋屈服强度和配箍率等因素对约束再生混凝土短柱力学行为的影响，初步提出约束再生混凝土性能指标约束放大系数（CIF）模型。分析表明，箍筋约束效应对再生混凝土的力学和变形性能有重要的影响，在很大程度上改善了再生混凝土的延性。研究再生粗骨料取代率对约束再生混凝土力学和变形性能的影响规律，提出取代率影响因子（RIF）模型。基于约束再生混凝土短柱动态试验数据分析，提出考虑应变率效应、箍筋约束效应和再生粗骨料取代率影响的约束再生混凝土应力-应变分析模型，定义受压应力-应变全曲线特征点参数，确定约束再生混凝土受压应力-应变全曲线方程。研究表明，应力-应变计算曲线和试验曲线吻合较好，验证了分析模型的合理性，为再生混凝土结构动力非线性分析和抗震优化设计提供研究基础。

Dynamic complete stress-strain curve equations of recycled aggregate concrete under monotonic uniaxial loading

The dynamic tests of 81 recycled aggregate concrete (RAC) short columns confined by transverse hoops were carried out at an MTS 815 testing machine. The failure modes of confined recycled aggregate concrete (CRAC) under various strain rates were thoroughly analyzed. Based on the obtained measured stress-strain curves, the influences of the strain rate effect, the confinement effect, and the replacement percentage of recycled coarse aggregate (RCA) on the mechanical and deformation performance of CRAC were investigated. According to the influence law of the strain rate on the mechanical and deformation performance of CRAC, the dynamic increase factor (DIF) model of the performance index for CRAC was initially proposed. The influences of those factors, such as the type of the transverse hoop reinforcement, the spacing of the hoop set, the yield strength of the hoop reinforcement, and the volume ratio of the stirrups on the mechanical behavior of the CRAC short column were deeply analyzed. The confining increase factor (CIF) model of the performance index for CRAC was also preliminarily developed. The analysis results indicate that the confinement effect of the hoop reinforcement has an important influence on the mechanical and deformation performance of CRAC, and the ductility of RAC is improved significantly. By analyzing the influence of the replacement percentage of RCA, the replacement ratio influence factor (RIF) model was suggested. Based on the dynamic tests of the CRAC test units, the analytical model of the stress-strain relation for CRAC was proposed by applying the factors of DIF, CIF, and RIF to the characteristic parameters. The corresponding complete stress-strain curve equations of CRAC are developed and determined. The analytical curves and the experimental curves agree well, which indicates that the proposed analytical model is reasonably good. The results provide a significant research foundation for the dynamic nonlinear analysis and seismic optimum design of RAC structures.