应变率效应对再生混凝土动态力学性能的影响

Influence of Strain Rate Effect on Mechanical Behavior of Recycled Aggregate Concrete

摘要:

通过约束再生混凝土单轴受压动态力学试验，研究了应变率效应对约束再生混凝土力学参数的影响.分析不同应变率下再生混凝土动态破坏特征以及受压应力应变关系全曲线，可以发现：在不同应变率、再生粗骨料取代率或体积配箍率下，再生混凝土单轴应力应变关系曲线的上升段基本一致，而下降段差异较为明显；随着应变率的提高或再生粗骨料取代率的增加，下降段曲线随之变陡，而随着箍筋配箍率的提高，下降段曲线明显随之趋于平缓.通过试验数据回归分析，提出约束再生混凝土受压峰值应力和峰值应变动态放大系数函数模型；随着应变率的提高，约束再生混凝土受压峰值应力和峰值应变均随之增大；而约束再生混凝土受压峰值应变动态放大系数增加幅值低于受压峰值应力动态放大系数的增加幅值；进一步分析了应变率效应对约束再生混凝土初始弹性模量的影响规律，确定了初始弹性模量和应变率的函数关系，并给出了初始弹性模量动态放大系数函数模型.随着应变率的提高，约束再生混凝土初始弹性模量动态放大系数随之增大，但其增长幅度要比受压峰值应力和峰值应变动态放大系数的增长幅度小.

关键词:再生混凝土; 约束; 动态试验; 应变率效应; 力学性能; 动态放大系数

Abstract:

Based on uniaxial compressive dynamic mechanical experimental tests of confined recycled aggregate concrete (CRAC), the influence of strain rate effect on mechanical performance of CRAC was comprehensively investigated. The dynamic failure pattern and the experimental complete curves of uniaxial compressive stressstrain of RAC subjected to dynamic loading with different strain rates were analyzed. It is found that for the uniaxial CRAC curves of strainstrain relationship, at various strain rates, replacement ratios of recycled coarse aggregate (RCA) or volume stirrup ratios, the feature of the ascending branch is basically consistent. However, the descending branch exhibits some differences. With the increase of the strain rate or the replacement ratio of RCA, the descending branch changes in a steepening trend. However, with the increase of the volume stirrup ratio, the descending branch changes obviously in a flattening trend. Through regression analysis of experimental test data, models of the dynamic increase factor (DIF) for the compressive peak stress and the peak strain were proposed, respectively. With increasing amplitude of strain rate, the compressive peak stress and peak strain of CRAC increases. However, the increasing trend of DIF for the compressive peak strain is smaller than that of the compressive peak stress. The influence of strain rate on the initial elastic modulus of CRAC was also investigated, and the relationship between the initial elastic modulus and the strain rate was determined based on the experimental data. Furthermore, the model of the DIF of the initial elastic modulus of CRAC was established. It is concluded that the DIF of the initial elastic modulus of CRAC increases at dynamic loading with increasing amplitude of strain rate, however, the increasing trend is smaller than that of the compressive peak stress, as well as that of the compressive peak strain.

Key words:recycled aggregate concrete; confined; dynamic tests; strain rate effect; mechanical behavior; dynamic increase factor