箍筋约束再生混凝土受压本构关系及加载应变速率影响规律研究

Concrete is strain rate sensitive material, which exhibits different mechanical properties under such as static loading, earthquake, impact and explosive loading. Currently, there is scarce investigation on stress-strain curve of stirrup confined recycled concrete under compression, especially on effects of strain rates on its mechanical properties. In this program, stirrup confined and unconfined recycled concrete full-scale specimen are tested by a servo hydraulic testing machine with a capacity of 20000kN, which aims at studying the characteristic of stress strain curve at low strain rate (10-6/s) and high strain rate (10-3/s), respectively. Moreover, Split Hopkinson Pressure Bar is used to study the stress-strain behavior of recycled concrete under impact loading (at strain rates of 10/s~102/s). The study aims at establishing the constitutive model of stirrup confined and unconfined recycled concrete under a wide range of strain rates and revealing the effects of strain rates, which provides theoretical and experimental basis for applications of recycled concrete under different conditions and in different areas, such as industrial, civilian and military engineering.

混凝土为应变速率敏感材料，在静力荷载、地震作用、冲击和爆炸荷载作用下，呈现出不同的强度和变形特性。本项目针对箍筋约束再生混凝土受压本构模型及加载应变速率影响规律研究较少的现状，拟采用20000kN伺服液压试验机对足尺的箍筋约束再生混凝土试件、素再生混凝土试件进行不同应变速率加载，研究不同约束水平的箍筋约束再生混凝土在低应变速率（10-6/s）、高应变速率（10-3/s）下的受压本构曲线特征。此外，采用分离式霍普金森压杆对冲击荷载下（应变速率10/s~102/s）再生混凝土本构关系与动态特性进行研究。项目拟建立不同应变率下箍筋约束再生混凝土（包括素再生混凝土）的受压本构模型，同时揭示加载应变速率对全曲线特征的影响规律，为再生混凝土在不同工况、不同用途（工业、民用、军事工程）中应用提供理论与试验依据。

随着建筑业可持续发展与绿色环保的要求日益得到重视，再生混凝土的研究与应用成为热点。应力-应变本构关系是分析再生混凝土构件承载力和变形计算的依据，国内外对非约束再生混凝土在静力作用下的应力-应变本构关系有不少研究，但对约束再生混凝土应力-应变本构关系和动态应力-应变本构关系研究较少。本项目进行了102个足尺箍筋约束再生混凝土试件轴心受压试验，以及156个试样分离式霍普金森压杆冲击试验，获得箍筋约束再生混凝土应力-应变全曲线，以及不同应变率下再生混凝土动态应力-应变曲线，通过理论分析与数据拟合，提出了箍筋约束再生混凝土的单轴受压本构关系模型，揭示了应变率对再生混凝土弹性模量、峰值应力、峰值应变、极限应变等的影响规律。研究结果可为再生混凝土结构设计提供理论基础，具有工程应用价值。