Time-dependent behavior of bond between reinforcement and concrete

1.确定荷载作用下混凝土与变形钢筋的粘结应力-滑移关系：(1)基于棱镜试验结果，研究并模拟了持续荷载作用下混凝土与变形钢筋之间的粘结应力-滑移关系。(2)利用粘结应力-滑移模型分析了柱体中钢筋应变分布和附加端部滑移的时变特性。钢筋混凝土悬臂梁在持续荷载作用下固定边钢筋滑移引起的附加挠度：(1)给出了不同端部弯矩作用下杆件的粘结分析方程。分析采用了第一部分提出的粘结应力与滑移关系的模型，通过粘结分析计算了钢筋滑移引起的裂缝宽度和挠度。(2)混凝土端部滑移的增加主要由混凝土的收缩决定，而钢筋应力的大小对端部滑移的增加几乎没有影响。(3)在持续加载的一天内，悬臂梁的挠度显著增加。考虑混凝土在持续荷载和徐变收缩作用下粘结应力与滑移关系的变化，充分、准确地分析了张拉棱柱和悬臂梁的时变行为。通过粘结分析得到了长期裂缝宽度的计算公式：方程中考虑了受压混凝土徐变、混凝土粘结徐变和裂缝间收缩引起的附加裂缝宽度。

1. Relationship of bond stress-slip between concrete and deformed bar under susutained loading :(1) The relationships between the bond stress and the slip under sustained loading were investigated and modeled based on the result of the prism tests.(2) Time dependent behavior of the distribution of the steel strain and the additional end slips of steels in the prisms were analyzed by using the bond stress-slip model.2. Additional deflection in reinforced concrete contilever beams due to slippage of bar at fixed edge under sustained loading :(1) Bond analysis equations for members on which defferent end bending moment acts were also presented. The analysis used the model of the relationships between bond stress and slip proposed in the part 1. Crack widths and deflections that occured by the slippage of steel were calculated by the bond analysis.(2) The increase in end slip was dominated by shrinkage of concrete and was scarcely influenced by the magnitude of steel stress.(3) The deflection in the cantilever beams increased remarkably within one day of sustained loading. The long-term deflection was influenced significantly by the end slip of steel.(4) Time-dependent behavior of the tension prisms and the cantilever beams was analyzed sufficiently and accurately by considering the change in the relationship between bond stress and slip under sustained loading and creep and shrinkage of concrete.3. A equation of long-term crack width was obtained by the bond analisys : A additional crack width due to creep of compressive concrete, bond creep and shrinkage of concrete between cracks was considered in the equation.