Influence of Height and Section Shape of Rectangular Confined Concrete on its Stress-Strain Relationship

在混凝土结构的最新性能设计中，结构构件的荷载变形特性和损伤评估信息是必不可少的。这种情况导致了对混凝土，特别是与构件结构性能密切相关的约束混凝土的应力-应变关系进行更多研究的必要性。研究了矩形截面混凝土在单轴压缩荷载、剪力和轴向荷载作用下的强度和变形特性。主要结论如下。(1)在素混凝土单轴受压情况下，矩形截面边长比对应力应变关系影响不大，但截面高度与短边长比对应力应变关系的影响显著，即强度处的抗压强度和应变增大，应力应变关系下降分支的梯度随着边长比的减小而减小。相反，在受约束混凝土的情况下，观察到高度与短边长度之比的类似显着影响。边长比对矩形截面的强度和变形性能产生影响，这是由于侧向钢筋的围应力相对于长边长的减小。2)推导了矩形截面不同长边长比、短边长比、高与短边长比下混凝土的应力-应变关系方程。结果表明，该方程能较好地预测结构的强度和变形特性。3)恒定剪切力和轴向荷载作用下约束混凝土的单轴应力-应变特性表现为切线模量较小，压缩较小。在剪切力水平较高的情况下，强度和应变较小。利用试验数据介绍了强度和应变的计算公式。少

For the latest performance design of concrete structures , information on load-deformation characteristics and damage assessment of structural members are required essentially. This situation leads to necessity of more researches, on stress-strain relations of concrete, especially confined concrete which relates closely structural performance of the members.Investigations on strength and deformation properties of the concrete with rectangular sections under uni-axial compression load, and subjected to shear force and axial load were carried out. Following main conclusions are obtained.1) In the case of plain concrete under uni-axial compression, though the side length ratio of rectangular section has little influence on the stress-strain relationship, the ratio of height to the short side length of the section has a pronounced effect on the characteristics, that is, compression strength and strain at the strength increase, and gradients of falling branch of stress-strain relations beco … More me more gently with decrease in the ratio. In contrast, in the case of confined concrete, similar remarkable effects of the ratio of height to the short side length are observed. The side length ratio influences strength and deformation properties due to decrement of confining stress of lateral reinforcement relative to long side length of the rectangular section.2) Equations to estimate stress-strain relations of concrete with different ratios of long side length, to short one, and ratios of height to short side length of rectangular sections are derived. Moreover, it is shown that the equations predict strength and deformation characteristics with practical accuracy.3) Uni-axial stress-strain characteristics of confined concrete subjected to constant shear force and axial load show smaller tangent modulus, smaller compressive. strength and smaller strain at the strength, in the case of higher shear force level. Equations to estimate strength and strain at the strength are introduced using test data. Less