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

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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