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This paper presents a theoretical model for structural concrete in pure torsion which is comparable in rationality and generality to the well known theory for flexure. As in flexure the theory is formulated by considering the equilibrium conditions, the geometry of deformation, and the stress-strain characteristics of the steel and the concrete. The model is capable of predicting the complete post- cracking torsional behavior of symmetrically reinforced structural concrete members. In the paper the theory is applied to the following cases: the torsional response of reinforced and prestressed concrete members; the torsional capacity of under-reinforced, partially over-reinforced and completely over-reinforced members; and the prediction of balanced reinforcement ratios. [ABSTRACT FROM AUTHOR]

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This paper describes tests on the dowel action of steel crossing artificial cracks in reinforced con-crete. Theoretical relationships obtained by ana-lyzing the test results have been compared to the actual test values. [ABSTRACT FROM AUTHOR]

Bleeding can have far-reaching effects on the properties of concrete and it Is a phenomenon which has too often been ignored. This paper briefly discusses some of its important consequences with particular emphasis on tensile strength and deformational behavior, and suggests a method by which effects of bleeding on the internal structure of concrete may be studied. [ABSTRACT FROM AUTHOR]

A series of four tests were conducted on full size precast, prestressed concrete beam-column assemblies under reversed cyclic loading of high intensity. The test variables included the amount of transverse confining steel for ductility and the position of the plastic hinge in the members. It was concluded that large post-elastic deformations can be attained in prestressed concrete members and that the energy dissipation at large deforma-tions can be considerable, but only once the con-crete in the compression zone has commenced to crush and hence when structural damage has been incurred. [ABSTRACT FROM AUTHOR]

The strength, cracking, and deformation simili-tude of full, one-half, and one-third scale models of reinforced concrete T-beams without and with stirrups and failing in shear and flexure is reported. The effects of aggregate size and control speci-men size are also investigated. The greater deflections and the increased strength characteristics of models before failure is shown to be due to their increased strain capacity and the presence of a strain gradient in the com-pression zone. For strength and cracking similitude it is necessary to scale down the maximum aggre-gate size. One-third scale models consistently show larger increases in strength. Models made from the same materials as the prototype are able to satis-factorily simulate deformation and stiffness charac-teristics of the prototype. [ABSTRACT FROM AUTHOR]

The instantaneous deformations of a concrete under load are influenced considerably by the testing conditions and composition of concrete. The mechanism of such deformations can be explained in qualitative terms by the theory of internal crack propagation; for numerical approximation, however, only empirical formulas are available. Empirical formulas are also available for the estimation of the unit strain and the secant modulus of elasticity of concrete at the ultimate compressive stress. [ABSTRACT FROM AUTHOR]

The stress-strain relationship in compression of hydrated portland cement (with a water-cement ratio of 0.33) and a lightweight concrete was studied at elevated temperatures. The properties of both materials seemed to be virtually unaffected by temperature up to about 400 F. Above this, the modulus of elasticity and ultimate strength decreased with increasing temperature. These changes were more definite for hydrated portland cement. [ABSTRACT FROM AUTHOR]

An experimental investigation into the behavior of plain concrete under cyclic loading is described. Stress-strain curves obtained for concrete cylinders under such loading are presented, and analytical stress-strain relations for cyclic loading are derived. Assuming the property of uniqueness of stress-strain relations, it is shown how the cyclic stress-strain curves can be used to predict the behavior of a concrete fiber subjected to an arbitrary load history (neglecting creep). [ABSTRACT FROM AUTHOR]