Stress changes in reinforced concrete members due to creep

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Virginia Polytechnic Institute

Under sustained loads plain concrete and concrete members experience the phenomenon known as creep. Creep varies in rate and magnitude depending upon the nature and magnitude of load and upon the physical characteristics of the concrete. From a review of the literature, creep coefficients are studied as to how the values are affected by mixes, loadings, time, curing, and quality of aggregates and materials.

Within the allowable working stress range of concrete, creep strain can be considered proportional to the induced stress. Assuming known stress - creep strain - time relations, a series of equations have been derived analytically to calculate the stress changes in both the steel and concrete in reinforced concrete beams of rectangular cross-section due to creep relaxation. The data has been tabulated and graphed. Extensive use of the digital computer has been made to thoroughly investigate these stress changes within a wide range of parameters including these stress changes within a wide range of parameters including magnitude of load, strength of concrete, geometric proportion of the beams, and the amount and type of reinforcing steel.