Short-term deflections of reinforced concrete beams

TLDR: In this article, the flexural rigidity of reinforced concrete members is determined in the calculation of the deflection, and the results of tests carried out by the Cement & Concrete Assoc.

Abstract: The article examines the problem of determining the flexural rigidity EI in the calculation of the deflection of reinforced concrete members. It is shown that EI varies with the magnitude of bending moment due to the increasing propagation of cracks. Tests have shown that the difference between measured and calculated stresses in such members is due to the presence of cracks and the effect of the concrete between the cracks. So that a realistic prediction of deformation can be made, the tension stiffening effect of the concrete must be considered and specified in terms of strain reduction of the reinforcement due to the concrete action. The results of tests carried out by the Cement & Concrete Assoc, are used to evaluate factors expressing the efficiency of concrete in resisting tension and the average position of neutral axis. Graphs are given to compare test results with calculated deflection values. /TRRL/