Arch action in reinforced concrete beams - A rational prediction of shear strength

A rational expression, developed to predict the shear strength of reinforce d concrete beams, is derived from the relationship between shear and the ra te of change of bending moment along a bean coupled with experimental findi ngs for the arch action. Eight reinforced concrete simple span beams withou t web reinforcement were tested statically up to failure to investigate qua ntitatively the arch action. Variables included four shear span-to-depth ra tios (2, 2.5, 3, and 4) and two longitudinal steel ratios (1 and 2 percent) . On the basis of the experimental findings, an equation is proposed to pre dict the internal moment arm length, which then leads to a shear strength e quation that combines beam action and arch action. The proposed ultimate sh ear strength equation arising from analytical premises and then calibrated with experimental data, is a similar form to the ACI 318 equation derived m ainly from. an empirical approach. The proposed ultimate shear strength equ ation applied to existing test data and the results were compared with thos e predicted by the ACI 318 equation and the Zsutty's equation.