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Abstract

Abstract
This investigation examines experimentally the behavior and ultimate strength of L-shaped reinforced high strength concrete beams under combined shear, bending and torsion.
The experimental program consists of casting and testing (13) high strength concrete beams under bending, shear and torsion. The main parameters are the effect of compressive strength, the eccentricity and transverse to longitudinal reinforcement ratio.
An increase in transverse to longitudinal reinforcement ratio by (21.43%) for beams under 80mm eccentricity of loading causes decrease in ultimate resisting torsional moment by (13.19%), and for an eccentricity of 170mm; the decrease in resisting torsional moment is (15.14%). Increasing in eccentricity for torsion of (112.5%) caused a decrease in load carry capacity by (43.33%) if all types of reinforcement remain the same.
By using multiple nonlinear stepwise regression analysis, based on data in this research and from other literatures; equations are proposed for predicting shear strength at cracking and ultimate loads and torsional capacity at cracking and ultimate loads. These proposed equations showed good agreement when compared with equations given by Codes of practice like (ACI, Canadian and BS) and showed good relations..

Keywords: Bending, high strength concrete, L-shaped beams, shear, torsion.

Keywords