Taweep Chaisomphob, Suapphong Kritsanawonghong and Chayanon Hansapinyo

pp. 41 - 52

Abstract

This paper presents the experimental investigation on the failure mechanism and ultimate capacity
of rectangular reinforced concrete beam under combined action of bi-axial shear accompanied with torsion
through the test of four reinforced concrete members. The simple experimental set-up for a simply-supported
beam under one point loading is introduced in this study by applying eccentric load to the tilted beam.
This requires only one hydraulic jack to produce the complicated bi-axial shear and torsional loading. The
main parameter is the magnitude of torsion induced to specimens which is relatively represented by the
torsion-to-shear ratio. In addition, the influence of torsion on ultimate capacity of reinforced concrete with
different ratio of two shears is investigated. From the experimental results, it is found that the increase in
the magnitude of torsion about 69 percent drastically decreases bi-axial shear capacity as much as 12 to 39
percent according to the ratio of bi-axial shears. The experimental results are compared with the capacities
calculated by the available interaction formula between uni-axial shear and torsion in the current design codes. The comparison indicates that the current design codes give quite conservative values of ultimate
capacity.

Keywords

• reinforced concrete beams
• bi-axial shear and torsion
• ultimate capacity