Analysis of non-prismatic concrete beams under pure torsion: Numerical study

Reinforced concrete non-prismatic beams are widely used in structural engineering. Reinforced concrete non-prismatic beams are preferred members for many applications due to their important advantages. These include bridge pier caps, long-span girder bridge, and building frames. Light weight is the major benefits of this form of the beam which allows a bigger span in comparison to prismatic members. Despite of these advantages, there are no specific recommendations provided by different codes that would insure the detailing of these elements. Members with significant torsion require complicated 3D stress analysis, particularly after the members have developed a few cracks in the earlier stages of loading leading to development of nonlinear and complicated response for the members. In the present study, a 3D analysis using finite element method has been made to study the behaviour of non-prismatic reinforced concrete beams under pure torsion. Validation of a results obtained by finite element was done through a comparison with experimental data with respect to cracking load, maximum load, and torque-twist curve. Longitudinal torsional reinforcement improves maximum capacity by about 28.6%. An increase in tapering angle by about 100% modified the torsional capacity by about 15%. Generally, the FE results matched experimental results within 8%.