Torque Capacity of U- and H-Shaped Reinforced Concrete Walls Using Warping-Equivalent Bending Moment

Hoult, Ryan [UCL] Saraiva Esteves Pacheco De Almeida, João [UCL]

Nonplanar reinforced concrete (RC) core walls form the backbone of millions of mid- and high-rise buildings, resisting both gravity and lateral loads from wind and earthquakes. The latter inevitably induces torsional demands, even in the case of full plan-wise symmetric structures, which add to bending, shear, and axial deformations. Unfortunately, current international building codes are not applicable for the design of nonplanar sections governed by warping torsion rather than circulatory torsion. This lack of information and guidance in building codes has resulted in a very limited number of structures being designed to account for warping stresses, even though the latter can be of a similar order of magnitude to bending stresses and, therefore, of major significance. A simple procedure is herein presented to estimate the ultimate warping moment and ultimate torque of nonplanar RC sections based on “warping-equivalent” ultimate bending moments from sectional analysis. A circular and bilinear bending moment-torque interaction relationship is proposed and compared to the existing, albeit limited, experimental and numerical results available in the literature.