Experiments with Concrete in Torsion

Torsional stresses are developed in a structural member if it is subjected to the action of couples that lie in planes perpendicular to its axis. In the ordinary building frame, provision seldom is made for taking care of stresses of this nature, and current literature on the design of reinforced concrete structures contains little on the subject. The attitude of the designing engineer is to avoid torsional stresses rather than to take them into account; and as a rule they can be avoided quite successfully.

There are, nevertheless, a number of types of structural members in which twisting forces occur and such forces should not be left to take care of themselves. The most important case is that of longitudinal balcony girders that support cantilever beams. Exterior floor-beams will develop torsional stresses due to the deflection of adjacent loaded panels. A skew arch submitted to vertical load and a rigid-frame portal sustaining a horizontal wind pressure also, present problems in torsional resistance of reinforced concrete. This paper deals with the general behavior in torsion of plain and reinforced concrete; its resistance against failure; and various types of reinforcement that will increase its ultimate torsional strength.