Experimental study on reinforced concrete walls under combined flexure, shear and torsion

The test results of reinforcement concrete cantilever walls subjected to monotonic combined flexure, shear and torsion are presented. In particular, the effects of the torque to bending moment (T/M) ratio on the failure mechanisms, crack patterns, strength and stiffness are discussed. It is found that the torsional effect is able to induce finer crack distributions and hence more uniform damage. The flexural strength of the test walls is reduced by the increasing torque. On the other hand, the wall under relatively large T/M ratio is capable of sustaining almost equal torsional strength as the wall under pure torsion. For walls under combined loadings, degradations of both pre-cracking torsional stiffness and lateral stiffness are observed. In addition, the test results are compared with predictions by American Concrete Institute (ACI) provisions by evaluating the interaction diagrams between bending moment and torsion. It is found that the ACI provisions give very conservative predictions, especially for walls under pure torsion or dominant torsion.