Experimental study on the effects of bi-directional loading pattern on rectangular reinforced concrete walls

In this experimental study, three identical reinforced concrete (RC) walls were tested under three different lateral loading patterns. These loading patterns were cyclic in-plane, skewed with 45° angle and clover leaf. The main objective was to investigate the effects of these bi-directional loading patterns on the seismic behavior of slender rectangular RC walls. The results showed significant increase in tensile and compressive strains in concrete and longitudinal bars that led to earlier cover concrete spalling and bar buckling in the specimens subjected to bi-directional loading. The neutral axis depth and compression zone were found to be substantially larger when subjected to bi-directional loading and this led to the occurrence of concrete crushing and bar buckling in the web. Moreover, lateral instability failure triggered earlier in the specimens under bi-directional loading, as a result of reduction of out-of-plane stiffness of the wall. However, bi-directional loading did not significantly increase out-of-plane buckling of the wall in terms of out-of-plane displacement. In-plane and out-of-plane shear cracks formed in one of the specimens subjected to bi-directional loading, whereas the same wall under in-plane loading developed only flexural cracks. It was also found that in-plane shear deformation was larger when the wall was subjected to bi-directional loading. The results of this experimental study emphasize the need for further investigation of the effects of bi-directional loading on RC structural walls.