The effect of unequal load values on reinforced concrete deep beams

Abstract

One of the most important problems facing the behavior and strength of deep beams is the asymmetry of the load in terms of magnitude despite its presence in the center of the beam span. It is known that the compression paths (struts) that transfer the load from the support points to the load points are usually symmetrical in deep beams when the 2-point load is central and equal, but in the current research work these struts are asymmetrical as a result of the inequality of load. This led to the strut with the higher load failing before that with the lower load. Therefore, the deep beam fails early. Twelve deep beam specimens were analyzed using SAP2000 software, which is based on the finite element method. Unequal 2-point loads of 33%-67%, 25%-75%, and 12.5%-87.5% were adopted. This case was studied using different values of concrete's compressive strength of 20, 30, and 40 MPa. Accordingly, the load capacity, midspan deflection, positive moments, and shear stresses decreased by about 24-13%, 22-8%, 11-10%, and 15-13.5%, respectively.