Single-span deep beams subjected to unsymmetrical loads

This paper investigates the effects of unsymmetrical loadings on the strength and behavior of simply supported deep beams. An experimental program consisting of 14 specimens has been carried out. Test results including crack patterns, load-deflection responses, steel and concrete strains, and failure loads are presented and discussed with the effects of load inequality (LI) and load asymmetry (LA). Conclusions are drawn on the effects of LI and LA on deep beam behavior. The ACI 318-05 strut-and-tie method is found to slightly overestimate the beam shear capacity. The writers proposed a direct strut-and-tie method (STM) for predicting the failure loads of unsymmetrically loaded deep beams. By adopting an interactive failure criterion, no preset empirical stress limit is required in the model. A load parameter Π is introduced such that the proposed STM can simulate both the effects of LI and LA. It is shown that the proposed STM is a generalized form that embodies the special cases of single-point and two-equal-point symmetric loading conditions. Besides, the model gives promising results in predicting the possible failure modes. The STM predictions are in good agreement with test results as well as finite-element predictions of 14 specimens.