Experimental investigation of shear models for lightweight aggregate concrete deep beams

The strut-and-tie model has become an effective design methodology for deep beams replacing the conventional beam theory that does not apply to these members due to their geometric or static stress discontinuities. This article examines the applicability of shear models for deep beams with lightweight aggregate concrete. Eight lightweight aggregate concrete deep beams were constructed and tested to failure under concentrated loading. Tests were conducted to investigate the effects of shear span-to-effective depth ratio (a/d), ranging from 0.26 to 1.04, and an effective span–depth ratio (le/h), ranging from 2 to 3, on the failure mode and shear behavior of deep beams. All specimens presented a shear compression or shear-flexure failure mode. Failure from the flexure mode showed a dominant pattern with increasing a/d. The le/h value minimally influenced the diagonal cracking and ultimate strength of deep beams. In contrast, a/d significantly affected the beam strength. Our results were compared with predictions proposed by American Concrete Institute 318-14, Canadian Standard, EC2, the Tan and Cheng model, the softened strut-and-tie model, and the simplified softened strut-and-tie model, which are all based on the strut-and-tie model. These comparisons indicated that all of these shear methods can be used to predict the shear strength of lightweight aggregate concrete deep beams