Strength and Serviceability Performance of Large-Scale Deep Beams: Effect of Transverse Reinforcement

Past research programs investigating the shear strength of reinforced concrete deep beams lack a consensus on the effect of transverse reinforcement on the ultimate shear strength of reinforced concrete deep beams. Pertinent data regarding the serviceability performance of deep beams is also largely absent from past research studies. In addition, the overwhelming majority of test specimens in historical research studies are significantly smaller than the large-scale deep beams often utilized in practice.

To investigate the shear strength and serviceability performance of large-scale deep beams, a research study funded by the Texas Department of Transportation was conducted at the University of Texas at Austin. The objective of the study was to study the effect of the amount and detailing of transverse reinforcement and bearing area on the strength and serviceability performance of large-scale deep beam specimens. In addition, strut-and-tie modeling was evaluated in terms of its ability to provide both a conservative estimate of ultimate strength and address issues of serviceability in the specimens.

The experimental program consisted of nine tests on three large-scale deep beam specimens. The specimens are the largest specimens with shear reinforcement reported in shear research literature. It was found that the amount and detailing of transverse reinforcement and bearing area had only a marginal effect on the strength and serviceability performance of deep beams. In addition, the amount of transverse reinforcement had no effect on the first diagonal cracking load, but a large amount of transverse reinforcement was effective at reducing crack widths. It was also found that AASHTO LRFD, TxDOT 4371, and ACI 318 Appendix A strut-and-tie modeling provisions each provided conservative estimates of strength in the specimens. However,the strut-and-tie modeling provisions of ACI 318 Appendix A were not adequate from a standpoint of serviceability, if the formation of diagonal cracks under service loads is not desired.