Title: Influence of Web Reinforcement on Strength of Bottle- Shaped Strut in Concrete Deep Beams
Author(s): Mohammed K. Dhahir and Wissam Nadir
Publication: Structural Journal
Appears on pages(s): 223-232
Keywords: deep beams; shear strength; strut-and-tie model (STM); strut efficiency factor; web reinforcement
Deep beams are usually designed using strut-and-tie models (STMs), where loads are assumed to be transferred through an inclined bottle-shaped strut. Such a mechanism introduces high transverse tensile strain within the strut, thus reducing its effective strength considerably. To account for this phenomenon, current codes of practice apply a strength reduction factor to the strut and require providing minimum amount of web reinforcement. However, these reduction factors do not consider the effect of varying the amount of web reinforcement on the strength of the strut. In this paper, a previously proposed STM by the authors has been extended to include deep beams with web reinforcement. The proposed STM considers the effect of varying both the shear span-to-effective depth ratio (a/d) and the amount of web reinforcement on the efficiency factor of the inclined strut. Furthermore, the proposed STM also presents a simplified and economic design procedure of web reinforcement to resist a certain load. The accuracy of the proposed STM was verified using a database of 241 specimens that failed in shear. Based on the results, the proposed STM has yielded more consistent and accurate results when compared to the other STMs used in this study.