Title: Experimental Verification of ACI 318 Strut-and-Tie Method for Design of Deep Beams without Web Reinforcement

Author(s): R. Kondalraj and G. Appa Rao

Publication: Structural Journal

Volume: 118

Issue: 1

Appears on pages(s): 139-152

Keywords: deep beam; shear span-to-depth ratio; strut efficiency; strut-and- tie model

DOI: 10.14359/51728083

Date: 1/1/2021

Abstract:
This article presents an experimental investigation on 11 reinforced concrete (RC) deep beams without web reinforcement. Shear span depth ratio (a/d), beam depth, and percentage of tension reinforcement are the variables. Beams with a/d less than 1.5 could carry loads beyond the diagonal cracking of concrete due to the formation of a diagonal concrete strut. Diagonal cracking of deep beams with an a/d of 1.0 was observed at a load of approximately 20% of ultimate capacity. Further, 607 more RC deep beam experimental results were collected from the literature. Strut-and-tie model provisions of ACI 318-14 and ACI 318-19 were validated with a database of 618 RC deep beam results. The capacity of beams with a/d higher than 1.5, and concrete strengths higher than 60 MPa was overestimated by ACI 318-19 even after the reduction of strut efficiency factor from 0.6 to 0.4. However, the percentage overestimation by ACI 318-19 is within 5.0%. ACI 318-14 predicts the capacity more accurately than ACI 318-19 with a strut efficiency factor of 0.6, with only 6.0% of overestimation, if the maximum shear strength limit is considered. The maximum shear strength limit of ACI 318-14 is found to be highly conservative. The reduction of strut efficiency factor in ACI 318-19 without modifying maximum shear strength limit results in highly conservative estimations.