Experimental verification of ACI 318 strut-and-tie method for design of deep beams without web reinforcement

This article presents an experimental investigation on 11 reinforced concrete (RC) deep beams without web reinforcement. Shear spandepth 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.