Reinforcing struts and ties in concrete corbels

Abstract

This paper suggests a new perspective on reinforcement details for concrete corbels, whereby the familiar approach of secondary distributed reinforcement is substituted with modeling the corbel as a strut-and-tie system, in agreement with ACI 318 on strut-and-tie modeling (STM). The study consists of constructing and testing 15 corbel specimens until failure, including six conventionally reinforced reference specimens and nine proposed specimens in which only struts and ties were reinforced. The shear span-effective depth ratio (a/d) is variable: 0.5, 1, and 1.5, respectively. The test results show crack and strain evolution in both concrete and steel bars, together with load-deflection response. Conclusions show that corbel designs based on a strut-and-tie system provide substantial saving in weight of approximately 13 to 52% along with a less obvious but still substantial extra ultimate capacity of 12 to 50% compared to the nominal ACI 318-14 STM design load.