Use of Steel Fiber Reinforced Concrete for Enhanced Performance of Deep Beams with Large Openings

Abstract

Reinforced concrete deep beams are used as primary load distribution elements in various civil engineering structures. Large openings often interrupt the load transfer by concrete struts in these beams and cause a sharp decrease in strength and serviceability. Although the strength evaluation and reinforcement details around the openings are essential considerations, the ACI Building Code does not provide explicit guidance for designing these elements with openings. Strut-and-tie models are commonly used for strength evaluation and design of deep beams with openings. However, reinforcement detailing based on these models can be very complex and the failure of deep beams may be due to localized damages that could not be predicted by the strut-and-tie models. In this study, an experimental investigation was conducted on two concrete deep beam specimens with large single opening, namely, reinforced concrete (RC) and steel fiber reinforced concrete (SFRC), to evaluate their performance under monotonically increased load. The reinforcement detailing in the SFRC specimen was considerably reduced since the steel reinforcement bars were only used for the tensile longitudinal reinforcements and the boundary elements. Both test specimens had significantly higher strength than the designed load computed based on one assumed strut-and-tie model.