Feasibility of ACI 318-14 Strut-and-Tie Provisions for the Analysis and Design of Rubcrete and Steel Fibre Reinforced Rubcrete Deep Beams

Abstract

The regions in a structure with linear strain distribution are generally called as Bernoulli’s region (B-region) while the regions with nonlinear strain distribution are called Disturbed region (D-region). Most commonly used theories for the analysis and design of concrete structures are applicable only for B-regions since they are based on the assumption of linear strain distribution. This compels the structural designers to depend on empirical relations and thumb rules for the analysis and design of D-regions. Strut-and-Tie method is a newly developed design methodology that has the potential to analyse and design D-regions as well as B-regions with equal importance. The primary factor that influences the effectiveness of Strut-and-Tie method is the strut efficiency factor (βs). Even though Strut-and-Tie method is included in many of the International Standards like American code ACI-318-14, Canadian code CSA-A23.3-14, Australian code AS 3600-2009, Euro code EC2:2004, New Zealand code NZE 3101-1-2006, etc. the mentioned procedure is applicable only for conventional reinforced concrete. The paper highlights the development of strut efficiency factor (βs) for bottle-shaped strut in concrete deep beams (a D-region) with and without crumb rubber and steel fibre based on experimental and numerical studies. The obtained value of strut efficiency factor is used to check the feasibility of using the available value of βs for calculating the strength of concrete struts cast using rubcrete and steel fibre reinforced rubcrete (SFRR). Initially, the proposed method of analysis was validated using available experimental results. Good agreement was observed between the experimental failure load and deflection and that produced from numerical analysis.