Effect of Fiber Reinforced Concrete in Members with Highly Complex Stress Fields

Abstract

Reinforced concrete (RC) members with significant geometric discontinuities and complex stress distributions under loading require considerable analyses and usually complicated reinforcement detailing. RC members with large openings are one of the examples. These large openings may interrupt the load transfer by direct concrete struts and cause substantial decrease in strength and unpredictable failure modes. The reinforcement detailing of these concrete members based on strut-and-tie models (STMs) is generally complicated and very often, these models cannot predict the failure mechanism due to localized damages. The actual stress fields in such members are typically very different from that predicated by STMs, as evidenced by many experimental investigations. This study investigates the performance of steel fiber reinforced concrete (SFRC) deep beams with multiple large openings under monotonically increased load. A simple design approach based on elastic finite element analysis (FEA) was used for the reinforcement detailing of the SFRC specimen. Experimental results indicated that, although the complex reinforcement detailing as per STM was not used, the SFRC specimen with 1.5% volume fraction of fibers reached much higher strength than the design load and exhibited ductile mode of failure.