Use Of Steel Fiber Reinforced Concrete In Structural 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 influence of highly complex stresses on the mechanical behavior of deep beams. One RC and three steel fiber reinforced concrete (SFRC) deep beams with two large openings were monotonically loaded up to failure. A simple design approach based on elastic finite element analysis (FEA) was also proposed for the reinforcement detailing of the SFRC specimens. Experimental results indicated that, although the complex reinforcement detailing as per STM was not used, the SFRC specimens with 1.5% and 1% volume fraction of steel fibers reached much higher strength than the design load and exhibited ductile mode of failure.