Influence of Random Cracks on the Shear Behavior of Reinforced Concrete Beams Containing Steel Fibers

Abstract

The present study is aimed at investigating the influence of random cracks on the shear behavior of RC beams with steel fibers. For this purpose, several amounts of expansion agent and two percentages of steel fibers were used. From the strain history during the curing period of time, some sort of chemical prestress could be observed due to the use of expansion agent. Random cracks were successfully created and the pattern showed different crack densities, defined as the ratio between the area of the cracks and the uncracked area of concrete, for each beam. In some cases, a significant increase in the peak load was observed. In other cases only the deformability of beams was improved due to the addition of steel fibers.

Shear Behavior of Doubly Reinforced Concrete Beams With and Without Steel Fibers Affected by Distributed Cracks

“…Because ASR induced cracking takes a lot of time and special conditions to develop, the use of an expansion agent came as an alternative to have extensive cracking in a short period of time. From the results of previous research work 8) it was concluded that using expansion agents to generate distributed cracks in RC beams leads to a crack pattern similar to those obtained in actual structures 9) . The present study will further investigate the similarities between the two crack patterns.…”

“…Being randomly distributed throughout the concrete mass, steel fibers can better control the cracking in any direction. Adding short fibers to the concrete mix has several benefic effects ranging from reducing the crack opening 8) to an increase in the deformability and shear carrying capacity of RC beams 10), 11) .…”

“…The beams were designed to fail in shear and had a longitudinal reinforcement ratio of p w = 3.29%, for tension reinforcement, and a shear span to effective depth ratio a/d = 2.71. According to the reinforcement layout used in previous research 8) the influence of the chemical prestressing was quite important. A different reinforcement layout is adopted in the present study.…”

“…The notation of the specimens and mix proportions is kept similar to the one used in the previous reasearch 8) with the difference that a "DL" suffix was added to the names. This is to denote that the beams are doubly reinforced.…”

“…Prior to testing, the surface of the beams was inspected for the presence of distributed cracks. The crack density parameter introduced in the earlier research work 8) was used to mathematically quantify the influence of the distributed cracks on the shear carrying capacity of the beams. The beams exhibited a mixed mode of failure between both diagonal tension and diagonal compression failures.…”