Bond in Flexural Members with Plain Steel Reinforcement

Abstract

Two concrete T-beams reinforced with instrumented built-up hollow plain bars were tested to investigate the effect of flexural cracking and bond loss on the flexural and shear behavior. The beam with a flexural reinforcement ratio of 0.98% exhibited arch action due to bond failure that initiated when the applied load reached 60% of the failure load. The beam with a reinforcement ratio of 0.33% exhibited predominantly beam action until failure initiated by yielding of the longitudinal reinforcement. When beam action was the primary shear-carrying mechanism, the observed bond demand was greatest within the transition zone between elastic-uncracked and elastic-cracked behavior. The transition from beam action to arch action caused a marked reduction offlexural stiffness that indicated bond loss in beams with plain reinforcement.