Strain and bond stress distributions in tension lap joints in reinforced concrete

Fifteen reinforced concrete tension specimens were tested, each reinforced with a pair of lapped rods. Longitudinal reinforcement strain distributuions were measured using electrical resistance strain gauges installed within the reinforcement, and strain concentration gauges were used to obtain very detailed information at the ends of some rods. Thirteen of the specimens were loaded incrementally to study short-term effects and the other two were used for a preliminary investigation of sustained loadings. Results show the changing nature of the strain distributions, first as transverse cracks were developed and subsequently as lap failure was approached. The test results have been compared with the theoretical work of Tepfers. Peak and mean bond stresses at the formation of each crack were calculated and compared and bond stress distributions at lap failure are discussed.