Bond Strength of ASTM A 1035 Grade 100 Reinforcing Steel

Abstract

The bond strength of ASTM A 1035 Grade 100 reinforcing steel is evaluated relative to the values predicted using the development expressions in ACI 318-05 and ACI 408R-03. Sixty-nine beam-splice specimens were tested at the University of Kansas, North Carolina State University, and the University of Texas, of which 64 failed in bond. Specimens contained bottom-cast lap-splices of No. 5, No. 8, and No. 11 Grade 100 reinforcement. Parameters studied include splice length, bar size, concrete compressive strength, cover, and the amount of confining transverse reinforcement. Lap splices developed bar stresses varying from 68 ksi to 155 ksi prior to splitting bond failure. Results indicate that the ACI 318-05 development expression is unconservative. Inclusion of a high strength reinforcement factor ψh = 1.48 is recommended for use with Grade 100 steel. The ACI 408R-03 development expression is conservative. Both expressions underestimate the contribution to bond strength of transverse reinforcement.