Bond strength of ASTM A 1035 Grade 100 reinforcing steel

The bond strength of ASTM A 1035 Grade 100 deformed reinforcing steel is evaluated relative to the values predicted using the development expressions in ACI 318-05 and ACI 408R-03. A total of 69 large-scale beam-splice specimens were tested at the University of Kansas, North Carolina State University, and the University of Texas at Austin, of which 64 failed in bond. Specimens contained bottom-cast lap-splices of No. 5, No. 8, and No. 11 Grade 100 reinforcement and were tested in four-point bending to provide a constant moment over the length of the splices. Parameters known to effect bond strength that were varied between specimens include the splice length, bar size, concrete covers and spacing, concrete compressive strength, and the amount of confining transverse reinforcement.; Lap splices developed bar stresses varying from 68 ksi to 155 ksi prior to splitting bond failure. Analysis of the results indicates that the ACI 318-05 development expression is unconservative. The inclusion of a high strength reinforcement factor psih = 1.48 is recommended for use with Grade 100 steel above 80 ksi bar stress. The ACI 408R-03 development expression with &phis; = 0.82 is conservative for use with Grade 100 steel. Both development expressions underestimate the contribution to bond strength of confining transverse reinforcement.; Keywords: ASTM A 1035; bond; confinement; deformed reinforcement; development; Grade 100; lap connections; reinforced concrete; splice; structural engineering.