Bond Behavior of Grade 100 ASTM A 1035 Reinforcing Steel in Beam-Splice Specimens

Abstract

The bond behavior of Grade 100 ASTM A 1035 deformed steel reinforcing bars manufactured by MMFX Technologies Corp., operating at stresses from 80 to 140 ksi, is evaluated. The reinforcement is tested using beam-splice specimens designed to investigate factors known to influence bond behavior, including splice length, bar size, concrete cover, concrete compressive strength, and transverse reinforcement. The tests were performed as part of a joint bond research program conducted at the University of Kansas (KU), North Carolina State University (NCSU), and the University of Texas at Austin (UT). This report describes the tests performed at KU and summarizes the data from the three schools. Of 69 specimens tested, 64 failed in bond in the splice region. Lap splices developed bar stresses between 68 and 155 ksi prior to failure. The use of confining transverse reinforcement significantly increased splice strength and deformation capacity of the beam specimens. The development length equation proposed in ACI 408R-03 is an accurate predictor for the beam-splice specimens, with a coefficient of variation of test/prediction ratios of 0.11 for splices without confining transverse reinforcement, and 0.10 for those with confining transverse reinforcement. The development length equation in ACI 318-05 exhibited more scatter with respect to the test data than the ACI 408R-03 equation and significantly over predicted bar stress in splices without confining transverse reinforcement, indicating that it cannot be used for development length and splice design with Grade 100 reinforcing steel. A development length equation proposed by NCSU as part of this study provides an accurate representation of strength for splices without confining transverse reinforcement.