Bond and Anchorage of High-Strength Reinforcing Steel

Recent revisions to the AASHTO load and resistance factor design (LRFD) construction specifications permit the specification of ASTM A1035 reinforcing steel. ASTM A1035 reinforcing bars are low-carbon, chromium steel bars characterized by a high tensile strength and a stress–strain relationship having no yield plateau. The AASHTO LRFD bridge design specifications limit the yield strength of reinforcing steel that may be used in design to 75 ksi (520 MPa) for most applications. Therefore, although ASTM A1035 may be specified, the higher yield strength cannot be used in design. The objective of this work is to evaluate existing AASHTO LRFD bridge design specifications in reference to the use of high-strength reinforcement represented by ASTM A1035. Issues of bar splice development and hooked-bar anchorages of ASTM A1035 reinforcing steel are discussed. Four spliced-beam straight-bar development tests and 18 hooked-anchorage pullout tests were performed as proof tests of the current AASHTO requirements. The study clearly demonstrates that the current AASHTO and American Concrete Institute requirements for both straight-bar tension development and hooked-anchorage tension development may be extended to develop bar stresses of at least 125 ksi in up to 10-ksi concrete. The results of this study and previous work clearly indicate that confining reinforcement should always be used when ASTM A1035 reinforcing steel is developed, spliced, or anchored.