High-Strength Steel Reinforcement (ASTM A1035/A1035M Grade 690): State-of-the-Art Review
Saif Aldabagh, M. Shahria Alam
Abstract
High-strength steel (HSS) and ASTM A1035 Grade 690, in particular, have been gaining popularity in the last two decades due to its considerably higher strength and corrosion resistance compared to conventional steel, i.e. ASTM A615 Grade 420. The stress-strain response of HSS is different from that of conventional Grade 420 steel because it lacks a well-defined yield point and yield plateau. Consequently, extensive research studies have been carried out to evaluate the performance of HSS reinforcement in structural concrete to examine the adequacy of current design provisions when a design yield strength of up to 690 MPa is used. In order to accommodate HSS reinforcement, the American Concrete Institute (ACI) released Design Guide for the Use of ASTM A1035/A1035M Grade 100 (690) Steel Bars for Structural Concrete (ACI 439.6R), whereas the AASHTO LRFD Bridge Design Specifications initiated the National Cooperative Highway Research Program (NCHRP) Project 12-77 to evaluate the provisions relevant to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernable yield plateau. This manuscript provides a synthesis of these two reports in a systematic way along with the other relevant research works. In addition, a comprehensive comparison between the requirements of ACI 439.6R, AASHTO, and ACI 318, relevant to the use of HSS reinforcement, is presented. Specified yield strengths for HSS, when used in different applications set by the three codes, are provided in a summary table. The provided table is intended not only for comparison purposes but also to facilitate the use of HSS reinforcement by designers because it contains all of the important and most recent relevant clauses in the three codes. Lastly, future research recommendations are proposed to revise and increase the specified yield strength of HSS in certain applications to enable designers to take full advantage of the potential benefits of HSS reinforcements.