Use of High-Strength Reinforcement for Earthquake-Resistant Concrete Structures

Abstract

In the U.S., the specified yield strength of primary reinforcement of special concrete moment frames and special concrete shear walls may not exceed 60 ksi. As part of the Applied Technology Council ATC-98 Project, the use of high-strength reinforcement as primary reinforcement for seismic-force-resisting systems (SFRS) was studied. The purpose of the project was to examine the feasibility of using specified yield strength greater than 60 ksi and if so to recommend changes in design requirements and to reinforcing steel specifications. The use of ASTM A706 Grade 80 was specifically examined, and it was determined that Grade 80 reinforcement could be used with little change to ACI 318. It was also found that additional research is needed before a complete set of recommendations for use of reinforcement Grades 100 and 120 are made. This paper highlights the main findings and recommendations of the ATC-98 project. In particular, this paper discusses (i) desirable mechanical properties for highstrength reinforcing steel, (ii) the deformation capacity of concrete members reinforced with high-strength longitudinal reinforcement, (iii) minimum depths of interior beam-column joints in special moment frames, (iv) spacing of the transverse reinforcement to delay buckling of the longitudinal reinforcement, and (v) requirements for detailing lap-spliced bars.