As buildings get taller, bigger, and are required to resist higher seismic forces, the amount of reinforcement needed becomes impractical. Even if theoretical sizes can be calculated, it may be impossible to construct tightly spaced rebar cages or congested joint connections. Using higher strength reinforcement is a natural solution to this problem. Research on the use of high-strength reinforcement (HSR) began in the late 1950s. The outcome of this research first appeared in ACI 318-71, Building Code Requirements for Structural Concrete, which allowed limited use of reinforcement with a higher grade than 60 ksi. …