13/07/2020
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. However, the maximum yield strength of reinforcement in elements resisting seismic loads was limited to 60 ksi. This restriction remained in the building code until recently due to a lack of data on cyclically loaded members with HSR. The main expected advantage of HSR over conventional reinforcement (CR) is a lower volume of reinforcement material in construction, resulting in lower construction time and costs. Now, the code has been revised to ACI 318-19 in July, 2019 and likely to be referenced in IBC 2021.
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(Data Source: Structure Magazine)
