Influence of High-Strength Reinforcing Bars on Seismic Safety of Concrete Frames

High-strength longitudinal reinforcement can benefit the constructability and economy of concrete structures but concerns regarding the ductility and fatigue resistance have delayed its applications for seismic design. To evaluate the influence of reinforcement fracture on building seismic safety, a new damage model is developed using available data from reinforcement and member tests, and is employed with nonlinear dynamic analyses to assess and compare the seismic performance of concrete special moment frames with Grade 80 and 100 bars to frames with Grade 60 bars. The bar fracture and structural collapse risks are shown to depend on the bar yield strength, tensile-to-yield strength ratio (T/Y), and bar slenderness (s/d(b)) between lateral ties. Frames with Grade 80 and 100 bars (T/Y >= 1.2; s/d(b) <= 5) have comparable performance to frames with Grade 60 bars, where bar fracture probabilities are less than approximately 10% in frames (with maximum story drift ratios up to 0.04).