Effects of Strain Rate on the Seismic Behavior of All‐Steel Buckling‐Restrained Braces

ABSTRACT Buckling‐restrained braces (BRBs) in buildings are intended to protect the primary structure from seismic damage by dissipating earthquake input energy through plastic deformation of their steel cores. To maximize the energy dissipation, they are supposed to sustain large strain amplitudes, which also correspond to strain rates much higher than those experienced by the primary structural components under the dynamic excitation of earthquakes. Most of the cumulative plastic energy in the encased steel core plate converts to heat that accumulates to give rise to the steel core and the unbonding medium attached to it. To investigate the effects of strain rate during dynamic loading, this paper introduces an experimental campaign of twelve geometrically identical BRBs subjected to uniaxial cyclic loadings at various levels of strain amplitudes and strain rates until the core plates fractured. Specifically‐designed assembled all‐steel BRBs were used to ease the visual inspection of the core plates and the temperature monitoring during the loading. The results show that the moderate strain rates of 3.0%s −1 to 18.6%s 1 had obvious effects on several important performance measures of the BRB specimens. They include the complicated variation in the peak forces, increased compression overstrength, and reduced cumulative plastic deformation capacities. Neglecting these effects may results in non‐conservative design of BRBs.