Nonlinear Time-History Analysis of Seismic Performance of RC Frames Equipped with Buckling-Restrained Braces Versus Viscous Fluid Dampers

Abstract

Buckling-restrained braces (BRBs) and viscous fluid dampers (FVDs) dissipate seismic energy through yielding hysteresis and velocity-dependent action, respectively. This paper takes a six-story reinforced concrete (RC) frame as the object, compares the seismic mitigation performance of the two types of devices under a common layout, and further investigates the structural responses of different layouts under near-fault ground motions. Wen-type BRB and Maxwell-type FVD models are established in ETABS 22 and verified against theoretical and published experimental results. The baseline analysis uses six horizontal components from three sets of ground motions (W1–W6), scaled to frequent (0.055 g), design-basis (0.15 g), and rare (0.31 g) earthquake levels, respectively, and direct-integration nonlinear time-history analyses are performed. Compared with the frame without dampers, the BRB model M2 and the FVD model M3 reduce the maximum inter-story drift ratio at all three levels. The reductions under frequent earthquakes are 36.7–42.7% and 41.9–54.6%, respectively; under design-basis earthquakes, 12.3–45.8% and 18.8–20.0%, respectively; and under rare earthquakes, 21.4–39.9% and 11.2–26.2%, respectively. Among the analyzed cases, M3 is more favorable for floor-displacement control under frequent and design-basis earthquakes, while M2 performs better in controlling the maximum inter-story drift ratio under rare earthquakes. The average additional damping ratios of the two models under the three earthquake levels are 1.33%, 1.98%, and 3.10% and 3.90%, 3.28%, and 2.30%, respectively. On this basis, two BRB and two FVD candidate layouts are established, each with 48 devices. Four sets of near-fault ground motion records with identified pulse azimuths are selected, and the horizontal components in the pulse azimuth and its orthogonal direction (W7–W14) are used for analysis. Under rare earthquakes, the inter-story drift ratio-oriented B–D scheme reduces the mean maximum inter-story drift ratio by 2.83% compared with the story shear-oriented B–S scheme; the inter-story relative velocity-oriented F–V scheme reduces it by 3.77% compared with the floor absolute acceleration-oriented F–A scheme. The differences in the mean peak roof absolute acceleration between the two groups of candidate schemes are both less than 0.5%. The results provide a reference for selecting candidate layouts by combining control objectives and device working characteristics.