ABSTRACT
Lightweight BRBs constructed of all-steel components have been proposed but have not been able to achieve weight savings greater than 40% over mortar-filled steel tubes. All-steel varieties comprised of prismatic/hourglass or stiffened/ unstiffened flat bar and H-shaped (Ju et al., 2009) cores surrounded by steel tubes, channels, omega-sections and plates either bolted or welded together have been proposed. Benefits of all-steel BRBs have been explained as lightweight (Usami et al., 2009), less expensive and easier to construct (Tremblay et al., 2006), having replaceable cores (Chou & Chen 2009), detachable (Mazzolani et al., 2009) or compact for installation in existing building walls (D’Aniello et al., 2008, 2009). These configurations often led to either global flexural buckling about the weak axis, high frictional forces caused by Poisson expansion or steel guide plate
1 INTRODUCTION
1.1 Combination of three technologies
The ultra-lightweight buckling-restrained brace (ULWBRB) combines three technologies that are individually at the forefront of incorporation into civil engineering structures. These are BRBs, structural aluminum seismic dissipaters and fiber reinforced polymers (FRP). The ULWBRB brings these materials together to create a seismic brace member that can be installed in buildings with minimal required equipment. Similar to traditional BRBs, the ULWBRB has the capability of dissipating seismic energy through fully-reversed, symmetrical cyclic plastic straining of a ductile aluminum core thus protecting portions of the structure designed to remain elastic. Buckling preclusion is accomplished by surrounding the core with a flexurally stiffer FRP jacket that allows the core to slide independently within. During cycling, the FRP jacket remains elastic and is not intended to carry axial load.
