Abstract
This study presents a tube-in-tube buckling-restrained brace (BRB) infilled with lightweight and rapid hardening polymer. The proposed BRB consists of a circular or square tube core encased with a tube of similar shape and polymer infill. The tube-in-tube arrangement minimizes the filler material volume and enables the use of rolled steel section as opposed to welded profiles commonly utilized when large BRB axial strength is required, although welded profiles suffer from low assembly accuracy resulting from welding deformation. The infilled polymer has a density of approximately half that of mortar and requires a curing time of 24 h, enabling weight and fabrication time reduction. The stability and inelastic deformation capability of the BRB were investigated through brace and subassembly tests of six circular and four-square full-scale specimens, followed by finite element analysis. The test results show that circular BRB designed with a Pcr/Py ratio of 1.46 exhibited a stable hysteresis up to 1.42% and 1.06% core strain in tension and compression, respectively. Circular and square specimens designed with Pcr/Py ratios ranging from 0.82 to 1.06 exhibited stable hysteresis before failing by global buckling at compressive core stains ranging from 0.86% to 1.09%. The slot weld detail adopted for welding core projection stiffener displayed a stable performance in circular BRB specimens, while it resulted in large plastic strain demand in square BRB specimens, leading to core fracture at tensile core strains ranging from 0.64% to 0.71%.
Highlights
Buckling-restrained braces (BRBs) have been widely utilized to enhance the seismic performance of new and existing buildings as well as for post-earthquake retrofitting [1,2,3,4,5,6].buckling-restrained brace (BRB) differ from conventional braces because the BRB core yields under both tension and compression without buckling
This paper proposes polymer infilled tube-in-tube BRBs to eliminate the drawbacks of concrete/mortar-filled BRBs
Circular specimens designed with Pcr /Py, and Pcy /Py ratios of 1.46 and 1.2 exhibited a stable hysteresis response up to 1.42% and
Summary
Buckling-restrained braces (BRBs) have been widely utilized to enhance the seismic performance of new and existing buildings as well as for post-earthquake retrofitting [1,2,3,4,5,6]. BRBs differ from conventional braces because the BRB core yields under both tension and compression without buckling. The core sustains axial tension and compression without buckling under the restraining effect of the casing and filler material. The long curing time and high density of concrete/mortar negatively affect the fabrication time and dead-weight of such BRBs. The long curing time and high density of concrete/mortar negatively affect the fabrication time and dead-weight of such BRBs To address these drawbacks, and in a few cases to allow disassembly and inspection, several all-steel BRBs, including flat, cruciform, and H-section core BRBs, have been proposed and tested [12,13,14,15]. When large BRB axial strength is required, cruciform, H-section, or other core profiles are better alternatives to a thick flat plate core. Nonlinear finite element analysis [21,22,23] was conducted to better understand the proposed BRB
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