This technology is a buckling-restrained brace featuring a rectangular core member placed inside a hollow, elongated external casing. An unbonded band, narrower than the width of the long side, is attached only to the center of both long sides of the core member, and the remaining space is filled with filler material.
Braces that resist seismic loads are prone to lateral or local buckling under high compressive forces, which reduces their strength before yielding; thus, buckling-restrained braces were developed to prevent this. However, in conventional buckling-restrained braces, high-order mode buckling in the in-plane and out-of-plane directions occurs in the space occupied by the debonding material between the mortar and the core, causing the external casing to bulge locally. To prevent this, the non-load-bearing casing is often made thicker, leading to uneconomical steel consumption.
This technology prevents the external casing from being pushed outward when the core member undergoes out-of-plane deformation due to compression, as the unbonded band at the center of the long side interrupts stress transfer between the filler and the core. By adding a closed-section steel tube or U-shaped steel plate covers at both ends with vertical bent supports, the filler can be protected from bearing stress bypassing the band. Thinner unbonded covers and casings with arc-shaped sides can also be used. Applicable to 20–50 story braced frame high-rises, schools and hospitals requiring seismic retrofitting, and steel factories or warehouses, this design suppresses local out-of-plane deformation without increasing casing thickness, reducing steel usage per brace while ensuring stable energy dissipation until yielding.
This invention was developed with support from the Ministry of Land, Infrastructure and Transport's project for the development of integrated risk management package technology for facility safety.
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