Development of cross-anchored dual-core self-centering braces for seismic resistance

Abstract

The steel dual-core self-centering brace (SCB) is an innovative structural member that provides both energy dissipation and re-centering properties to structures, reducing the residual drift of braced structures in earthquakes. The axial deformation capacity of the brace is doubled by using two inner cores and one outer box and by serial axial deformations of two sets of parallel tensioning elements. The original dual-core SCB that used E-glass fiber tendons or T-700 carbon fiber tendons as tensioning elements exhibited good self-centering and energy dissipation up to an interstory drift of 2.5%. The new cross-anchored dual-core SCB halves the work required to apply the initial post-tensioning forces to tendons. The potential use of high-strength steel tendons as tensioning elements is studied herein, and the effects of the number of cycles on the brace behavior, energy dissipation, and durability of the steel tendon-anchorage system are also examined. First, the mechanics and cyclic behavior of the new brace are explained; a 7950mm-long cross-anchored dual-core SCB is then tested six times. The cross-anchored dual-core SCB exhibits excellent self-centering property up to a drift of 2.5% and a maximum axial load of 1700kN. No damage to the steel tendons, anchors or bracing members is found after three cyclic loading tests with increasing displacement amplitudes and 60 low-cycle fatigue tests. Finite element analysis further confirms the hysteretic responses and mechanics of the cross-anchored dual-core SCB in the cyclic test.