Investigation of Seismic Performance of Double-Angle Braces with Single Lacing under Two-Step Variable-Amplitude Cyclic Loading

Aceh Province, which is located in an earthquake-prone area, requires an earthquake-resistant structure, i.e., a Concentrically Braced Frame System (CBFs). The CBFs have brace elements installed diagonally on the structure, and it reduces horizontal displacement in the structure due to the earthquake. This study implemented several Two-Step Variable Amplitude (TSVA) loading histories, consisting of two cyclic uniform load blocks with low and high amplitudes, which represent a simplification of earthquake loads due to amplitude changes. The test was conducted by installing the CBF brace in the loading frame and applying the TSVA parallelly with long axis of the brace. The experimental study yielded that the CBF brace with the largest cyclic ranges exhibited the highest strength, stiffness, and dissipated energy. Furthermore, the braces tested under TSVA with less uniform repeated cycles exhibited better strength, stiffness, and dissipated energy, which corresponds to the smaller fatigue effect in the CBF brace, thereby enhancing their seismic capability. Observing the failure modes of the CBF brace indicated that all the specimens experienced flexural buckling due to the TSVA loading histories.