Seismic Design of Steel Framed Structures with High-Ductility Knee Braces

Steel structures possess high strength and significant ductility, thus areeffective structural forms for earthquake-resistant designs. Structuraldesigns using special moment resisting frames (SMRF) are usuallyconsidered when high ductility is required. In order to improve the seismicperformance of the structures, a modified structure adopting knee braces,namely knee-braced moment resisting frame (KBRF), is proposed. It hasbeen validated that the application of knee braces to steel frameseffectively alleviated the stress in the beam-to-column joint regions. It isalso proven that the structural performance can be effectively sustainedshould the knee brace integrity be maintained.This study is focused on the performance evaluation and developmentof KBRF structures equipped with high-ductility knee braces. Thehigh-ductility knee braces are composed of trimmed low yield strengthsteel plates with desired dimensions and stiffened confined plates. A seriesof cyclic loading tests will be conducted on the SMRF and KBRFstructures with soft stories. Test results will be used to, based on theperformance based design principles, evaluate the structural performanceand to establish the seismic designs of KBRF structures.