Design and behaviour of eccentrically braced frames in moderate seismic zones

EBF seismic design conforming to Clause 27 of CSA-S16.1-94 is described and a computer program to carry out the ductility design (EBFSD) was developed for this study. EBF design procedures for different seismic load levels are proposed. Twenty-two EBFs incorporating different link lengths, numbers of storey, and wind-to-earthquake load ratios are designed and analyzed for a moderate seismic zone. The loads controlling member selection in a frame are identified from various load combinations considered in the design phases. The extent of seismic overstrength design for an EBF in a moderate seismic zone is investigated. Enhanced strength of ductile links due to non-seismic loads may cause the ductility demands on the links to be reduced.The strengths. stiffness. and ductility of the frames with the resulting members from the proposed design procedures are investigated. A simple method of evaluating overall frame strength and ductility is outlined. Detailing of the links for moderate seismic loads is proposed based on the analytical results. The results indicate that EBF design with the proposed procedures is feasible and practical