A Comparative Study of AISC341 and EC8 Provisions for Design of Steel Concentrically Braced Frames

Steel concentrically braced frames (CBFs) are used as an efficientlateral load resisting system to resist earthquakes and wind loads. Thebrace members in CBFs dissipate energy by buckling undercompression and yielding under tension. Behavior of CBFs during anearthquake is complex because of the instability and yielding history ofthe braces. Widely used seismic specifications such as the AISC341and EC8 have somewhat different philosophies and approaches fordesign of CBFs in seismic areas. Our study evaluated in detail thesimilarities and differences between the design provisions used in theUnited States (AISC341-10) and Europe (EC8-1998) for thesesystems. The comparative studies and associated case studies indicatedthat the primary difference between the specifications arise from thedesign of brace members. The US seismic design provisions are basedon the pre-buckled stage of the members where buckling strength of thebracing member in compression and yield strength of bracing intension are considered in design. On the other hand the Europeandesign provisions are based on the post-buckled stage of the memberswhere the braces in compression are ignored and only strength ofbraces in tension are considered in design. These different approachesresult in different structural models to be considered during the designstage. The differences were studied using a 10 story CBF designedaccording to both ASCE241 and EC8 seismic specifications. In thispaper, the details of the comparative study are presented along withobservations that are useful for practicing engineers.

کلیدواژه ها:

Concentrically braced frame ، seismic ، design provisions