Concrete-filled cold-formed chord studs to improve the seismic performance of steel framing buildings

Abstract

Light gauge steel framing is increasingly used, mainly for low-rise buildings. However, for mid-rise buildings, their lateral strength is rather low; therefore, seismic effects can be highly demanding. Steel bracing has been proposed for such buildings, but the chord studs are severely overloaded, thus limiting the building seismic performance (European codes state that, for a ductile behavior, the chord studs need to withstand the maximum force that can be transmitted by the braces). In some cases, steel-only solutions might be insufficient; this paper investigates the use of concretefilled cold-formed built-up sections for the chord studs. Three 5, 7 and 10-story prototype buildings located in seismic areas (PGA 0.2, 0.3 and 0.4 g) are analyzed. A previous study showed that steel-only solutions are only feasible in some cases: 5 and 7-story buildings for PGA 0.2 and 0.3 g, and 10-story building for only 0.2 g. On the contrary, by using concrete-filled built-up sections in the chord studs of the bottom and mid-height levels, in all the cases all the design requirements have been satisfactorily fulfilled.