Analytical Study on the Stability of Collector Members in Composite Steel Structures

Abstract

Seismic collectors transfer seismic forces to the primary vertical elements of the Seismic Force Resisting System (SFRS). In steel structures, collectors are typically elements in the floor framing system specially designed to carry these forces primarily though axial thrust. Steel collector members are designed as beam-columns under the compressive collector action. The controlling limit state in design may be strong axis beam-column behavior, weak axis buckling, torsional buckling or constrained-axis flange torsional buckling depending on the bracing condition providing by the floor slab or roof deck system attached to the collector. This paper presents an analytical study examining the stability behavior of steel seismic collectors under different structural configurations, including roof deck and composite slab. The orientation of the deck and slab is alternated between the parallel and deck perpendicular configurations, relative to the collector. The sizing of collector members, collector connections, and gravity system members are based on the design of a prototype structure in order to evaluate collectors under realistic design conditions. The compression strength of collector elements under these conditions is compared to design values per the American Institute of Steel Construction (AISC). Design considerations are provided for the stability design of steel seismic collectors.