Full Session without Abstracts
Significant research is underway to improve our understanding of the behavior of floor diaphragms, chords, and collectors in steel buildings under seismic demands and translate these findings to improved code provisions. This work is, in part, a response to the new alternative diaphragm design provisions developed and adopted in ACE7-16. This session will report out on the latest findings from the Steel Diaphragm Innovation Initiative (steeli.org) and two National Science Foundation funded research efforts to address these issues. A series of new three-dimensional steel building archetypes have been designed to provide a central focus to the effort. New experiments are being conducted on steel deck-concrete composite diaphragms, related chord and collector details, and smaller-scale connector tests. The existing database of steel deck-concrete composite diaphragms is limited and further testing is needed to properly understand the performance. Despite the critical nature of seismic collectors, no research effort, including physical testing, has focused specifically on collectors, and knowledge of their seismic performance is lacking. A challenge in understanding the performance of seismic collectors is the complex nature of the floor system itself, a complicated assemblage of many components of different materials at different elevations, with multiple purposes and uncertain force paths. The experiments are being supplemented by detailed high fidelity modeling to better understand the internal flow of forces in these complex systems even when steel fracture or concrete cracking is involved in the post-peak response. In addition, reduced order models are being used to elucidate the resulting building system behavior as a function of the diaphragm, chord, and collector design choices. The reduced order models also provide a means to study the impact of different diaphragm and collector design provisions (past, existing, and proposed) on building performance. The session presenters include the principal researchers in these efforts.