The Steel Diaphragm Innovation Initiative (SDII) is a multi-year industry-academic partnership to advance the seismic performance of steel floor and roof diaphragms utilized in steel buildings through better understanding of diaphragm-structure interaction, new design approaches, and new three-dimensional modeling tools that provided enhanced capabilities to designers utilizing steel diaphragms in their building systems. The formal research phase of SDII was conducted from 2015-2020, but activities continue as research is finalized and technology transfer to engineers ramps up.
SDII was created through collaboration between the American Iron and Steel Institute and the American Institute of Steel Construction with contributions from the Steel Deck Institute, the Metal Building Manufacturers Association, and the Steel Joist Institute in partnership with the Cold-Formed Steel Research Consortium; including, researchers from Johns Hopkins University, Virginia Tech, Northeastern University, and Walter P Moore. SDII also worked with additional internal industry partners and external (federal research, state research, foundation) partners to advance its objectives.
Steel deck diaphragms have a number of strengths: low weight, use of recycled material, competitive cost, and a large number of connection points between the diaphragm and other structural elements creating potential redundancies. In addition, steel diaphragm systems may be realized across a wide range of stiffness (from bare steel deck to concrete-filled floor and roof systems) giving the designer a great deal of flexibility. However, at the outset of SDII’s research phase weaknesses were identified as well: limited data on performance, and available data focuses on strength of isolated systems, not the ductility nor the whole building performance. Steel diaphragm design lacks a design paradigm consistent with seismic performance-based design. Further, insufficient knowledge and expertise existed at the outset of the SDII effort to refute or improve upon design proposals advanced by other industries that have the potential to negatively impact steel diaphragms.
The opportunity to consider steel diaphragms as a system, an integral part of the building, and not just as a distribution element is significant. As we re-engineer steel diaphragms for seismic performance the potential to fully consider new demands such as energy, acoustic, fire, all provide a means to advance performance in novel ways. In addition, advancing our understanding and modeling of diaphragms is the most important piece in the puzzle towards modeling, designing, and optimizing buildings as fully three-dimensional – significant opportunities open up for the first to harness this approach. At the outset of SDII it was recognized that without innovation in steel diaphragms threats exist: multi-year research investment in other materials, particularly in seismic performance, has created a knowledge gap that is now being realized in design specifications that are unfavorable to steel diaphragms. Since the floor system can drive the material choice in the building system, lack of innovation in steel diaphragms may impede adoption of other steel solutions. Further, without innovation, steel diaphragms will be threatened by advances made by competing diaphragm solutions. SDII utilized the strength of steel solutions and capitalized on the opportunity to overcome the weakness and threats the industry faced to develop a series of solutions which are described in detail on this website.