Steel Diaphragm Innovation Initiative Improves Seismic Design Tools

In a few months, Northeastern University expects to make research history by testing the behavior, under seismic loads, of a full-scale, composite, concrete-filled steel-deck diaphragm system. The novel experiment culminates unprecedented collaborative research on the seismic performance of steel floor and roof diaphragms in steel structures. The five-year initiative already has aligned and improved design methods and relevant standards used throughout the U.S., not merely in high-seismic zones, according to those involved. Get more news about steel structure building,you can vist our website!

The program not only validates current design practices for different steel structures, it also promises to improve the seismic design and behavior of “bare” and concrete-topped decks under earthquake loads, says Ben Schafer, a professor of civil engineering at Johns Hopkins University and principal investigator for the nearly $2-million Steel Diaphragm Innovation Initiative. The design tools developed allow “more reliable designs” for seismic performance and offer slight efficiency gains that can result in the application of less concrete as a deck topping, Schafer says.
The findings also pave the way for future explorations that could speed design and onsite construction. These include the study of modular deck systems and bare metal floor decks that are free of concrete topping, says Schafer.

Known as corrugated metal decking, steel diaphragms are ubiquitous in steel frames. They are considered advantageous because they are relatively low weight, use recycled material and offer potential redundancies from a large number of connection points between the diaphragm and other structural elements, say the sponsors of the initiative, which include the American Iron Steel Institute (AISI), the American Institute of Steel Construction (AISC), the Metal Building Manufacturers Association, the Steel Deck Institute, the Steel Joist Institute, the Cold-Formed Steel Research Consortium and structural consultant Walter P Moore.

The investigation has resulted in the adoption of new provisions in seismic codes and standards that will increase the already high level of seismic safety of steel buildings, according to AISI, which, along with the other sponsors, is trying to make steel structures more attractive to engineers. These efforts expanded the capabilities of structural engineers to successfully employ steel in seismic diaphragm systems in essentially any situation,” say the authors in a 101-page final report on the research, published in March by AISI and released last month.

Until the recent research, funded by $1.4 million from the sponsors and $540,000 from the National Science Foundation, data had not been compiled and research was largely focused on the strength of isolated systems instead of ductility or whole-building performance, according to participants.

The initiative involved myriad design simulations and physical testing. The work resulted in a better understanding of diaphragm-structure interaction. That in turn led to new design approaches and new 3D modeling tools, say the researchers.