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.

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.

这些发现还为未来的探索铺平了道路，可以加快设计和现场构建。Schafer说，其中包括研究模块化新利18备用甲板系统和无混凝土浇头的裸露金属地板甲板。

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.

调查导致的采用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.

“这些努力扩大了结构工程师在地震隔膜系统中成功使用钢的能力，这实际上是任何情况。”作者在3月由AISI于3月发布的101页最终报告中说，并于上个月发布。

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.

Under the study, researchers considered steel diaphragms as a system that is an integral part of a building.

“The ductility in these systems can be quite good and helps to address any variability in forces that might occur due to the variability in earthquakes,” says Jerome Hajjar, a professor of civil engineering at Northeastern University and a co-principal investigator, with professors of civil engineering Matt Eatherton, at Virginia Polytechnic Institute and State University; and Sam Easterling, at Iowa State University. In total, there were 21 investigators involved in the research.

Unified Design Requirements

“The project unified design requirements, creating a cohesive basis” across the National Earthquake Hazards Reduction Program Provisions and relevant standards from the American Society of Civil Engineers, AISC and AISI, says Charlie Carter, AISC’s president. The unified requirements also will render the next edition of the model International Building Code “similarly cohesive,” he adds.

Achieving corresponding changes in the standards required “extensive coordination” among the standards-writing committees, says John D. Hooper, director of earthquake engineering at Magnusson Klemencic Associates and an ASCE 7-22 committee member.

具体而言，AISC 342，ASCE 7-22和AISI S400的钢板和屋顶膜片的设计方法发生了变化。这些更改包括建立特殊的地震细节需求，以确保钢甲板膜片的延展性和变形能力，并建立使用特殊的Seistic细节和含混凝土填充的钢甲板的裸钢板diaphragms，以裸露的deck deaphragms建立diaphragm Desimage降低功率。

“For the first time, engineers are able to reliably provide ductility and deformation capacity in steel-deck diaphragms,” says Hooper. This will be especially helpful in the design of rigid-wall, flexible-diaphragm structures where the ductility comes from the roof diaphragm, he adds.

For this, researchers expanded building archetype designs. They performed thousands of nonlinear time-history analyses of 3D steel buildings and validated the alternative-diaphragm design procedures for concrete-filled steel decks and for bare steel decks in buckling restrained braced frames and concentric braced frames.

The program kicked off in 2015. The final report is available for free download on the AISI website, under “reports.”

To date, research has been conducted in the form of cantilever diaphragm tests, generally designed to identify the effect that one factor has on strength and behavior of the system. The Northeastern test system builds off the knowledge gained from these previous tests but advances beyond typical assumptions and necessary simplifications of cantilever diaphragm tests, says Hajjar.

东北，多湾测试程序旨在记录典型复合隔膜的固有强度和延展性，并为未来探索创新的膜片设计提供了基线测试。28英尺乘20英尺的标本包括两个跨越28英尺的和弦成员，两个跨度为20英尺的收集器成员将附加到最终报告中。

填补知识空白,focu五年计划sed on traditional floor systems. Time was limited for study of irregular situations, such as floor cutouts, irregular floor plans and eccentric architecture, which create unusual demands on the diaphragms.

Schafer hopes to study special cases in the future, along with bare decks and modular systems. For now, the focus is on educating practitioners about changes in the codes and standards so they can take advantage of the advances.