American Iron and Steel Institute (AISI) Specifications, Standards, Manuals and Research Reports (1946 - present)

Alternative Title

Research Report RP21-04



The Steel Diaphragm Innovation Initiative (SDII) is a multi-year industry-academic-government partnership to advance the seismic performance of steel floor and roof diaphragms utilized in steel buildings. This report provides a final report for Year 5 of the overall 5-year SDII plan. Contributions in the final 12 months (1 Jan. 2020 – 31 Dec. 2020) include the following highlights.

Innovation and Practice:

  • Adoption in ASCE 7 of new provisions for bare steel deck including methods for buildings with rigid walls and flexible diaphragms, alternative diaphragm design with Rs, and special seismic detailing (following on from successful adoption in NEHRP and AISI S400).
  • Adoption in ASCE7 of new provisions for concrete-filled steel deck alternative diaphragm design (Rs) procedures (following on from successful adoption in NEHRP).
  • Adoption in AISI S310 of new provisions for strength of concrete-filled steel deck.
  • Finalization in AISC 342 of new procedures for bare and concrete-filled steel deck diaphragms that recognize inelasticity and AISI S310 for strength.
  • Adoption in AISC 360 (approved in current AISC ballot, closeout of AISC 360 balloting has not yet happened) of the use of AISI S310 for strength of concrete-filled steel deck.
  • Evolution of fuse and leaf-spring concepts for dedicated and controlled energy dissipation in large concrete-filled steel deck diaphragms in preparation for proof-of-concept testing.


  • Completed concrete-filled steel deck cyclic cantilever diaphragm tests. These tests provide experimental support for concrete-filled steel deck strength provisions being developed for the next code cycle in AISI S310 and ductility/seismic detailing provisions for the next code cycle of AISC 341 and 342.
  • Completed design, detailing, and acquiring steel for full building bay diaphragm tests which will complete in 2021 and be provided as an addendum to this report.


  • Completed a report summarizing the seismic performance of 1-12 story steel-framed buildings with buckling restrained braced frames demonstrating that the use of diaphragms designed with the alternative method and Rs = 2.0 for concrete-filled steel deck and Rs = 2.5 for bare steel deck is appropriate for this building system.
  • Completed a parallel modeling effort on concentric braced frames, demonstrating that the alternative diaphragm design method with appropriate Rs provides improved prediction of diaphragm design forces in these building systems leading to acceptable collapse probabilities when compared with traditional design.
  • Completed extensive single story and multiple story mass-spring model studies that definitively explore interaction between yielding in walls and diaphragms and evaluates methods currently available to designers for force prediction and ductility demands.
  • Completed optimization effort that provides optimized steel deck layouts, even for plan-irregular buildings, with marked performance improvements over conventional design.


Civil, Architectural and Environmental Engineering


American Iron and Steel Institute (AISI)

Publication Date

March 2021

Document Version

Final Version


© 2021 American Iron and Steel Institute, All rights reserved.


Year 5 Final Report: (1 Jan 2020 - 31 Dec 2020)

An addendum to this report is available here or from the Full Text Link in the sidebar above.

Document Type

Technical Report

File Type




Technical Report Number