Seismic Design of Diaphragms in Steel Buildings
A Warren Distinguished Lecture and
Robert Dexter Memorial Lecture with
Matthew Eatherton
Civil and Environmental Engineering, Virginia Tech
ABSTRACT
The critical role of a diaphragm in the lateral force resisting system was demonstrated during the 1994 Northridge Earthquake when several parking garages collapsed due to diaphragm deficiencies. Subsequent research found that equations in the US building codes severely underestimate the magnitude of lateral force that can occur in diaphragms during design earthquakes. Significant development has occurred in the past two decades on a new approach to diaphragm design that considers inelasticity in both vertical elements (e.g., braced frames, moment frames) and horizontal elements (i.e., diaphragm). This development represents a significant shift in how researchers and engineers think about diaphragms, leading to a substantial amount of critical new information necessary to support ductile diaphragm design procedures. The Steel Diaphragm Innovation Initiative (SDII) was a multi-university research project conducted to develop a better understanding of diaphragms in steel buildings and improve design procedures. The SDII project included 1) several experimental studies ranging from component-level tests up to full-scale diaphragm tests, 2) several computational studies ranging from simple mass-spring models up to nonlinear response history analyses of archetype 3D building models, and 3) an evaluation of code provisions, which has led to many code changes in the U.S. Eatherton provides an overview of the SDII project, an introduction to seismic diaphragm design considering inelasticity, and some discussion of implications for the design of steel deck diaphragms.
SPEAKER
Matthew Eatherton is the Montague-Betts Professor of Structural Steel Design in the Department of Civil and Environmental Engineering at Virginia Tech. He conducts research on diaphragms and floor systems in steel buildings, as well as seismic design of steel structures. He is a part of the Steel Diaphragm Innovation Initiative (SDII, www.steeli.org) that won an AISC Special Achievement Award in 2024 for their contributions to diaphragm design in steel buildings. He has seven years of practicing structural engineer experience and eighteen years of academic experience. He has been awarded several honors including the AISC Milek Faculty Fellowship, NSF Career award, AISC Early Faculty Award, ASCE Moissef Paper Award, and the Curry Faculty Fellowship at Virginia Tech.