Inelastic Analysis of Bare Steel Deck Diaphragms Using the Instantaneous Center Method

Steel deck diaphragms are currently analyzed using elastic analysis, where the assumed strength limit is reached when the first fastener reaches its elastic strength limit. The objective of this study is to determine whether an alternative inelastic analysis method of bare steel deck diaphragms using the instantaneous center method (ICM) offers a feasible design approach, expanding its application from the use in bolted and welded connections. To implement the ICM, this study considered diaphragms that incorporate various types of fasteners such as arc spot welds and screws. Inelastic load–deformation relationships of these fasteners, required by the ICM, were obtained from the literature. Diaphragm strengths estimated using the ICM were then compared with diaphragm experimental results from published sources. In addition, this study developed computational notebooks for implementing the ICM for diaphragms. These computational notebooks, accompanied by annotated Python code and user-friendly execution instructions, are accessible via an open source repository. Users can readily utilize these notebooks online without the need for local software downloads, making this analysis method easily accessible to future practitioners. Although further refinement of the proposed approach is necessary, this paper presents the framework that can be further developed.