Development of Steel Deck Diaphragm Seismic Design Provisions for ASCE 41/AISC 342
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The objective of this report is to provide the background work for the development of recommended seismic design provisions for steel deck diaphragms utilizing ASCE 41 / AISC 342. The current (2017) edition of ASCE 41 for the seismic evaluation and retrofit of existing buildings essentially requires that steel deck diaphragms be designed as elastic elements. This potentially results in large economic and design inefficiencies. Recently existing data has been gathered on the cyclic performance of steel deck diaphragms and this data indicates that appreciable ductility can exist in these systems. Following protocols established in ASCE 41 this document uses existing data to develop acceptance criteria and modeling protocols for seismic performance-based design supported by linear or nonlinear analysis. The method requires fitting a multi-linear model to the cyclic backbone response of available data – and parametrically characterizing the fit to the extent possible. It is found that with minor changes the provisions of AISI S310 may be used to establish strength and stiffness and the available test data to determine ductility and post-peak response. Differences between ductility of diaphragms in buildings and diaphragms in sub-assembly tests are noted and recommendations made to handle this difference. Specific new provisions, ready for adoption by AISC 342 / ASCE 41 are recommended for bare steel deck diaphragms and steel deck diaphragms with concrete fill. A list of future challenges, including the need for additional cyclic testing on steel deck diaphragms with concrete fill, are provided.