Warping and Deformations in Profiled Steel Deck under Shear

The objective of this paper is to evaluate currently available methods for predicting the warping and other deformations that occur in bare steel deck profiles under shear. Profiled steel panels often serve as the diaphragm in single-story buildings and thus are the main element for distributing lateral forces to the walls. As a diaphragm they largely undergo in-plane shear. Thus, the in-plane shear stiffness of these panels is of crucial importance in design. The American Iron and Steel Institute (AISI) S310 Specification and Steel Deck Institute's Diaphragm Design Manual (DDM) provide an analytical approximation for determining the shear stiffness based on contributions from the deck in pure shear, connection slip, and warping of the deck. Due to the thin-walled nature of the deck geometric nonlinear deformations can be important and stability of the deck profile can also influence the stiffness results. The prediction of the warping deformations is based on a simplified two-dimensional beam on elastic foundation approximation that is explained in detail herein. This model is an approximation of the actual three-dimensional deformations. Shell finite element models are constructed in ABAQUS to examine the deck shear displacements and idealized boundary conditions are introduced to isolate the deck deformations and compare with the approximations in DDM/AISI S310. Comparison of the results indicates that improvements in the DDM/AISI S310 model for predicting warping are possible; as is generalization of the approximate method employed. Shell finite element predictions of pure shear stiffness and connection slip are found to be in good agreement with DDM/AISI S310. This work is part of the larger Steel Diaphragm Innovation Initiative and aims to understand and optimize the behavior of steel deck diaphragms.

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