In-plane shear stiffness of bare steel deck through shell finite element models
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The objective of this report is to explore the in-plane elastic shear stiffness of bare steel deck diaphragms through high fidelity shell finite element modeling. Profiled steel panels, i.e, metal deck, often serve as a key distribution element in building lateral force resisting systems. Acting largely as an in-plane shear diaphragm, metal deck as employed in walls, roofs, and floors plays a key role in creating and driving three-dimensional building response. Accurate prediction of shear stiffness is needed to better understand the shear behavior of bare steel deck. According to the shear stiffness expression in AISI S310 or SDI’s Diaphragm Design Manual (DDM), total shear deformation can be separated into three parts: pure shear deformation, warping deformation, and connection slip. In this report, bare deck finite element models were built with typical fastener layouts from DDM. The shear condition was performed on the models by imposing deformations at the perimeter. By changing boundary conditions, these shear deformation terms can be separated and the values of shear stiffness were compared with DDM expressions. The results showed that the prediction of shear stiffness from pure shear deformation and connection slip from finite element modeling agree well with the DDM prediction; however, the warping stiffness predicted from DDM is smaller than shell finite element predictions. DDM uses a simplified model to predict warping deformation and this model may need to be revised in the future.