Shear Diaphragm Bracing of Beams. II: Design Requirements

Abstract

Light gauge metal decking is commonly used in the building and bridge industries for concrete formwork. In addition to supporting the wet concrete, the metal forms also improve the lateral-torsional buckling capacity of the beams or girders they are fastened to since they behave as a shear diaphragm and restrain the warping deformation of the top flange. The design requirements for shear diaphragm bracing are not well established. This is the second part of a two-part paper. The first part of the paper focused on the general stability bracing behavior for shear diaphragms connected to the top flanges of adjacent beams or girders. This part of the paper outlines the design requirements for shear diaphragm bracing and focuses on both the stiffness and strength requirements for beam stability. Design expressions are presented for the stiffness and strength requirements as well as a model that can be used to estimate the forces in the fasteners that connect the diaphragms to the top flanges of the beams. An example is presented at the end of the paper demonstrating the use of the design expressions.