Shear Diaphragm Bracing of Beams. I: Stiffness and Strength Behavior

Abstract

Light gauge metal decking is commonly used in the building and bridge industries for concrete formwork. In addition to supporting the concrete, the metal forms also improve the lateral-torsional buckling capacity of the beam or girder they are fastened to as they behave as a shear diaphragm and restrain the warping deformation of the top flange. However, the stability bracing requirements for shear diaphragms are not well established. This is the first part of a two-part paper on diaphragm bracing of beams. The first part of the paper focuses on behavior whereas the second part focuses on general design requirements. The diaphragms in the study were connected along two edges to the top flanges of adjacent girders. The parameters that were investigated include the diaphragm stiffness, load type, and load position. The type of loading has a significant effect on the stability bracing behavior of the shear diaphragm. Other factors that have an effect on the bracing behavior include the web slenderness and the presence of intermediate discrete braces. The results presented in the first part of the paper create the foundation for a diaphragm bracing design methodology that is developed and presented in the second part of the paper.