The lateral-torsional buckling capacity of steel girders can be improved with the addition of intermediate bracing. One form of bracing commonly used in the building industry is profiled sheeting that acts as a shear diaphragm to restrain the warping deformation of the top flange. Although metal deck forms are also commonly used in the bridge industry, the forms are not currently permitted to be relied upon for bracing due to flexibility in the connection method. Shear diaphragms attached to the top flange of adjacent girders can be relied on for bracing provided they have adequate stiffness and strength, both of which are sensitive to the connection details. Shear diaphragms may be engaged to act as lateral bracing by connecting the diaphragm along either two or four sides. A common connection detail consists of connecting the diaphragm along two edges that are parallel to the longitudinal axis of the girder and studies have been carried out to develop strength requirements for suitable bracing. Provisions have not been adequately developed in stiffened diaphragms when the stiffening members are perpendicular to the longitudinal axis of the girder. This paper documents a computational study to develop strength requirements for stiffened diaphragms used for stability bracing.
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