Stiffness and Strength Requirements of Shear Diaphragms Used for Stability Bracing of Steel I-Sectio

O. Ozgur Egilmez Izmir University of Economics Izmir, Turkey

Mustafa Vardaroglu and Andac Akbaba Izmir Institute of Technology Izmir, Turkey

Lateral torsional buckling is a failure mode that often controls the design of steel I-beams during construction. During this critical stage, the buckling capacity of the beams can be increased by reducing the laterally unbraced length by providing bracing at either discrete locations or continuously along the length of the beam. Light gage metal decking, which is often used in the building and bridge constructions as concrete deck formwork, acts like a shear diaphragm and can provide continuous lateral bracing to the top flange of non-composite beams and girders by restraining the warping deformations along the beam/girder span. Past studies that investigated the stiffness and strength behavior of shear diaphragms used to brace steel beams mainly focused on the strength of the end connections (sheet to beam connections along the length of the beam). However, the strength of a diaphragm is generally controlled by either the shear strength of the end connections or shear strength at interior connections between panels. Therefore, strength requirements for shear diaphragm bracing should ad-dress both end and sidelap fasteners. This study investigates the stiffness and strength behavior of shear diaphr

agms used to brace stocky and slender beams/girders by taking into account both end and sidelap fastener connections. A simple finite element analytical model is utilized in the study that enables the end and sidelap fasteners to be separately modeled. The parameters that are investigated include diaphragm stiffness, thickness, and width, number of side-lap fasteners, web slenderness ratio, and section depth. The results indicate that web slenderness ratio is not as much effective as section depth on fastener forces. The findings of the study will be used to develop strength and stiffness requirements for shear diaphragms used to brace steel beams.

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