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This volume provides: a) an overview of bracing utilized for I-girders, b) a discussion of the bracing systems for tub girders, and c) design requirements for the members and connections of bracing systems.
Torsional brace strength requirements for steel I-girders. Yangqing Liu1, Matthew C. Reichenbach2, Todd A. Helwig3. Abstract. Torsional bracing is often used to stabilize beams in building and bridge applications. The bracing improves the stability by restraining twist of the cross section.
Torsional bracing is aimed to prevent twisting of the cross-section and improve lateral-torsional buckling (LTB) strength of steel I-girders (Fig. 1). Bridge girders with torsional bracing are usually designed assuming that buckling length is equal by the distance between the brace points.
This Guidance Note covers the attachment of bracing members and cross girders to main I girders, usually achieved by means of connections to stiffeners or cleats on the web of the girder. The details are representa- tive of details that are used in practice, but are not the only details that are suitable in all cases.
Three straight steel I-girder bridges Little or no skew Basic design parameters: • Six units, mix of 2-and 3-span units • Spans: 113’ to 164’ • Girder spacing: 9’-4” to 10’-9” • Girder web depths: 62” to 74” • Cross-frame spacing: 21’ to 25’ 20 9/14/2017
Bracing systems serve a number of important roles in both straight and horizontally curved bridges. The braces provide stability to the primary girders as well as improving the lateral or torsional stiffness and strength of the bridge system both during construction and in service.
Lateral bracing can be divided into four categories: rela-tive, discrete (nodal), continuous and lean-on. A relative brace system controls the relative lateral movement between two points along the span of the girder. The top flange horizontal truss system shown in Figure 4 is an example of a relative brace system. The system relies on
