Bracing systems serve several important roles in both straight and horizontally curved bridges. The braces provide stability to the primary girders as well as improve the lateral or torsional stiffness and strength of the bridge system both during construction and in service. Depending on the geometry of the bridge, braces may be designated as either primary or secondary members. This course provides an overview of the design requirements of the braces so that engineers can properly size the members to provide adequate strength and stiffness.
In some situations during construction, the removal of one or more of these bracing members could potentially result in a partial or total collapse of the structure due to instabilities that can develop as a result of the larger unbraced lengths that result from the removal of these members. In cases such as these, the design engineer must recognize the importance of the bracing and design the members accordingly despite their
designation as secondary members.
Topics:
Torsional Behavior of Open and Closed Girders
Lateral Torsional Buckling
Categories of Bracing
Bracing of I-Girders
General Requirements
Cross-Frame Spacing and Proportions
Top and Bottom Flange Lateral Systems
Cross-Frame Forces in Horizontally Curved Girders
Publication Source:
US FHWA
Disclaimer:
This course on Steel Bridge Design is based on FHWA non-restricted publications in the public domain, dating from 2015 to 2016. All subsequent versions of these courses have become proprietary under a "Rights Reserved" restriction by the AISC and are thus not available as public domain courseware. Design principles and methodologies used in this previous version remain relevant and up to date, as of late 2023. To view the latest versions, please visit the AISC download site at: https://www.aisc.org/nsba/design-and-estimation-resources/steel-bridge-design-handbook
