Parametric Study of Skewed Steel I-Girder Bridge Truck Live Load Response
Publication: Journal of Bridge Engineering
Volume 29, Issue 12
Abstract
Skewed steel I-girder bridges experience complex load distribution under live load that is not thoroughly understood, while standard design practice for such bridges consists of simplifications that should be further evaluated and verified. Commonly used line girder analysis (LGA) can estimate strong-axis bending stress through the application of a live load distribution factor (LLDF) that considers the skew effect from 30° to 60°, and it accounts for skew-related lateral response by simply adding a flange lateral bending stress for skew exceeding 20°. Since LGA calculations related to skew do not account for bridge width, and because girder lateral bending response is considered in a simplified fashion, further refinement may be possible. In addition, the widely used practices of designing exterior and interior girders with the same demand and analyzing stub and integral abutment bridges in a similar way need to be further assessed. This paper evaluates the effect of bridge geometric parameters—including skew of 0°–70°, bridge width ranging from 8 to 26 m (27–84 ft), and abutment type (stub versus integral)—on skewed steel I-girder bridge response through a numerical parametric study (using field-validated models), considering live load positioning across the width of a bridge. The distribution of girder strong-axis and lateral bending stress was analyzed, with peak stress compared to LGA calculations. Exterior girders were generally observed with larger strong-axis bending stress but smaller lateral bending stress (versus interior girders) when directly loaded; estimating girder strong-axis bending stress using LGA with a controlling LLDF for all girders can be overly conservative for interior girders. The distribution of strong-axis and lateral bending stress on a skewed bridge with either stub or integral abutments was also found to be dependent on live load positioning, with peak stress closer to bridge obtuse corners (away from bridge midspan) as skew increases. The standard practice of providing a minimum distance between the bridge end and the first intermediate cross-frame was confirmed to be important to avoid lateral bending stress concentration near bridge obtuse corners. Girder response near the bridge pier was generally less significant than that along bridge spans under live loading, except for exterior girder flange lateral bending stress. Near the pier, bottom flange lateral bending stress increases with increasing skew, while interior and exterior girders behave differently under the skew effect for strong-axis bending stress.
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Data Availability Statement
All data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This paper documents a portion of the work done for project ICT R27-194 (“Evaluation of Spatial and Temporal Load Distribution in Steel Bridge Superstructures”). ICT R27-194 is being conducted in cooperation with the Illinois Center for Transportation (ICT); Illinois Department of Transportation (IDOT), Division of Highways; and the US Department of Transportation, Federal Highway Administration (FHWA). The contents of this paper reflect the view of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the ICT, IDOT, or FHWA. The authors would like to thank the members of the project Technical Review Panel, chaired by Mark D. Shaffer of the Illinois Department of Transportation, for their valuable assistance with this research.
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Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 29 • Issue 12 • December 2024
Copyright
© 2024 American Society of Civil Engineers.
History
Received: Jan 11, 2024
Accepted: Jul 11, 2024
Published online: Sep 19, 2024
Published in print: Dec 1, 2024
Discussion open until: Feb 19, 2025
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