AASHTO-LRFD Live Load Distribution for Beam-and-Slab Bridges: Limitations and Applicability
Publication: Journal of Bridge Engineering
Volume 12, Issue 6
Abstract
This paper presents a comparison between the live load distribution factors of simple span slab-on-girders concrete bridges based on the current AASHTO-LRFD and finite-element analysis. In this comparison, the range of applicability limits specified by the current AASHTO-LRFD is fully covered and investigated in terms of span length, slab thickness, girder spacing and longitudinal stiffness. All the AASHTO-PCI concrete girders (Types I–VI) are considered to cover the complete range of longitudinal stiffness specified in the AASHTO-LRFD. Several finite-elements linear elastic models were investigated to obtain the most accurate method to represent the bridge superstructure. The bridge deck was modeled as four-node quadrilateral shell elements, whereas the girders were modeled using two-node space frame elements. The live load used in the analysis is the vehicular load plus the standard lane load as specified by AASHTO-LRFD. The live load is positioned at the longitudinal location that produced the extreme effect, and then it is moved transversely across the bridge width in order to investigate all possibilities of one-lane, two-lane and three-lane design loads. A total of 886 bridge superstructure models were built and analyzed using the computer program SAP2000 to perform this comparison. The results of this study are presented in terms of figures to be practically useful to bridge engineers. This study showed that the AASHTO-LRFD may significantly overestimate the live load distribution factors compared to the finite-element analysis.
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Acknowledgments
This research was supported by Bradley University and the International Road Federation. This financial support is highly appreciated.
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Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 12 • Issue 6 • November 2007
Pages: 765 - 773
Copyright
© 2007 ASCE.
History
Received: Dec 28, 2005
Accepted: Oct 4, 2006
Published online: Nov 1, 2007
Published in print: Nov 2007
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