Calibration of Temperature Gradient Load Factor for Service Limit State Design of Concrete Slab-on-Girder Bridges
Publication: Journal of Bridge Engineering
Volume 27, Issue 11
Abstract
Design factors in load and resistance factor design (LRFD) codes are determined using structural reliability theory to account for the uncertainties in loads and resistance. The calibration of load factors for strength limit states has been investigated during the development of AASHTO LRFD bridge design specifications (BDS). In comparison, sparse efforts can be found for calibrating service limit state load factors. Temperature variations affect all types of bridges and cause additional stresses, deformations, and moments in different bridge components. Calibration of load factors for vertical temperature gradients appear to be lacking for both strength and service limit states. This paper focuses on calibrating positive vertical temperature gradient load factors for the Service III limit state. A design space consisting of 70 two-span continuous bridges with different bridge configurations is established and designed for severe corrosive exposure conditions. Design stresses for various load cases are first calculated. Using the first-order reliability method (FORM) and considering the sources of uncertainties due to materials, fabrication, and load effects, temperature gradient load factors were then calibrated for different risk levels. The results show that vertical temperature gradient load factors between 1.00 and 1.40 should be used for the Service III limit state.
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Acknowledgments
This research is sponsored in part by the National Science Foundation, USA (IUSE# 1432397) and the Louisiana Transportation Research Center (Project # 12-1ST) in addition to support from the Department of Civil and Environmental Engineering at Louisiana State University. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors.
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Published In
Journal of Bridge Engineering
Volume 27 • Issue 11 • November 2022
Copyright
© 2022 American Society of Civil Engineers.
History
Received: Jan 19, 2022
Accepted: Jul 20, 2022
Published online: Sep 15, 2022
Published in print: Nov 1, 2022
Discussion open until: Feb 15, 2023
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