Calibration of Live-Load Factor in LRFD Bridge Design Specifications Based on State-Specific Traffic Environments
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VIEW CORRECTIONPublication: Journal of Bridge Engineering
Volume 16, Issue 6
Abstract
In this paper, the live load factor in the Strength I Limit State in the AASHTO LRFD Bridge Design Specifications is calibrated based on state-specific traffic environments and bridge configurations. As the initial development of the live load factor in the LRFD specifications was intended to be applied at the national level, state-specific traffic conditions, such as traffic volume, truck load, or bridge configurations, were not considered in the development process. In addition, due to the lack of reliable U.S. truck weight data in the early 1990s, truck data from Ontario, Canada, collected in the 1970s were used for the initial AASHTO calibration. Hence, the application of the live load factor in the LRFD specifications may result in over- or under-designed bridges for a specific state. Through reliability analysis of bridges based on state-specific traffic and bridge conditions, the live load factor can be recalibrated to achieve both reliable and economical bridge design. In this study, the traffic data collected for 5 years at weigh-in-motion stations in Missouri are used to simulate realistic truck loads. In addition, typical bridge configurations identified from statistical analyses of 2007 National Bridge Inventory are used to define representative bridges in Missouri. Reliability analysis results using the weigh-in-motion data and the representative bridge configurations show that most bridges have reliability indexes higher than 3.5. Live load calibration factors for the design of new bridges in Missouri are proposed as a function of the bridge’s average daily truck traffic.
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Acknowledgments
This study was funded by the Missouri Department of Transportation (MOTIMoDOT) and Missouri S&T National University Transportation Center (UNSPECIFIEDNUTC). All findings and conclusions are those of the writers and do not represent MoDOT or NUTC.
References
American Association of State Highway and Transportation Officials (AASHTO). (2007). AASHTO LRFD bridge design specifications, 4th Ed., Washington, DC.
Ang, A. H. S., and Tang, W. H. (1984). Probability concepts in engineering planning and design: Decision, risk and reliability, Vol. 2, Wiley, New York.
Box, G. E. P., and Wilson, K. B. (1951). “On the experimental attainment of optimum conditions.” J. R. Stat. Soc. Ser. B, B13, 1–38.
Chang, M. S., and Kim, Y. K. (2000). “Development of capacity estimation method from statistical distribution of observed traffic flow.” Proc., 4th Int. Symp. on Highway Capacity, Transportation Research Board, Maui, HI, 299–309.
Cowan, R. J. (1975). “Useful headway models.” Trans. Res., 9(6), 371–375.
Fu, G., and Van de Lindt, J. W. (2006). “LRFD load calibration for state of Michigan trunkline bridges.” Rep. RC-1466, Michigan Dept. of Transportation, Lansing, MI.
Gumbel, E. J. (1958). “Statistics of extremes.” Columbia Univ., New York.
He, M., Liu, X., and Rong, J. (2002). “Driver’s preferred time headway selection: Experimental findings.” Proc., 3rd Int. Conf. on Traffic and Transportation Studies, ASCE, Reston, VA.
Hwang, E. S., and Nowak, A. S. (1991). “Simulation of dynamic load for bridges.” J. Struct. Eng., 117(5), 1413–1434.
Kulicki, J. M., Prucz, A., Clancy, C. M., Mertz, D. R., and Nowak, A. S. (2007). “Updating the calibration report for AASHTO LRFD code.” Final Report, Project No. NCHRP 20-7/186, Transportation Research Board of the National Academies, Washington, DC.
Kwon, O., Kim, E., Orton, S., Salim, H., and Hazlett, T. (2010). “Calibration of the live load factor in LRFD design guidelines.” Project 2a Report, Missouri Dept. of Transp., Jefferson City, MO.
Nowak, A. S. (1999). “Calibration of LRFD bridge design code.” NCHRP Report 368, Transportation Research Board and National Research Council, Washington, DC.
Pratim Dey, P., and Chandra, S. (2009). “Desired time gap and time headway in steady-state car-following on two-lane roads.” J. Transp. Eng., 135(10), 687–693.
Sivakumar, B., Ghosn, M., and Moses, F. (2008). “Protocols for collecting and using traffic data in bridge design.” Transportation Research Board and National Research Council. 〈http://www.trb.org/Main/Blurbs/165399.aspx〉 (Jun. 15, 2009).
Van de Lindt, J. W., Fu, G., Zhou, Y., and Pablo, R., Jr. (2005). “Locality of truck loads and adequacy of bridge design load.” J. Bridge Eng., 10(5), 622–629.
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Published In
Journal of Bridge Engineering
Volume 16 • Issue 6 • November 2011
Pages: 812 - 819
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Aug 4, 2010
Accepted: Dec 10, 2010
Published online: Dec 13, 2010
Published in print: Nov 1, 2011
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