Abstract
The current AASHTO load and resistance factor design (LRFD) guidelines are formulated based on bridge reliability, which interprets traditional design safety factors into more rigorously deduced factors based on the theory of probability. This is a major advancement in bridge design specifications. However, LRFD is only calibrated for dead and live loads. In cases when extreme loads are significant, they need to be individually assessed. Combining regular loads with extreme loads has been a major challenge, mainly because the extreme loads are time variables and cannot be directly combined with time invariant loads to formulate the probability of structural failure. To overcome these difficulties, this paper suggests a methodology of comprehensive reliability, by introducing the concept of partial failure probability to separate the loads so that each individual load combination under a certain condition can be approximated as time invariant. Based on these conditions, the extreme loads (also referred to as multiple hazard or MH loads) can be broken down into single effects. In Part II of this paper, a further breakdown of these conditional occurrence probabilities into pure conditions is discussed by using a live truck and earthquake loads on a bridge as an example. There are three major steps in establishing load factors from MH load distributions: (1) formulate the failure probabilities; (2) normalize various load distributions; and (3) establish design limit state equations. This paper describes the formulation of the failure probabilities of single and combined loads.
Similar content being viewed by others
References
AASHTO (1994), LRFD Bridge Design Specifications, 1st ed.
AASHTO (2009), Guide Specifications and Commentary for Vessel Collision Design of Highway Bridges, 2nd ed., 2009.
AASHTO (2010), Guide Specifications for Seismic Isolation Design, 3rd ed., July 2010.
Enright MP and Frangopol DM (1999), “Reliabilitybased Condition Assessment of Deteriorating Concrete Bridges Considering Load Redistribution,” Structural Safety, 21: 159–195.
Ellingwood B, Galambos TV, MacGregor JG and Comell CA (1980), Development of a Probability Based Load Criterion for American National Standard A58, National Bureau of Standards, Washington, DC.
Ferhat Akgul and Frangopol DM (2004), “Timedependent Interaction between Load Rating and Reliability of Deteriorating Bridges,” Engineering Structures, 26: 1751–1765.
Ghosn M, Moses F and Wang J (2003), Design of Highway Bridges for Extreme Events, NCHRP Report 489.
Hida SE (2007), “Statistical significance of Less Common Load Combinations,” Journal of Bridge Engineering, ASCE, 12(3): 389–393.
Kulicki JM (1998), Development of Comprehensive Bridge Specifications and Commentary, NCHRP Report 198, Transportation Research Board of the National Academies, Washington, DC.
Kulicki JM (1999), Design Philosophy of Highway Bridges, Bridge Engineering Handbook.
Kulicki JM, Mertz DR and Wassef WG (1995), Load and Resistance Factor Design for Highway Bridges, FHWA HI-95-0017.
Liang Z and Lee GC (2012), “Towards Multiple Hazard Resilient Bridges: A Methodology for Modeling Frequent and Infrequent Time-varying Loads, Part II, Examples for Live and Earthquake Load Effects,” Earthquake Engineering and Engineering Vibration, 11(3): 303–311.
Lwin MM (1999), Why the AASHTO Load and Resistance Factor Design Specifications? Transportation Research Record Paper No. 99-0935.
Moses F (2001), Calibration of Load Factors for LRFR Bridge Evaluation, NCHRP Report 454, Transportation Research Board of the National Academies, Washington, DC.
Nowak AS (1993), Calibration of LRFD Bridge Design Code, Department of Civil and Environmental Engineering Report, UMIE 92-25, University of Michigan
Nowak AS (1999), Calibration of LRFD Bridge Design Code, NCHRP Report 368, Transportation Research Board of the National Academies, Washington, DC.
Nowak AS and Collins KR (2000), Reliability of Structures, McGraw Hill
Simon F, Bailey, Rolf Bez (1999), “Site Specific Probability Distribution of Extreme Traffic Action Effects,” Probabilistic Engineering Mechanics, 14: 19–26.
Turkstra CJ and Madsen H (1980), “Load Combinations in Codified Structural Design,” ASCE, Journal of Structural Engineering, 106(12): 2527–2543.
Wen YK Hwang H and Shinozuka M (1994), Development of Reliability-based Design Criteria for Buildings under Seismic Load, NCEER-94-0023, State University of New York at Buffalo.
Author information
Authors and Affiliations
Corresponding author
Additional information
Supported by: Federal Highway Administration at the University at Buffalo Under Contract Number DTFH61-08-C-00012
Rights and permissions
About this article
Cite this article
Liang, Z., Lee, G.C. Towards multiple hazard resilient bridges: a methodology for modeling frequent and infrequent time-varying loads Part I, Comprehensive reliability and partial failure probabilities. Earthq. Eng. Eng. Vib. 11, 293–301 (2012). https://doi.org/10.1007/s11803-012-0122-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11803-012-0122-4