American Society of Civil Engineers


State-Specific LRFR Live Load Factors Using Weigh-in-Motion Data


by Jordan Pelphrey, (Grad. Res. Asst., School of Civ. and Constr. Engrg., Oregon State Univ., Corvallis, OR 97331), Christopher Higgins, (corresponding author), M.ASCE, (Assoc. Prof., School of Civ. and Constr. Engrg., Oregon State Univ., Covallis, OR 97331 E-mail: chris.higgins@orst.edu), Bala Sivakumar, M.ASCE, (Chf. Engr., Lichtenstein Consulting Engrs., Inc., 45 Eisenhower Dr., Paramus, NJ 07652), Richard L. Groff, (Sr. Load Rating Engr., Bridge Sec., Oregon Dept. of Transp., 355 Capitol St. NE, Salem, OR 97301), Bert H. Hartman, (Bridge Program of Unit Managing, Bridge Sec., Oregon Dept. of Transp., 355 Capitol St. NE, Salem, OR 97301), Joseph P. Charbonneau, (Local Agency Load Rating Engr., Bridge Sec., Oregon Dept. of Transp., 355 Capitol St. NE, Salem, OR 97301), Jonathan W. Rooper, (Load Rater, Brige Sec., Oregon Dept. of Transp., 355 Capitol St. NE, Salem, OR 97301), and Bruce V. Johnson, (State Bridge Engr., Bridge Sec., Oregon Dept. of Transp, 355 Capitol St. NE, Salem, OR 97301)

Journal of Bridge Engineering, Vol. 13, No. 4, July/August 2008, pp. 339-350, (doi:  http://dx.doi.org/10.1061/(ASCE)1084-0702(2008)13:4(339))

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Document type: Journal Paper
Abstract: The LRFR Manual, within commentary Article C6.4.4.2.3, contains provisions for development of site-specific live load factors. In Oregon, truck weigh-in-motion (WIM) data were used to develop live load factors for use on state-owned bridges. The factors were calibrated using the same statistical methods that were used in the original development of LRFR. This procedure maintains the nationally accepted structural reliability index for evaluation, even though the resulting state-specific live load factors were smaller than the national standard. This paper describes the jurisdictional and enforcement characteristics in the state, the modifications used to described the alongside truck population based on the unique truck permitting conditions in the state, the WIM data filtering, sorting, and quality control, as well as the calibration process, and the computed live load factors. Large WIM data sets from four sites were used in the calibration and included different truck volumes, seasonal and directional variations, and WIM data collection windows. Finally policy implementation for actual use of the factors and future provisions for maintenance of the factors are described.


ASCE Subject Headings:
Load factors
Live loads
Bridge maintenance