American Society of Civil Engineers


Live-Load Distribution Factors for Prestressed Concrete, Spread Box-Girder Bridge


by Erin Hughs, (Grad. Student, Civ. Engrg. Dept., New Mexico State Univ., P.O. Box 30001/MSC 3CE, Las Cruces, NM 88803-8001) and Rola Idriss, (Prof., Civ. Engrg. Dept., New Mexico State Univ., P.O. Box 30001/MSC 3CE, Las Cruces, NM 88003-8001)

Journal of Bridge Engineering, Vol. 11, No. 5, September/October 2006, pp. 573-581, (doi:  http://dx.doi.org/10.1061/(ASCE)1084-0702(2006)11:5(573))

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Document type: Journal Paper
Abstract: This study presents an evaluation of shear and moment live-load distribution factors for a new, prestressed concrete, spread box-girder bridge. The shear and moment distribution factors were measured under a live-load test using embedded fiber-optic sensors and used to verify a finite element model. The model was then loaded with the American Association of State Highway and Transportation (AASHTO) design truck. The resulting maximum girder distribution factors were compared to those calculated from both the AASHTO standard specifications and the AASHTO LRFD bridge design specifications. The LRFD specifications predictions of girder distribution factors were accurate to conservative when compared to the finite element model for all distribution factors. The standard specifications predictions of girder distribution factors ranged from highly unconservative to highly conservative when compared to the finite element model. For the study bridge, the LRFD specifications would result in a safe design, though exterior girders would be overdesigned. The standard Specifications, however, would result in an unsafe design for interior girders and overdesigned exterior girders.


ASCE Subject Headings:
Box girders
Shear distribution
Moment distribution
Live loads
Finite element method
Field tests
Standards and codes
Bridges