The live load distribution factors contained in the AASHTO-LRFD Bridge Design Specification present a major change to the AASHTO-LFD specifications that have been in effect for more than 50 years. This change has generated some interest in the bridge engineering community and has raised some questions as well. The AASHTO-LFD formulas are based on the girder spacing only and are usually presented as S/D, where S is the spacing and D is a constant based on the bridge type. This method is applicable to straight and right (nonskewed) bridges only. The new formulas are more complex and consider more parameters, such as bridge length and slab thickness. It may not be obvious to the engineers what added accuracy and flexibility is gained by the increased complexity. This paper will present the background on the development of the formulas and compare their accuracy with the S/D method. A discussion on the extension of the single girder design (using formulas) to skewed bridges is also presented.


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  • Accession Number: 00794564
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 21 2000 12:00AM