Simplified Live-Load Distribution Factor Equation for Prestressed Concrete I-Girder and Spread Box-Girder Bridges

One of the many changes introduced in the American Association of State Highway and Transportation Officials load and resistance factor design (AASHTO LRFD) is the live-load distribution factor equations. The AASHTO LRFD equations are more accurate than the AASHTO Standard Specification “S-over” equations but they are more complex and take the form of power functions. Furthermore, the equations contained stiffness parameters that are unknown when designing new bridges, thereby allowing the design procedure to be iterative. These complexity and iterative nature are perceived by many practicing engineers as impractical and has raised questions regarding the desired level of simplicity in bridge design calculations. Simplified live-load distribution factor equations for prestressed concrete I-girder and spread box-girder bridges are proposed in this paper. The simplified equations take the form of AASHTO Standard Specification “S-over” equation but in lieu of using constant denominators, the denominators are expressed as functions of girder spacing and span length. Results containing 92 and 54 prestressed concrete I-girder and spread box-girder bridges, respectively, are compared with those from AASHTO LRFD equations. The proposed simplified equations have excellent correlation with the AASHTO LRFD. It is highly recommended that the equation be adopted in future AASHTO LRFD code.

• Supplemental Notes:
  • The title of this paper is listed in the Table of Contents on the CD ROM as Simplified Live-Load Distribution Factor Equation for Prestressed Concrete Girder Bridges.
• Corporate Authors:

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590

  National Concrete Bridge Council

  Portland Cement Association, 5420 Old Orchard Road
  Skokie, IL  United States  60077-1083

  Missouri Department of Transportation

  105 West Capitol Avenue
  Jefferson City, MO  United States  65102

  American Concrete Institute (ACI)

  38800 Country Club Drive
  Farmington Hills, MI  United States  48331
• Authors:
  • Suksawang, Nakin
  • Nassif, Hani H
• Conference:
  • 2008 Concrete Bridge Conference
  • Location: St. Louis MO, United States
  • Date: 2008-5-4 to 2008-5-7
• Publication Date: 2008

Language

• English

Media Info

• Media Type: CD-ROM
• Features: Figures; References;
• Pagination: 12p
• Monograph Title: HPC: Safe, Affordable, and Efficient

Subject/Index Terms

• TRT Terms: Box beams; Box girder bridges; Bridge design; Girder bridges; Load factor; Load transfer; Prestressed concrete; Prestressed concrete bridges
• Identifier Terms: AASHTO LRFD Bridge Design Specifications
• Uncontrolled Terms: I girders
• Subject Areas: Bridges and other structures; Design; Highways; Materials; I24: Design of Bridges and Retaining Walls; I32: Concrete;

Filing Info

• Accession Number: 01104998
• Record Type: Publication
• Files: TRIS, USDOT, STATEDOT
• Created Date: Jul 24 2008 9:28AM