Josh Brighton, Instructor

Engineering design and Graphics

School of Engineering Technology and Commonwealth Engineering

The Pennsylvania State University

ABSTRACT

The 1994 AASHTO LRFD Bridge Design Specifications and Penn DOT DM-4 contain equations for live load distribution factors for various bridge types, however, a double cell box girder falls outside the range of applicability for the distribution factor equations specified in the codes. Live load distribution factor criteria for adjacent double cell box beam girder bridges were developed. Eighteen different right bridges and three different skew bridges were modeled as grillages. The grillage meshes were loaded with the standard AASHTO design truck and analyzed using a structural analysis software package. Distribution factors for all bridges modeled in the study were developed from the moments and shears determined from the computer analysis. Extrapolated distribution factors were calculated for all bridges based on distribution factor equations specified in AASHTO LRFD and DM-4 distribution factors divided by the distribution determined from the grillage analogy were calculated for all of the bridges in the study. This was done to determine if the distribution factor equations specified in AASHTO LRFD and DM-4 could be directly applicable to the cross-section considered in the study. From this, it was found that many of the AASHTO and DM-4 distribution factor equations are directly applicable to adjacent double cell box beam girders. However, some AASHTO and DM-4 distribution factor equations require correction factors for application to double cell girders.