Purpose: Used to change the method for how the program applies distribution factors in Girder System Projects when distribution factors are specified instead of defining lanes. (Not applicable to Line Girder Projects.)
--> Given in girder system input
This command only has an effect When distribution factors are specified (LM-i, LMF-i, LV-i, LVF-i, LD-i for LRFD, or WDS-i, WDR-i, WDF-i, WDD-i for ASD/LFD), however the LOCAL WHEEL DISTRIBUTION ONLY command would not typically be used, as explained below, and if it is to be used then the distribution factors should be determined from a basis other than the line girder type of distribution factors from AASHTO, i.e. the S/5.5 basis in ASD/LFD and the lane fraction formulae for LRFD.
When distribution factors have been specified, use of the LOCAL WHEEL DISTRIBUTION ONLY command causes loading effects for a particular girder to be determined simply by applying the dist. factor for that girder to the influence surface values on the slice of the influence surface along that girder. (Note: since the influence surface values in effect are an influence line that is spread among the girders in the system, influence surface values are lower than what influence line values would be and so the specified dist. factors would need to have this difference somehow taken into account, i.e. the S/5.5 basis for ASD/LFD or the lane fraction formulae in LRFD would generally not be appropriate when the LOCAL WHEEL DISTIBUTION FACTOR ONLY command is used.)
When distribution factors are specified but the LOCAL WHEEL DISTRIBUTION FACTOR ONLY command is not used, the program applies the distribution factors assigned to each girder to the influence surface values on the slice of the influence surface along that girder and then sums the contributions from each girder to determine the live load effect being determined (of a particular location on a particular girder), thereby accounting for the influence surface values being lower than what would be the influence line for that particular girder. This differs from the line girder approach in that the influence surfaces take into account the distribution of loading through the specific framing plan of the system of girders, but otherwise should generally produce live load effects that are consistent with a line girder analysis approach.