g between the stringers had been greater than 14 ft, the concrete deck between thetwo adjacent interior stringers would be assumed to act as a simple beam. The wheelloads would then act on this simple beam and the resulting reactions taken as the load onany individual stringer. If the bridge were carrying only one design traffic lane, then thedistribution factor would have been S/7.0 rather than S/5.5.(2)In addition to floor type and stringer spacing, the criteria governing loaddistribution vary depending on the orientation of the member being analyzed and itsposition. The following offers a general overview of some of the major types of floorsystems and the related AASHTO requirements for distribution of loads.As discussed before, the live load distribution factor is determined from table 1.3. This accounts for lateral distribution of loads only. No longitudinal distribution of wheelloads is allowed. Live load bending moments are computed using on set of front and rearwheels multiplied by the distribution factor.Unlike an interior girder, outside girders are often subject to dean loads over andabove those caused by the deck and superstructure frame. Loads such as curbs,sidewalks, railings, barriers, etc., which are placed on an exterior girder can be distributedequally among primary members. For slab-on-stringer bridge with four or more stringers,the following distribution factors are used(1)DF = S/5.5 (S( 6 ft) or DF = S/ (4.0 + 0.25S) (6(S(14ft)Where S = distance between exterior and adjacent interior stringerFrom that equation it is shown that the distribution factor will vary depending onthe spacing of stringers. As is the case with many interior stringers, when the spacingbetween an exterior and adjacent interior stringer exceeds 14 ft, the flooring between thetwo stringers is taken to act as a simple beam with the load on each stringer being theresulting wheel load reaction. This is also the general load distrib...
