luence exactly how loads are distributed.Where defining a precise mathematical model of what happens to a bridge load in astructure is complicated, it is possible to examine the variables which influence thedistribution. The influencing parameters are a function of the bridge superstructurecross-sectional properties. The following parameters determine how loads are distributedin a bridge superstructure. It should be kept in mind that this is a general list and thatother variables could potentially affect the distribution on loads. With this in mind, theinfluencing parameters are* Type of floor* Spacing between stringers* Spacing of secondary members* Stiffness of primary members* Stiffness of secondary members* Type of bracing employed (if any)* Size and position of loadsTable 1.3 shows the AASHTO wheel load distribution factors for various floortype and spacing configurations. Distribution will also vary depending on whetherlongitudinal or transverse members are being analyzed. It is important to note that thesefactors are applied to wheel loads. When computing the bending moment due to the LL, afraction of both the front and rear wheel loads is taken to act on a given interior stringer. Consulting table 1.3(4), for concrete deck with two or more lanes and a stringer spacingof less than 14 ft, the resultant distribution factor will beDF = S/5.5 = 7.0 ft/5.5 = 1.27Eq. 7This value would be multiplied by half the weight of the design truck. The totalweight of an H20-44 truck is 8,000 lb. (front axial) + 32,000 lb. (rear axle) or 40,000 lb. Therefore, one set of from and rear wheels would be half this amount or 20,000 lb. or 20kips. When computing bending moments the distributed load used would be(2)Distributed Load = DFOne set of wheels= 1.2720 kips = 25.4 kipsThis means that 25.4 kips of the 40 kip H20-44 truck acts on any given interiorstringer and the remaining 14.6 kips are distributed amongst the other girders. If thespacin...
