ution approach taken fornon-slab-on-steel stringer bridges.When an exterior stringer is also intended to carry live load, the allowable stressmay increase by 25 percent, provided that the stringer possesses the capacity which wouldbe required even if there were not a sidewalk present. If a load factor design approach isbeing used and the condition exists where sidewalk plus traffic LL controls, a ( factor of1.25 is used in lieu of the 1.67 value specified.(2)The AASHTO specification does not allow for any lateral distribution of loads fortransverse members. When there are no longitudinal members present and the deck issupported entirely by floor beams, the distribution factors are used. The distributionfactors for transverse members are dependent on floor type and the spacing between floorbeams. (1)A multibeam concrete deck can be either conventionally reinforced or prestressed. Precast prestressed concrete panel decks were discussed earlier. Briefly, these types ofdecks consist of concrete panels which run longitudinally and are placed next to oneanother. The panels are connected together with a shear key and lateral bolts.As with other longitudinal members, no longitudinal distribution of wheel loads isallowed. The AASHTO approach takes into account the stiffness of the deck panelsthrough use of a stiffness parameter C is given as(1)C = (W/L)(((I/J)(1 + ()) = (W/L)(KEq. 8Where W= width of entire bridge perpendicular to beams, ftL= Span length taken parallel to longitudinal girders, ftI=Moment of InertiaJ=Torsion Constant(=Poisson's ration (referred to in most texts as v) for concrete, poisson's ratiocan be assumed to be 0.2K=Stiffness ConstantThe boundary within which the stiffness parameter C falls and its value are used to defineparameter D, which is given byD = (5.75 -0.5NL) +0.7 NL(1-0.2C) for C(5 Eq. 9D = (5.75 -0.5 NL) for C ( 5Where NL = Number of Traffic LanesTherefore, like other members, the resultant distribution ...
