Our firm has been selected to design an overpass as part of a highway expansion project. The elevation of the roadway is set to match the grade of the other lanes. To provide adequate height clearance...

Our firm has been selected to design an overpass as part of a highway expansion project. The elevation of the roadway is set to match the grade of the other lanes. To provide adequate height clearance below the overpass, we need to use relatively shallow members. An experienced member of the team recommends we use deeper members for the outside spans to draw moment away from the shallower interior spans. We are in the preliminary design phase, so that experienced engineer suggests we start by assuming that the exterior spans have moments of inertia double those of the interior spans. The cross-sectional areas for the different spans will be essentially equal. Our task is to find the peak moment in each span due to dead load.