I am modeling RC arch culvert in STAAD PRO and I am interested in obtaining the shear force and bending moment values. This is a buried structure. I input the lateral earth pressure and vertical load due to backfill as trapezoidal load on the member segments. the support conditions are hinged. when I analyzed the structure and checked the shear force diagram under self weight, I could not be convinced with the output. Shear value was the least at the supports and showed sharp change at each of the nodes. Need Help.
Keep in mind that in a true catenary arch under self-weight, the shear and bending is essentially zero as the force is carried almost exclusively by axial compression. Since your arch is kinked you'll see some spikes in the force diagrams near these joints, but the magnitude of those are still pretty small relative to the axial force.