I am trying to model an existing, single span, skewed bridge with several Steel members (Floorbeams, Truss, Stringers). The member spacings and skew makes it difficult to determine the tributary areas and maximum moments due to Live load for the steel members, thus I created plates connected at 4 corner nodes and assigned it a thickness to try and apply the DL and LL from the deck to the steel members.
The problem I currently have is that the beam offsets is creating an unwanted positive moment at the ends of certain members, which I believe is due to the Eccentricity of the member and constraints at the ends.
My questions are:
1) Is it necessary to include the beam offsets? With the exception of the Truss, the bridge is in the XZ plane and is supported by bearings on either side. All loads are applied vertical in the -Y direction.
2) If beam offsets are necessary, could you instead copy all nodes and paste at an elevation, say 2 ft higher (Y+2'), and assign a master slave to the node give you similar results? The surface for the deck would be generated at the nodes with Y+2 and not the actual member nodes.
3) With the skew and beam spacing varying, should the surface of the deck be polygonal instead of quadrilateral?
I am not trying to design or check the deck only trying to check the steel members, so the purpose of the plates generated by the surface is to apply the deadload from the weight of the deck and use STAAD.beava to determine the maximum responses due to LL. I would normally do this with handcalcs, but again, due to the geometry of the bridge I was hoping there would be an easier way to do this. Open to other suggestions on how to achieve this as well.
Thanks in advance for any help,
David