1. Here is a beam and surface that share topology from SpaceClaim. The nodes along the beam and surface are shared which simulates a beam with a full length weld to the surface.

The beam and surface are manually offset in Mechanical to give the proper appearance, which does affect the calculation.

2. When the solid cylindrical wall has a Midsurface operation, that pulled the surface away from the solid on the inside. The solid on the inside will not be connected to the wall once the geometry is opened in Mechanical.