I have tried the Shell elements on the steel girders.
Now, I am importing pressures on the girders' surfaces. There are presures on both sides of each girder, but if I transform the solid to a Shell element, it detects the Shell elements as a single surface, and therefore only pressures of one side of the 3D solid are transfered.
In the following image only Girders (1 to 4) are shown. Depending on how Shells are created, upstream or downstream pressures of the solid are therefore transmitted to the shell, ignoring the other side.
Is there anyway to transfer the pressures on both sides?