Ahmed,
I guess it this point it is time to ask yourself, "How is this going to be actually built?" and model it that way. Obviously a beam and a wall cannot occupy the same space in reality so in ArchiCAD a wall will envelope the beam when they do occupy the same space in the program.
Here are some workarounds though:
1. Use the wall tool to make your beam. Put it on its own custom layer and make its cut fill match the slab. The slab/beam cross section will appear as you would like and there is no line showing the wall in the background since walls will join together seamlessly.
2. Use a fill to cover the top of the wall line in the background.
However, as I said at the beginning of this reply, if you model it as it is going to be built, then no workarounds should be necessary as I would be certain that some sort of sheathing will cover the beam in its true construction according to what you are trying to achieve.
That is the trade-off we face in building information modelling:
Either model with the goal of 100% real world accuracy, which can take more time, increases model complexity and file size.
Or model to an acceptable level for the project at hand and then use 2D drafting details to fill in the gaps. This means that technically the model is less accurate but your drawings should be accurate, your files will be smaller and the require less overall time in many cases.
You must weigh the pros and cons for the project at hand and what you find acceptable.
.
Rubia Torres
