Hello tjasaa,
You can use Patch to create a 2D dynamic 2D object you have to put on each your beams :
https://helpcenter.graphisoft.com/user-guide/88762/
Or you are able to use a complex profile by drawing a cross into your element :
Christophe - FRANCEArchicad Designer and Teacher
Archicad 15 to 27 FRA FULL
OS 11.6 Big Sur - MacBook Pro 2017 - 16Go RAM
"Quality is never an accident ; it's always the result of an intelligent effort" John Ruskin