Hi all

I am modelling a 4-point bending analysis of a composite decking floor system. There are large contact areas between the sandwiched decking and the ceiling and top boards, I have tried both contact modelling approaches (using contact pairs and general contact with most default options) but get convergence issues, "SDI" with too many discontinues iterations caused by over-closures and openings. I am also having trouble modelling the fixities that I used in my experiment to fix the boards to the decking (45mm Self-drilling screws used to fix boards to the decking on top and bottom),I connected nodes in the model using attachment lines through the different layers and assigned connector sections to it, what connector section type should I use or am I using the wrong approach? I get a 'There are unconnected regions in the model' error as well. below are attached photos and obj model file. 

Any help would be much appreciated.