Hi.

I created a 3d i-section beam to check the moment at the centre. The images show type of loading which i wanted to check. 

Both the ends of the beam are fixed (ENCASTRE) and the entire beam length (8000mm) is loaded with a UDL of 20 N/mm.

For the 3d model, the surfaces at the ends of the beam have a kinematic coupling to a reference point and the top surface has nodes coupled to another reference point for UDL. Due to this, the node at the corner is common to two cuplings and so an error of over constraint checks is there. 

How shall I rectify my model?