I have an extruded tube with internal flanges that run the length of the tube.  The simulation approach I have taken is to use shell elements for tube outer diameter and inner webs.  I have several areas where the internal webs make a T style junction with the outer tube.  I have created split lines at every web interface, and once meshed the nodes appear to be coincident but are not merging because once a load is applied and the model is run the components are flying off into space.  I have the global contact set to bonded, so not sure that is what is going on.  Any tips regarding mesh coincident as it pertains to shells would be much appreciated.