Recently I have been doing a structure simulation on ABAQUS, which is about cutting a portion of the beam flange. and i found the load capacity has been increased compared with the normal beam connection section. I dont have any civil engineering on-site experience. did anyone know what is the theory behind this?
The wheeze of cropping the flanges in the manner that your figure shows is something I have seen before and causes me some concern since it begs the question why would one wish to weaken a structural member in this fashion. I think the idea behind this is that in doing so, the relative strength of the joint or connection can be made greater than the beam. It does of course depend on the worst moment in the beam being seen at the connection. So if the structure is loaded to collapse the beam will develop a plastic hinge before the bolts pop out of the connection. The idea that connections should be some factor stronger than the incoming members is codified in some of the British Standards and possibly further afield.
Now you say that your FE model is predicting a greater load capacity for the beam after it has been waisted? This doe not immediately make sense but it might be down to your FE model rather than fact. I wonder if you can provide more details regarding your model. Loads, supports, non-linear material properties etc. Also the mesh you have used is appalling and I would not really expect sensible results from such a mesh. It is a simply shape to mesh with a structured mesh of hexahedra and this would give you a much better result.
Dear Ramsay,
thank you for your reply, your opinion are really useful.
the load and boundary condition for both of these models are the same.and the mesh is different only at the flange cut part. I am using displacement control instead of load control in the software. the max load of the flange cut model at the edge of the H beam is twice as great as the normal model.
I need to see a diagram of how you are supporting and loading the beam. Also are you using a non-linear material model and running until you develop a plastic hinge?
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