Stress Concentration Factor with FEM

[salmarigliano]

Good Day All,

I need your advice on the following:

I am assessing a frame made mostly with H beams and braces with gusset plates connections. My client is asking to assess all the connections for fatigue, but I cannot find any typical stress concentration factor for H beams connections (beam to column web / beam to columns flange, butt connection etc) and pipes with gussets on regulations and standards. I am trying to determine the values through FEM analysis, but I would need some guidance on that. For the moment, I have tried to assess it through DNV Framework, but it gives me failure for fatigue even with SCF = 1. In that case, the typical connection would need to be redefined adding brackets or reviewing the shape etc. In that case, will the SCF of the revised connection be lower than 1 or in no case that can happen? DNV RP C203 gives the SCF only for the tubular joints or plated structures.

Many Thanks.

 

[jayrod12]

What does the frame support?

What kind of loading?

 

[salmarigliano]

The frame is to be used offshore on a topside and supports equipment which are fixed. The fatigue loads are due to the environmental load only, hence vessel accelerations and prescribed displacement from ship bending.

 

[WARose]

Are you sure this condition doesn't fall under one of AISC's loading scenarios (see Appendix 3 of AISC 13th edition)?

 

[salmarigliano]

I guess I misunderstood the calculation to be performed. I think if we use the DNV SN-Curves they should include already the SCF for the geometry and the allowable stress range should be compared to the nominal stress. Is that correct?