regulations and gmp for weld resistance with fem

[ilfrau]

Hello everyone,
recently asked me to check the resistance of a lifting equipment through European standards Eurocode 3 for steel structures.
the structure in question is a welded frame mainly formed by square-section tubular bars.

I would like to ask two questions:

1. as it is necessary to make a relationship with all the calculations "as you did at school/university", I would ask you whether it is lawful to use a fem for the sole calculation of the forces along the rods, then using such forces for calculations by hand of the resistance of the individual welded areas. All this by attaching to the report how the forces which are discarded on the joints of the fem were obtained.
2. If you want to use only a fem, in case a verification is not required according to Eurocode 3 legislation, is there a regulation that regulates the fem analysis of welded structures or not?
   For example: Should welding cords be shaped or not in the fem?
   I looked a lot on the internet but I couldn't take away my doubts because there's something about it and someone else.

razie
salute

 

[essebi]

the ec3 is based on the "design by rule" i.e. it serves for the design of the structure. is not made to be used as a tool of "design by analysis". there are clauses for the use of fem methods but that I remember only about plates and shells. However if you make a structure rods and knots to get the forces to knots and internal actions do nothing but apply the science of construction and this is lawful.

 

[ilfrau]

Thank you for answering the first question.
but that you know there are no rules or "authoritative" guidelines for the use of fem for the resistance of welds?
I found only works done by researchers on behalf of third parties, but nothing official.

 

[meccanicamg]

the problem of welding is always a big question. If you have full penetration welds with alloys equal to the base metal you can say that the fem sees a all-united multibody part without interconnection and this is adherent to reality. If the welds are not fully penetrating and are only angle strings it is good that they are modeled because if you have a 40 mm thick plate and the balance with two strings with a=10 you have no prior penetration, the effort is known, the resistance as well but it is easy that the bendings are not correct, so it is good to shape them. I don't think there's anything official around. so little useful theory, many indications where the fem is not absolute reality and should be interpreted.

 

[essebi]

I know that there are nafems courses on the joints in the fem, it is not exclusive to the welding but we also talk about riveting and gluing