The most common mistakes in connection design and how to avoid them

We picked some of the most common but still not easy-to-understand questions the users of IDEA StatiCa Connection could come to. And we decided to bring answers in this video, to show you how to improve your connection design knowledge to avoid mistakes in your daily work with the software.
Agenda:
What is the correct position of forces?
Which model type is the right one?
Why do I get bolt errors if the 3D scene looks well?
Why can’t I cut or use the splice operation on my stub?
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[@rane5647]

Thanks for explaining from Russia

[@ideastatica_en]

You're welcome.

[@OswarDuque]

INTERESTING, IT IS A GREAT HELP

[@ideastatica_en]

We're glad our video helped!

[@jordanhernadi2157]

The presented example is wrong for the first question. The column is stiff, but if you have a full depth extended beam-to-girder shear tab the eccentricity could be much bigger, while the bolted connection is almost pinned. That means the vertical force will overload the girder by twisting it!

[@smartbuildengineering]

I agree. In the UK, as per SCI P398 Simple Connections guide, the fin plate is an extension of the beam, with 0 bending at the fin-plate:column interface to avoid torsion of the supporting beam.

[@ideastatica_en]

Well, Simple Connections guide is OK, but in reality, there is no 0 bending at the fin-plate: column interface.

[@smartbuildengineering]

@@ideastatica_en Looking at the case of a beam supporting another beam via a fin plate, if 0 shear is assumed to occur at the bolts, the supported beam reaction is eccentric to the supporting beam, inducing torsion into the supporting beam. Unless the global frame analysis and supporting beam design has allowed for this (very unlikely) then there is likely a dangerous disconnect between connection design and frame analysis, and global equilibrium will not be achieved. The low torsional stiffness of a supporting beam and the relatively high stiffness of the fin plate bolt group is such that I would expect the bolts to attract the loads for resisting rotation of the joint. As a result, if designing ‘your way’, the bolts will receive load that they have not been designed for.

[@thepredator6402]

In reality pinned connections does not exist! See Eurocode provisions. You could try FEA to clear the subject for yourself. Here Idea Statica is right.

[@thepredator6402]

@@smartbuildengineering, the p398 is about moment resisting connections not about simple connections. p358, on the other hand, for simple connections, is asking verification of the tension in the bolts, see page 21, as per the Eurocodes. Tension in the bolts for a simple connection means torsion. You could try FEA to clear the subject for yourself, or do test in an controlled environment. Here Idea Statica is right.

[@harrywirtube]

I have the question : the value inserted in LOAD EFFECT (LE), is it for Service Case (SLS) or Ultimate Case (with loading factor, ULS) ? Thank fo the responses.

[@ideastatica_en]

Hello Harry, please check this article: www.ideastatica.com/support-center/different-ways-of-load-definition What you input in the LOAD EFFECTS are the internal forces in a node - these you read in results of your global structural model (whole structure in SAP2000, Robot, etc.). For that reason these forces are already factorized from this global model and you of course can input nodal internal forces from ULS or SLS load combinations, as you wish.

[@RostonMathias]

very informative !! Keep up the good work Cheers!

[@ideastatica_en]

You're welcome.

[@alikamal2602]

In minute 10:45, you show that, by shifting a shear force to the real hinge location, we will have a positive moment at the support. So my question is, will idea statica take this positive moment into a consideration? In other words, will Idea statica involve that weld which connects the stub to the column in design calculation? I mean will idea statica check that can the weld of a stub resist the positive moment that exists due to shifting a shear force to the hinge location? Thank you........

[@ideastatica_en]

Yes, of course the weld is code-checked for the actual forces acting on it, including this moment at this position.

[@alikamal2602]

@@ideastatica_en Thank you so mucn indeed

[@belkahlahamadi3728]

Hello can you perform a bearing connection of a truss with double angles and gusset on multiple combinaisons imported from a structural software thanks

[@ideastatica_en]

Hello, sure you can, please check our sample projects to see some of the real projects examples: www.ideastatica.com/support-center/sample-projects-for-steel-connection-design

[@gilARENASbert]

I have question regarding model type selection between N-Vy-Vz and N-Vz-Vy-My-Mz. In webinar it's said that while using the N-Vy-Vz model type the program consumes some bending moment from the beam. But some value of bending moment remains or what ? How much does it consume, what approach is used inside the program during this type of analysis? I'm asking that because now I'm designing hinged-type connection of the beam and the results are totally different while using this two model types. It would be great if you can take a look at my connection to clear up doubts

[@ideastatica_en]

Please send your question and the connection file to [e-mail]

[@amrabdullah1995]

hello, thanks for the explanation. I have a question please. how do I check the stresses ? IDEA, provides the equivalent stress (Von-Mises) and I define the material based on the uni-axial tensile test multiplied by a safety factor. is it ok to compare both results ? if the equivalent stress is larger than the allowable stresses, then it is unsafe ? and in this case i dont need to check the strain limit given by 5% as per the EC ?

[@ideastatica_en]

"In general, IDEA does not check the stresses directly and does not need to check the stresses directly because it uses reaching of the 5% limit value of the principal membrane strain for checking in accordance with EN 1993-1-5 App. C. par. C.8 (1). If you use user defined material properties with for example a lower fyd, then IDEA automatically adapts the stress strain diagram based on that. The limit value of 5% for the principal membrane strain is still applied by default, it can be changed in the settings but we don't recommend it. The occuring equivalent stresses in IDEA in general cannot exceed the yield stress fyd significantly since the material behaviour is based on the bilineair diagram from EN 1993-1-5 App. C. par. C.6 (the plastic branch does have a slight inclination which is also needed for numerical stability purposes and is also allowed by the norm, that can cause the stress to be a few MPa above fyd but it should not exceed it more than that.)"

[@amrabdullah1995]

@@ideastatica_en thank you for your explaination

[@TotallyMotivationalOfficial]

Im still confused regarding node and bolts when it will be used

[@ideastatica_en]

Hello, please check the articles: www.ideastatica.com/support-center/how-to-define-correct-load-position www.ideastatica.com/support-center/equilibrium-and-supporting-member And another webinar: kzbin.info/www/bejne/bJ_WiqGLepKXqdUsi=No-LhSyUcoWgv6eX Basically, you shift the position of the shear force to match the real conditions - the position of the hinge, and to respect the global structural model. If you design a connection with a hinge (pinned connection) = in your global structural model, there is no moment in the node, only a shear force, then in IDEA StatiCa you set the position of the shear force to bolts (center of rotation in the hinge). If in the global model you have bending moment in the node (semiridig or rigid connection) then you dont move the shear force position in IDEA StatiCa and leave it in the node. In other cases when you want to elaborate and achieve a perfect alignment, you can use the manual set of position of shear force and thus moment diagram shift.

[@TotallyMotivationalOfficial]

@@ideastatica_en thank u ❤️

[@Structure-Dubai]

hi sir, why i get singularity error during analysis?

[@ideastatica_en]

Hello, thanks for a good question. Singularity warning is an analysis stop warning of occurred mathematical nonconformity. This issue is mostly caused by elements not correctly connected to the members. Find out more about it in on our website: www.ideastatica.com/blog/why-did-my-validation-fail

[@thepredator6402]

what about the origin of axes of coordinates when defining bolt groups of inserting dxf stiffening plates. there is no indication of this center of coordinates. very unpleasant! if the stiffening plate has a complicated geometry, one will find himself in a world of hurt. too bad, you did put the work in this.

[@ideastatica_en]

Thanks for the feedback, we will try to improve this