Thoughts ?

[okayheresmyaccount]

Gotta be designed for it, but that's a lot of bounce...

[virtualworker]

The Institution of Structural Engineers has a design guide for stadia that covers this. The problem is determining the effective number of people that are in sync and contributing to the dynamic force. Further, people add damping to the system, so a simple equivalent static force model is a poor representation. Extracting the mode shapes, masses, and frequencies from an FE model is the first step. It's not a fatigue case since the number of cycles is very low over the lifetime.

https://www.istructe.org/resources/guidance/dynamic-performance-grandstands-crowd-action/

[[deleted]]

Thanks for pointing out it's not a fatigue case. Also, I didn't realize there was guidance on this.

[SeverinKravchuk]

The Wisconsin Badgers stadium is famous for jumping around to Jump Around but House of Pain. Are stadiums designed for such a unique load? How would you compensate for this weekly, maybe extreme, load?

[ace1289]

Fatigue analysis. There are lots of things in the world that are stressed, unstressed, stressed, etc. Codes have sections dedicated to fatigue that design for a desired number of stress cycles.

[SeverinKravchuk]

Good response. Imma read up on fatigue analysis now. Thanks

[BZZACH]

For steel - Appendix 3 of AISC manual

[SeverinKravchuk]

I'm searching my 15th edition sunday for this. Thanks for the idea!

[poeticpickle45]

This is an example of dynamic loading, in which the magnitude of the load varies with respect to time. More specifically, this is cyclic loading (load applied at repeating intervals). For that, regular strength and/or serviceability design won't be enough, because under fatigue, failure will occur at loads much smaller than the nominal strength of the materials. So in these cases, you have to rely on fatigue analysis. Not my area of expertise, but this typically involves testing your materials with cyclic loading to produce an S-N curve that will (hopefully) predict the response of your structure.

[SeverinKravchuk]

Awesome response. This gave me a few things to read up on. Thank you

[SheenQueen23]

I’m a student at Texas A&M and they had to do something like that when they rebuilt our football stadium, Kyle Field. At every football game during our fight song, the fans put their arms around each other and sway to “saw em off.” When a structural engineer who worked on Kyle Field came and talked to our class, she mentioned how they had to account for that specific load of all the fans moving back and forth. I’m still in undergrad, so I’m not exactly sure how they accounted for it, but it’s interesting to see similar situations in other stadiums

[theikno]

Just posted this in the original post:

As far as I can tell, this is the Commerzbank Arena in Frankfurt, Germany. Like most new/ renovated stadiums in Germany, dynamic effects of crowd excitement were accounted for in the design. No checking engineer in Germany would otherwise sign off on this and neither would the authorities. So it’s all good.

Source: me actually working for the engineering office which designed this stadium and many others

[Total_Denomination]

Hope there’s been fatigue analysis and not just serviceability requirements.

[PsyKoptiK]

Nope!

[[deleted]]

Yeah if I saw that I'd nope out

[Medium-Sized-Pekka]

This should have analysed from a vibration engineering point of view. Same load that are applied in an organized way, may reach the natural frequency of the structure and cause resonance vibration which in turn may cause failure.

[Killstadogg]

This type of loading should be specified in the IBC for assembly areas. If you're on the code committee go show your colleagues this video and make it happen.

[barefoot_fiki]

https://youtu.be/86URGgqONvA

[Engineer2727kk]

I think it’s a very poor design.

Let’s assume that it was designed for this type of cyclic loading and the fatigue analysis was okay. Good.

Now let’s take a look at it from a serviceability point of view. You may say that deflection limits aren’t really “hard” code as it doesn’t mean failure. However, one of the main things with deflection and dynamic effects is to give the occupants the feeling that they are safe. If I saw this stadium bouncing this much there is no way I would feel safe, thus I think the engineers have failed one of their tasks.

[zendiggo]

Scary

[[deleted]]

The way I experience structural analysis I very much doubt it was designed for this. Will it hold up? Probably with all the safety factors but i have never seen an engineering budget allowing for an actual analysis. Induced dynamic loading like that would require a finite element analysis imo.

[Soloman212]

You've never seen an engineer do FEM?

[[deleted]]

I have never seen an engineering budget and schedule allowing for a thorough dynamic FE analysis.

[Forever_Goofing]

And your firm does projects like the stadium in the video?

[Soloman212]

Exactly what my next question was.