Structural question about JTS

[jsmith86]

JTS is fine. If I had to guess, I'd say that they have inspectors check everything out pretty regularly. Also, any of you who question JTS have obviously never been in the basement of Kinnick.

[majorcyfan]

The top floors of some skyscrapers can sway back n forth in the wind up to 5' (2.5' either direction).

Back when the World trade Center opened, our national sales group stayed at the hotel that went down and ate at the restaurant at the top of one of the towers.

We lined up salt and pepper shakers with lights from other buildings below us, we were sitting at the outside near some of the windows, and laughed at how much sway we observed from plotting a line withe the salt and pepper shakers. The restaurant revolved, but did not that night, so we could somewhat measure the swaying of the building. Scary to think how much it really swayed.

[besserheimerphat]

I've heard that the floors in houses are also designed based on rigidity rather than strength. A 2x10 joist and plywood can hold a hell of a lot of weight, but the "on center" spacing depends on how much you mind the dishes rattling when you walk across the floor.

[Sousaclone]

One of the CE professors (Klaiber, I believe) and some grad students actually did a research project on the deflection of the upper deck at one point. I don't remember all the details but it's fine.

I don't remember how exactly the upper decks are framed, but those at the very top and very bottom would be most likely to notice the vibrations as they are at the ends of the cantilevers and would see the most movement.

[Cyclone90]

I've been going to games at JTS since I was a student in the mid/late 80s. IMO, the upper deck is moving more than it use to. The fans are more into it now a days and the sound system sure rocks, so that could contribute to it I guess, but it still gives me the creeps. It moves more than I'm comfortable with. I'd certainly have it checked out. A stadium collapse is not something we'd like to be known for.

[Cyclone90]

Also curious who built and designed JTS and what it's life expectancy was at the time.

I hope it's in better shape than Hilton's exterior steps and walkways, because they're falling apart too. All of the JTS structure was exposed to the elements for a long time before we started adding things.

[ISUSammu]

One of the CE professors (Klaiber, I believe) and some grad students actually did a research project on the deflection of the upper deck at one point. I don't remember all the details but it's fine.

I don't remember how exactly the upper decks are framed, but those at the very top and very bottom would be most likely to notice the vibrations as they are at the ends of the cantilevers and would see the most movement.

Klaiber and Wipf. I believe they wrote a report that called the motion the "touchdown effect." No issues. Flexibility is OK in structures except when glass and masonry are involved.

[Doc]

One of the CE professors (Klaiber, I believe) and some grad students actually did a research project on the deflection of the upper deck at one point. I don't remember all the details but it's fine.

I don't remember how exactly the upper decks are framed, but those at the very top and very bottom would be most likely to notice the vibrations as they are at the ends of the cantilevers and would see the most movement.

I remember Klaiber talking about it vaguely.

I'll get worried about the upper deck when they start weighing you before you enter the student section.

[Tazzels]

Structural Deflection

1) I believe you will actually get a greater deflection if you load every other span as opposed to all of the spans. So if a beam spans 300 ft and has 7 supports, you will get the greatest deflection by loading between spans 1-2, 3-4, and 6-7.

2) Structures are design to have some allowable movement. There is a difference between being structurally sound and a structure meeting serviceability requirements.

[Tazzels]

Please read the following on structural serviceability. I copied it from wikipedia:

In civil engineering, serviceability refers to the conditions under which a building is still considered useful. Should these limit states be exceeded, a structure that may still be structurally sound would nevertheless be considered unfit. It refers to condition others than the building strength that renders the buildings unusable. Serviceability limit state design of structures includes factors such as durability, overall stability, fire resistance, deflection, cracking and excessive vibration.
For example, a skyscraper could sway severely and cause the occupants to be sick (much like sea-sickness), yet be perfectly sound structurally and in no danger of collapsing. This building is obviously no longer fit for human occupation, yet since it is in no danger of collapsing, the structure would be considered as having exceeded its serviceability limit state.
[edit] Serviceability limit

A serviceability limit defines the performance criterion for serviceability and corresponds to a conditions beyond which specified service requirements resulting from the planned use are no longer met. In limit state design, a structure fails its serviceability if the criteria of the serviceability limit state are not met during the specified service life and with the required reliability. Hence, the serviceability limit state identifies a civil engineering structure which fails to meet technical requirements for use even though it may be strong enough to remain standing.
A structure that fails serviceability has exceeded a defined limit for one of the following properties:

• Excessive deflection
• Vibration
• Local deformation

Serviceability limits are not typically defined by building code developer, government or regulatory agency. Building codes tend to be restricted to ultimate limits related to public and occupant safety. Global geopolitical variations are likely to exist.

[Cyclone90]

Please read the following on structural serviceability. I copied it from wikipedia:

In civil engineering, serviceability refers to the conditions under which a building is still considered useful. Should these limit states be exceeded, a structure that may still be structurally sound would nevertheless be considered unfit. It refers to condition others than the building strength that renders the buildings unusable. Serviceability limit state design of structures includes factors such as durability, overall stability, fire resistance, deflection, cracking and excessive vibration.
For example, a skyscraper could sway severely and cause the occupants to be sick (much like sea-sickness), yet be perfectly sound structurally and in no danger of collapsing. This building is obviously no longer fit for human occupation, yet since it is in no danger of collapsing, the structure would be considered as having exceeded its serviceability limit state.
[edit] Serviceability limit

A serviceability limit defines the performance criterion for serviceability and corresponds to a conditions beyond which specified service requirements resulting from the planned use are no longer met. In limit state design, a structure fails its serviceability if the criteria of the serviceability limit state are not met during the specified service life and with the required reliability. Hence, the serviceability limit state identifies a civil engineering structure which fails to meet technical requirements for use even though it may be strong enough to remain standing.
A structure that fails serviceability has exceeded a defined limit for one of the following properties:

• Excessive deflection
• Vibration
• Local deformation

Serviceability limits are not typically defined by building code developer, government or regulatory agency. Building codes tend to be restricted to ultimate limits related to public and occupant safety. Global geopolitical variations are likely to exist.

Great posts. So what would a college football stadium's serviceability limit be, and have we exceeded it if it's indeed giving people motion sickness.

[Blandboy]

Lots of buildings in quake zones are built like this. They are built to move so that when a quake hits, the building will be able to take a good amount of movement without coming apart. At basic training, our buildings were built like that and when a platoon was getting smoked below us, the entire building would shake. My assumption is that the same type of technique was used at Jack Trice.

Other structures may be built to endure a quake ... but a CYCLONE? I don't think so. There's only one Jack!!!

[madcityCY]

I've been going to games at JTS since I was a student in the mid/late 80s. IMO, the upper deck is moving more than it use to. The fans are more into it now a days and the sound system sure rocks, so that could contribute to it I guess, but it still gives me the creeps. It moves more than I'm comfortable with. I'd certainly have it checked out. A stadium collapse is not something we'd like to be known for.

Yeah, different people have different level of tolerance for movement and vibration, just like temperature, lighting needs, etc. Some folks think its fun, others get very uneasy. That's what can make design difficult at times.

[hawkeyeh8r]

we need to find a new place to build a new stadium. are there any places in ames (perferably near campus) that would make a decent site for a new stadium. hopefully we could still have similar tailgating since thats one thing that we shouldnt lose

[theshadow]

I've been going to games at JTS since I was a student in the mid/late 80s. IMO, the upper deck is moving more than it use to.

The upper deck doesn't move if nobody is up there. [see also Walden, Jim.]