Texas A&M Football
Sponsored by

Vertical dynamic deflection of south 2nd deck.

189,374 Views | 648 Replies | Last: 8 yr ago by The Collective
MagnumLoad
How long do you want to ignore this user?
Structural engineer here, Texas PE. With something like 6 minutes left in the LSU game, fans began bouncing in unison to music. I began to feel vertical movement in the 7th row of the south end second deck in synch with the bouncing of the fans. I could see substantial movement of the lower edge (1st row, which is the end of a cantilever truss structure) of the second deck, where it extends out over the upper part of the first deck. The dynamic movement was vertical, I estimate the deflection was at least several inches. Video analysis should be able to determine the actual movement. The differential movement was visibly evident between my location closer to the fixed end of the truss and the cantilever end of the structure. The seating deck is precast concrete which provides good horizontal diaphragm stiffness, but the vertical support structure is steel, specifically a horizontal steel truss structure back to the vertical steel structure at the concourse. The concrete is just mass as far as vertical movement is concerned, and, if near the natural frequency of the structure, movement can amplify increasingly if the forcing function continues, similar to the dynamic response of bridge structures. Fans noticed and stopped bouncing. Had the bouncing continued at the frequency of the music, deflection could have continued to increase, as it had been. The analysis and design of the south endzone structure for dynamic loading should be reviewed.
MarathonAg03
How long do you want to ignore this user?
AG
You came to the right place to voice your concerns. My team and I will get to work immediately with the review you have requested.
97
How long do you want to ignore this user?
AG
Look at high rises built in California for your answers.
MagnumLoad
How long do you want to ignore this user?
I know this is not the best place, but it does get a lot of views. I also intend to send this to the foundation and administration. Not a joking matter.
claydee2
How long do you want to ignore this user?
AG
Not being informed to the highest degree of accuracy...ah screw it.
AggieDruggist89
How long do you want to ignore this user?
AG
Everyone is a fatass!!!
Bunny Ag
How long do you want to ignore this user?
remember when the east side was going to collapse during the Bama game last year because it "moved" during Midnight yell without G Rollie supporting it?
MagnumLoad
How long do you want to ignore this user?
High rise movement is horizontal, and less than the allowable horizontal movement. Vertical movement is much more serious. Also, the east side movement from sawing 'em off, is horizontal, within allowable.
Ridge14
How long do you want to ignore this user?
Engineers
W
How long do you want to ignore this user?
AG
good points
Personal Best
How long do you want to ignore this user?
Franklin Delano Bluth
How long do you want to ignore this user?
AG
Op,

What are your actual concerns of failure?

Main Truss?

Are you calling for review simply because you noticed deflection in a structure?
jdavis97
How long do you want to ignore this user?
AG
OP, please tell me you don't go out in public in A&M gear.
AgOutsideAustin
How long do you want to ignore this user?
AG
Bama fan wrong holed the whole SEZ!
suburban cowboy
How long do you want to ignore this user?
AG
Can this be blamed on the Bama guy's welds?
MagnumLoad
How long do you want to ignore this user?
I do go out in public in Aggie gear, and also have extensive experience with dynamic analysis and design. My concern was that the movement was visibly increasing in frequency until the bouncing died down. Reason for concern and at least reviewing in light of the design parameters. What frequency range for a vertical forcing function was analyzed?
claydee2
How long do you want to ignore this user?
AG
What's the frequency, Kenneth.
Shake and Bake
How long do you want to ignore this user?
pagina uno?
Philip J Fry
How long do you want to ignore this user?
AG
quote:
High rise movement is horizontal, and less than the allowable horizontal movement. Vertical movement is much more serious. Also, the east side movement from sawing 'em off, is horizontal, within allowable.


Great to know that building in CA aren't designed to withstand Rayleigh waves.
MagnumLoad
How long do you want to ignore this user?
They are designed to do so. The horizontal swaying is ok within allowable. Differential vertical movement is more serious. It may be ok, but should be looked into. If deflection is increasing in tune with the forcing function until the forcing is removed, that is concerning to me. There is not a lot of damping in steel structures.
claydee2
How long do you want to ignore this user?
AG
Great, just great. Now our stadium sucks to.
MagnumLoad
How long do you want to ignore this user?
The north zone support structure is reinforced concrete of considerable mass and stiffness. Much more mass than provided by the south end deck only concrete. Mass is in the denominator for calculating amplitude of response.
trickplay
How long do you want to ignore this user?
I can't believe the company who built the structure didn't have several engineers study this design. That's a real black eye for them and the university.
Philip J Fry
How long do you want to ignore this user?
AG
quote:
They are designed to do so. The horizontal swaying is ok within allowable. Differential vertical movement is more serious. It may be ok, but should be looked into. If deflection is increasing in tune with the forcing function until the forcing is removed, that is concerning to me. There is not a lot of damping in steel structures.


I would be very surprised if the structural engineers who built the stadium did not consider resonances in their analysis.
MagnumLoad
How long do you want to ignore this user?
Probably did consider it, but was it done adequately for the dynamic force of people jumping up and down in synch with music? This is forced response, not just natural frequency analysis. May be ok, but worth a look. It was very unusual.
giddings_ag_06
How long do you want to ignore this user?
AG
So is the stadium going to crumble to pieces or not?! This is a determining factor in renewing season tickets!!
JJxvi
How long do you want to ignore this user?
AG
I don't know if it's going to crumble to pieces but it is somewhere between thrilling and scary to be on that deck. If you're looking out at the field over the lip you can easily see the edge moving up and down several inches.
Philip J Fry
How long do you want to ignore this user?
AG
Thats why I said resonance and not natural frequency. We have plenty of data from the old Kyle field to estimate what kind of dynamic forces we see during the game.
MagnumLoad
How long do you want to ignore this user?
I plan on renewing, but I do think it would be prudent to review that part of the design for vertical dynamic forcing.
FreezeTag
How long do you want to ignore this user?
AG
I was in the first deck high up in the South East corner for the Missouri game. The movement of that overhang during a jumping song was substantial and caused my kids to ask me if it was going to collapse.

Thanks for pointing this out, Magnum Load. It's probably OK, but it would be great to have you follow-up with the proper design folks.
Ag_N_Houston
How long do you want to ignore this user?
AG
OP - did you ever go to a game in the "old" Kyle? You would have really been freaking out on second and third deck back in those days.
Ol Rock
How long do you want to ignore this user?
AG
You should def voice your concern.

I'd rather review this than have something tragic happen.
MagnumLoad
How long do you want to ignore this user?
Old Kyle is all concrete, much more total mass and damping than steel support structure. In the past most of the concern has addressed horizontal movement from swaying people.
Billy Liuccis Facial Hair
How long do you want to ignore this user?
AG
T&P's for the remodeled Kyle
Philip J Fry
How long do you want to ignore this user?
AG
quote:
Old Kyle is all concrete, much more total mass and damping than steel support structure. In the past most of the concern has addressed horizontal movement from swaying people.


The student body recently started adding a hitch to their sway. Like I said, we should already have plenty of data from the old design to properly estimate these kinds of forces.
 
×
subscribe Verify your student status
See Subscription Benefits
Trial only available to users who have never subscribed or participated in a previous trial.