Vibrations for Elevated Running Track in Gym
Vibrations for Elevated Running Track in Gym
(OP)
I have not used the AISC Design Guide on Floor Vibrations and I am in the process of getting familiar with them.
I have a pre-engineered metal building being used for a gymnasium and the building vendor will be designing a running track that wiil be suspended from the metal bldg framing. At the outer wall, the track framing will tie into the frame columns on the sides and the wind columns on the ends. The open side of the track will be hung from the frame members and the roof framing.
I need some help providing the vibration design criteria for the engineers at the metal building company. This part of the design was given to them.
I have a pre-engineered metal building being used for a gymnasium and the building vendor will be designing a running track that wiil be suspended from the metal bldg framing. At the outer wall, the track framing will tie into the frame columns on the sides and the wind columns on the ends. The open side of the track will be hung from the frame members and the roof framing.
I need some help providing the vibration design criteria for the engineers at the metal building company. This part of the design was given to them.






RE: Vibrations for Elevated Running Track in Gym
RE: Vibrations for Elevated Running Track in Gym
I just need some experienced guidance developing the criteria. I have the AISC DG 11.
RE: Vibrations for Elevated Running Track in Gym
The natural frequency needs to be high enough so that the step frequency can't match it. The first harmonic of hte walking or running force is VERY large, so you need to ensure that it can't cause resonance. See if the DG provides a step frequency range for running. If it doesn't say anything, I think I'd use 5 Hz.
RE: Vibrations for Elevated Running Track in Gym
In chapter 4 (walking), the peak acceleration is 1.5%g for interior footbridges and the stiffness criteria is 5.7 k/in.
In chapter 5 (rhythmic), the peak acceleration has a range of 4-7%g (use 5%g?) for rhythmic activity only and for aerobics only (light floor), there is a min. natural frequency of 9.2 Hz. Does this make sense?
RE: Vibrations for Elevated Running Track in Gym
Re-read Ch. 5. There's a way to have fn<9.2 Hz.
BTW, if you don't have it, you DEFINITELY need to buy Dr. Tom Murray's FloorVibe to help with floor vibe analysis in general. It's cheap and is extremely helpful.
In your particular case, it would have to be used with caution and I would actually make a FE model if I were doing it--I've done this *exact* thing before and the FE modeling approach worked out well. Build a model of the entire bldg with the track hanging from the RFs.
RE: Vibrations for Elevated Running Track in Gym
The frequency 9.2 Hz came from a table in chapter 5. It is based on typical aerobics values being used in equation 5.1. Actual values may reduce this value.
I won't be doing any FE modeling or any design work at all. I am only setting up the design criteria for the PEMB engineers who will design the track.
RE: Vibrations for Elevated Running Track in Gym
Track, using the footbridge and 5 Hz (unless you can find something else) criterion.
Aerobics room using Ch. 5 criteria, although I don't think you want to say 9 Hz min natural frequency. There's a way in there for calculating the peak acceleration. I'd use that instead. Dig in there and see where their fnmin comes from and I think you'll see why you don't want to use it. Might have to go back to Ch. 2 or 3 (forgot which) to see the background. The only fn limit I'd place on those areas would be one to make sure their step frequency can't match the natural frequency. 5 Hz sounds good to me here also.
RE: Vibrations for Elevated Running Track in Gym
Again, I designed the roof members, and let the PEMB supplier design the frames. I gave the PEMB supplier the reactions at the frames.
DaveAtkins
RE: Vibrations for Elevated Running Track in Gym
RE: Vibrations for Elevated Running Track in Gym
DaveAtkins
RE: Vibrations for Elevated Running Track in Gym
RE: Vibrations for Elevated Running Track in Gym
If I understand your first post, you checked the design for both walking (footbridge) and rhythmic (aerobics) and found that the walking controlled. Our track is 11'-8" wide and the span is about 120'.
Do these specifications make sense?
Rhythmic: The Minimum Required Fundamental Natural Frequency shall be 9.2 Hz. Peak Acceleration from Rhythmic Excitation shall be less than 5%g with a participant load of 4.2 psf.
Walking: Peak Acceleration from Walking Excitation shall be less than 1.5%g with a 92 pound force. The track floor system shall have a minimum floor stiffness of 5.7 kip/inch.
RE: Vibrations for Elevated Running Track in Gym