Does prestressing affect the natural frequency of a slab.
Does prestressing affect the natural frequency of a slab.
(OP)
I have been carrying out some research and believe that prestressing a concrete member may help to reduce deflection but it does not affect the dynamic modal properties of the member. The natural frequency (1st dynamic mode) of the structure remains the same. Has anyone any comments?






RE: Does prestressing affect the natural frequency of a slab.
The slab would be looked as an uncracked slab and would, therefore, be somewhat stiffer.
Your transformed moment of inertia would change as well... But, I'd probably ignore this and just base the dynamic properties on the gross un-cracked properties of the slab.
RE: Does prestressing affect the natural frequency of a slab.
RE: Does prestressing affect the natural frequency of a slab.
Did it assume Igross for both cases?
What exactly are you looking at? If it is just for the slab, then you should see a difference. If it's for the structure, as a whole, I'm not so sure. The lateral system would dictate that. The lateral system isn't PT is it?
RE: Does prestressing affect the natural frequency of a slab.
Dik
RE: Does prestressing affect the natural frequency of a slab.
2 What stiffness does your software assign to the RC slabs. Unless you specify otherwise it is probably using Igross!
RE: Does prestressing affect the natural frequency of a slab.
thanks!
RE: Does prestressing affect the natural frequency of a slab.
The reason is that in the linear range there is no additional work done against the extra force, over one cycle. What you put in on the way up you get back on the way down.
Cheers
Greg Locock
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