Vibrations:Reinforced Concrete
Vibrations:Reinforced Concrete
(OP)
Does vibaratory loading alter the strength of concrete and reinforced concrete compared to normal static loading?
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Vibrations:Reinforced Concrete
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RE: Vibrations:Reinforced Concrete
RE: Vibrations:Reinforced Concrete
1)Blast loading
2)Earthquake
3)Machine
4)and as you said, footsteps
RE: Vibrations:Reinforced Concrete
RE: Vibrations:Reinforced Concrete
RE: Vibrations:Reinforced Concrete
But, loading with increased strain rate does affect reinforced concrete strength?
RE: Vibrations:Reinforced Concrete
Supposing in reinforced concrete, we have the vibrations produced due to blat loading.
Now,blast loading produces very high strain rate.And, the strength of concrete and steel bars increase significantly with increased strain rate.Right?
Am i right?
Can anyone point out the effects :
1Earthquake
2)Machine
3) footsteps
on concrete strength.
RE: Vibrations:Reinforced Concrete
For footsteps, resistance to unbalanced rotors, etc., the elastic modulus of concrete is typically taken as 35% higher than the ACI value. This is standard in the AISC DG11 and results in excellent comparisons to vibe test results for simple specimens.
RE: Vibrations:Reinforced Concrete
RE: Vibrations:Reinforced Concrete
However, I have done tests that have shown using Ig is still valid and actually more accurate at predicting vibrations that Icr
RE: Vibrations:Reinforced Concrete
I have a funny example, a 3 equal span lab specimen. It has large cracks over the supports and acts like 3 simple beams for deflection. For vibration, though, its first three natural frequencies are predicted within 2% if it's computed assuming a 3 span continuous beam. The mode shapes are almost exactly like the theoretical ones for a 3-span beam.
Vibe is a lot less like stiffness analysis than it would seem at first. It's a lot more like stability.
For example, nobody believes it at first, but an equal span continuous beam has the same natural frequency as the single span one. As one span flops up, the other flops down. Kinda reminds one of two span column buckling.
RE: Vibrations:Reinforced Concrete
That, with increase in strain rate concrete strength increases as mentioned above.
However, he wanted to understand this intuitevely, that as the strain rate is fast the material is becoming stronger?Can anyone give an intuitive/physical understanding for this?
RE: Vibrations:Reinforced Concrete