Rigidity of pile mat
Rigidity of pile mat
(OP)
Hi i have a pile mat supported by six piles below the mat.
The loads on the pile mat are almost negligible, however i want to design the reinforcement on the pile mat due to self weight and overburden soil.
Considering a 1 meter width strip spanning between the piles, (self weight of pile mat and overburden soil on the strip)
If the slab is not rigid different procedure has to be adopted to calculate the moment on pile cap.
Kindly correct me if i am wrong also let me know how to find the rigidity of the pile mat. How to check one way shear in the pile mat?
Link
The loads on the pile mat are almost negligible, however i want to design the reinforcement on the pile mat due to self weight and overburden soil.
Considering a 1 meter width strip spanning between the piles, (self weight of pile mat and overburden soil on the strip)
If the slab is not rigid different procedure has to be adopted to calculate the moment on pile cap.
Kindly correct me if i am wrong also let me know how to find the rigidity of the pile mat. How to check one way shear in the pile mat?
Link






RE: Rigidity of pile mat
RE: Rigidity of pile mat
For the mat, you could make a simple assumption fixed - fixed beam with an end displacement of 1 unit. Moment = 6*EI/L^2, Shear = 12*I/L^3/ That will at least get you in the ball park for your comparison to the pile stiffness.
RE: Rigidity of pile mat
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Rigidity of pile mat
Comparing predicted pile settlement under load with estimated mat deflection at that pile location will give an idea if rigidity is reasonable. The goal is to have:
Mat Deflection at a Specific Pile Location << Than Specific Pile Settlement at Design Load
The most direct way to minimize deflection is to make the mat "thick" (increase the moment of inertia) compared to its horizontal dimensions. Consider it analogous to the Span / Depth radio of a structural beam.
From your sketch:
Maximum mat horizontal dimension = 5.5 meters
Mat thickness (ignoring the 0.075 meters that the piles are embedded in the mat) = 0.65 meters
"Span" / Depth Ratio = 5.5 m / 0.65 m = 8.5
Based on my experience, and for reasonable loads, a ratio of 10, or less, will be quite rigid. A ratio over, say 12, becomes suspect.
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Rigidity of pile mat