I've designed a 14' x 14' x 3' mat foundation to support a jaw crusher & steel support frame, but now I'd like to check the natural frequency in comparison to the operating frequency of the machine (3.8 Hz). I will be using a finite-element model in Staadpro that utilizes spring supports at each node of the foundation.
My main question is whether or not my calculated values for the spring constant are reasonable.
Right, wrong, or otherwise, I cannot convince the customer or my employer (a design/build construction company) to pursue geotechnical services to establish better soil parameters. So, for the sake of furthering the conversation, let's assume the following:
soil poisson ratio = 0.35
void ratio = 0.4
I've been using ACI 351.3R-04 as my main reference. For this application, I was assuming a uniform soil condition and using the Richart-Whitman model as shown in section 4.2.1.1. Since this is a square foundation, the impedance can be found from equations (4-13e) thru (4-13g).
The dynamic shear modulus has been calculated as 1,206,105 psf (per equation 3-34), assuming a probable confined pressure of 300 psf.
Vertical impedance, kv = 54,553 k/ft
Horizontal impedance, ku = 43,311 k/ft
These spring values above just seem high to me. Are they within reason?
*NOTE - I will post this in the foundation design section as well......thanks
My main question is whether or not my calculated values for the spring constant are reasonable.
Right, wrong, or otherwise, I cannot convince the customer or my employer (a design/build construction company) to pursue geotechnical services to establish better soil parameters. So, for the sake of furthering the conversation, let's assume the following:
soil poisson ratio = 0.35
void ratio = 0.4
I've been using ACI 351.3R-04 as my main reference. For this application, I was assuming a uniform soil condition and using the Richart-Whitman model as shown in section 4.2.1.1. Since this is a square foundation, the impedance can be found from equations (4-13e) thru (4-13g).
The dynamic shear modulus has been calculated as 1,206,105 psf (per equation 3-34), assuming a probable confined pressure of 300 psf.
Vertical impedance, kv = 54,553 k/ft
Horizontal impedance, ku = 43,311 k/ft
These spring values above just seem high to me. Are they within reason?
*NOTE - I will post this in the foundation design section as well......thanks