Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Dynamic Shear Modulus vs. Static Shear Modulus

Dynamic Shear Modulus vs. Static Shear Modulus

Dynamic Shear Modulus vs. Static Shear Modulus

I'm being asked to design a footing for a piece of vibrating equipment and the geotechnical report gives no dynamic soil properties. The goetechnical engineer completed their work over 3 years ago, long before my firm was even hired, and there's no way the client will pay for further geotechnical investigation at this stage.

Question #1: The geotechnical report does however give static soil properties. The area is primarily meta-sandstone. I'm looking for a formula that relates the dynamic shear modulus of rock (specifically sandstone) to the static shear modulus. Is there such a thing?

Question #2: The static shear modulus is given in the report as 80 MPa. Does that seem to be in the ballpark?

RE: Dynamic Shear Modulus vs. Static Shear Modulus

DCBII, do you have the results of any geophysical survey in the area? with a Vs (sher wave velosity) value? The 80 MPa value doesn't sound unreasonable, we usually define a Gmax or G0 which means G at small deformations (usually measured by geophysical means), then we should apply a degradation scheme which is different in dynamic and static conditions. So if your G is a G0 there might be no degradation depending on the machine, otherwise a totally approximate way to degrade is to apply a 0.5 factor, which is also applied to static degradation.

Bottom line, does the report specify Gmax or G0 or just G static? To be more precise, a static G should have an 'operational' label which means it has already been degraded

RE: Dynamic Shear Modulus vs. Static Shear Modulus

It calls it an "Estimated Static Elastic Shear Modulus". It does not specify whether or not it's been degraded. I do have a seismicity report, which gives a response spectrum for a shear wave velocity of 1800 m/s, but I don't think that's necessarily the shear wave velocity on site. Typically the response spectrum values are generic and need adjustment using coefficients to suit actual site conditions.

RE: Dynamic Shear Modulus vs. Static Shear Modulus

Hello, i am curious have you fixed the problem ?

RE: Dynamic Shear Modulus vs. Static Shear Modulus

Dear friends, u can use limit analysis for your work. in this method there is no need to use young modulus and shear modulus. u can download basic information from this link: uploadboy.com/aoxq7tmmzq3u.html

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close