×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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

Jobs

Soil Pressure - U.S. to Metric Coversion Question
3

Soil Pressure - U.S. to Metric Coversion Question

Soil Pressure - U.S. to Metric Coversion Question

(OP)
Hello, I hope I have found the right forum.

I have a project that requires addition of metric values to a set of standards now shown in U.S. only (they will now show dual units).

I am not an engineer, but have construction and technical background.

I am somewhat confused as to the proper conversion (standard useage) for the U.S. designation of Pounds Per Squre Foot(PSF)to metric.

Is the normal conversion factor:
 square meter (kg/sq m)
{note I could not show supersubscript 2 to define "squared)

Or would Pascal be appropriate?  (I am not certain if Pascal is a square/unit measurement or just pressure).

If Pascal is a square/unit measurement, would either of the two be appropriate?

I hope I laid this out so it is not confusing.

RE: Soil Pressure - U.S. to Metric Coversion Question

rscott,

Pascal is NOT the right measure for soil pressure, since 1 Pascal is such a low pressure. You can think of it as the weight of 1 'standard' apple (the Newton being the unit of force)on every square metre.

The usual geotechnical pressure unit is kilopascal.  The rate of conversion is 1 kPa = 20.885 lbs/sq.ft.

RE: Soil Pressure - U.S. to Metric Coversion Question

(OP)
Perfect...

Right, kilopascals it is, I should have been clearer on that point.

I just wanted to make sure the conversion factor was acceptable.

i.e 2700 psf = 129.28 KPa.

Thanks so much!!

RE: Soil Pressure - U.S. to Metric Coversion Question

Ingersoll Rand sells a book "Cameron Hydraulic Data" which has the best conversion information I have seen. If you are doing a lot of converting it will prove very useful

RE: Soil Pressure - U.S. to Metric Coversion Question

As originally American, I loved the English system - for you seldom lost decimals.  Moving to Canada and now working overseas, they all love the metric (or SI - system internationale) but, you know, even thought kPa ought to be used for pressure (MPa for concrete and rock strengths), our contract documents are all over the place:

N/mm2 (= kPa)
kg/cm2
ton/cm2

etc.  Then there is the "force" vs the "mass" pressures.  Generally, all these differ by some factor of 10 or 100 but it is crazy to have to always have to remember which.  Insist on kPa; MPa.  For unit weights, use kN/m3, not g/cc or kg/m3.

Best regards

RE: Soil Pressure - U.S. to Metric Coversion Question

Hi, BigH,

N/mm2 is actually MPa.  And for any dynamic calculations, we still have to consider mass as well as weight, so kg/m3 will have to stay in our vocabulary, like it or not.

RE: Soil Pressure - U.S. to Metric Coversion Question

austim:
    See what I mean?  I have MPa written down somewhere - but it is always a pain to have to find my little crib sheets!!  May in dynamic calculations it is easier to use kg/m3 (although, I suppose you could use kN/m3*.981 (or is that /.981??).  But for soil weights for stability calcs, settlements, etc., kN/m3 is best!!
    By the way - the CRC Chemistry handbook has a great listing of really wierd conversions besides common ones!
    Take care - best regards.

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!


Resources