boussinesq contour chart

I am not a structural engineer, just a water resources engineer trying to pass the exam.

hopefully you structures people can help! I have no idea how to use the boussinesq stress contour chart and I can't figure it out. can anyone provide a reference on how to read these things or any instructions?

I thought I knew, but I get the wrong answer on all the review problems using this chart. I searched online and cannot find a "how to".

the chart has semi-circular pressure bulbs at various intervals (0.1P, 0.2P, 0.3P....) and the axis say 0.5B, 1B, 1.5B, 2B

stuckinjersey said:

I am not a structural engineer, just a water resources engineer trying to pass the exam.
hopefully you structures people can help! I have no idea how to use the boussinesq stress contour chart and I can't figure it out. can anyone provide a reference on how to read these things or any instructions?

I thought I knew, but I get the wrong answer on all the review problems using this chart. I searched online and cannot find a "how to".

the chart has semi-circular pressure bulbs at various intervals (0.1P, 0.2P, 0.3P....) and the axis say 0.5B, 1B, 1.5B, 2B

Click to expand...

are you taking the structural exam? Or the water resources/enviro depth? I don't even know what you are talking about and I've passed the PE exam (I took transpo depth).

stuckinjersey said:

I am not a structural engineer, just a water resources engineer trying to pass the exam.
hopefully you structures people can help! I have no idea how to use the boussinesq stress contour chart and I can't figure it out. can anyone provide a reference on how to read these things or any instructions?

I thought I knew, but I get the wrong answer on all the review problems using this chart. I searched online and cannot find a "how to".

the chart has semi-circular pressure bulbs at various intervals (0.1P, 0.2P, 0.3P....) and the axis say 0.5B, 1B, 1.5B, 2B

Click to expand...

Stuck,

What you are asking is not structural, this is geotech. This table should be found in the CERM.

Edit: Moved to the CE section. Mods, you can toss this one if you want.

Stuck,

Boussinesq Stress Contour Chart is used to find the stress increase at a depth say Y with a given or calculated uniform stress (psf or KN/m^2). If you have CERM 10th edition go to A-72. If the stress area is a square then use the square contour chart. For example the area is 10 feet x 10 feet (lets use the width as B) and has a uniform stress of lets say 2000 psf. If the problem is to find the stress increase at the center and at a depth of 10 feet (Y), divide Y/B and you get 1. In the contour chart means 1B or B. If you follow that line to the left and stop at the center below the square, the stress is a little less than 0.4P curve so lets say 0.38P according to my estimate. P is 2000 psf. So the stree increase is 0.38 x 2000 psf = 760 psf.

If the stress increase is needed lets say at the corner at the same depth (10 feet), look for the intersection at the horizontal line 1B and the vertical line that is directly below the corner of the square contour chart. An imaginary curve of about 0.25P will be used. Again I estimated 0.25P because it is about in the middle of 0.2P curve and the next curve above which is 0.3P. So the stress increase at the corner at the same depth (10 feet) is 0.25 x 2000 psf = 500 psf.

As you notice on the chart, the stress decreases as you go down and go left or right from the center.

I hope you learned something.

djgint said:

Stuck,
Boussinesq Stress Contour Chart is used to find the stress increase at a depth say Y with a given or calculated uniform stress (psf or KN/m^2). If you have CERM 10th edition go to A-72. If the stress area is a square then use the square contour chart. For example the area is 10 feet x 10 feet (lets use the width as B) and has a uniform stress of lets say 2000 psf. If the problem is to find the stress increase at the center and at a depth of 10 feet (Y), divide Y/B and you get 1. In the contour chart means 1B or B. If you follow that line to the left and stop at the center below the square, the stress is a little less than 0.4P curve so lets say 0.38P according to my estimate. P is 2000 psf. So the stree increase is 0.38 x 2000 psf = 760 psf.

If the stress increase is needed lets say at the corner at the same depth (10 feet), look for the intersection at the horizontal line 1B and the vertical line that is directly below the corner of the square contour chart. An imaginary curve of about 0.25P will be used. Again I estimated 0.25P because it is about in the middle of 0.2P curve and the next curve above which is 0.3P. So the stress increase at the corner at the same depth (10 feet) is 0.25 x 2000 psf = 500 psf.

As you notice on the chart, the stress decreases as you go down and go left or right from the center.

I hope you learned something.

Click to expand...

THanks . I also had same question as originator of this thread.

Which part of the Boussinesq stress chart to refer if problem asks for stress increase in rectangular footing? The left part of the chart is for continuous and right is for square. Any Suggestions??

If you have any other shape, can be a rectangle, a circle, an L-shaped building, or even a set of multiple buildings, you can use the influence chart on CERM 40-3 (11th ed).

I had to idea how to use these charts either when I stated prepping for this exam (I am Construction PM myself) but I found a great resource. They are videos put together by Texas A&M (a long time ago, so be patient) but they were great , and free to view or download:

/>http://engineeringregistration.tamu.edu/tapedreviews/PEreview.htm

Click on Soils (it is 3.5hrs of video total, but the stress at a depth section is only a few minutes long)

Click on Part 2

And go to minute 1:09:00

The PDFs are available to download also if you want to print them to follow along.

The whole set of available info is here:
/>http://engineeringregistration.tamu.edu/tapedreviews/index.htm

Good luck!

Thanks a bunch!

That is great!!!. I lost too many hairs on that type problem.

Now I hope I get one. Pretty easy.

Is this an AM Question on the new test plan?

talal033 said:

Is this an AM Question on the new test plan?

Click to expand...

You could see this on the AM ...