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[SEAOC] ASCE NO. 58 Use[Subject Prev][Subject Next][Thread Prev][Thread Next]
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- Subject: [SEAOC] ASCE NO. 58 Use
- From: scott.horn(--nospam--at)srs.gov
- Date: Fri, 14 Jun 1996 12:22 -0400 (EDT)
I have encountered this situation when designing a buried structure. I found ASCE 4-86 to be especially useful. But be careful in it's use. It considers a yielding and non-yielding wall. And if you are attempting to save your customer money and there are not other drivers which would dictate thicker walls, your wall will yield. The equation as shown in ASCE 4-86, I believe is in error. The equation for the active solution (the Mononobe-Okabe method) has two "angle of wall friction" summed then evaluates the cosine. This is wrong! The second term should be the "angle of friction of soil" value. Use caution because this equation does not consider surcharge effects and you will be in a dilemma there to decide if you will use the equivalent soil height and increase the wall height or some other evaluation. The other considerable impact is if the wall is loaded under a saturated condition. You may need to consider the effects of a hydraulic head. The most effective means of reducing the amount of concrete in a retaining wall job is to tie the floor diaphragm to the top of the wall and consider a fixed-pinned condition. This presumes that you have a floor or roof. You must be sure to carefully detail the connections in this case and check the diaphragm with the structure loads from the building added. You also need to note on the drawing that the diaphragm shall be in place prior to bakfilling being placed. I understand you dilemma, because my brother is an Architect (with and undergraduate in Civil Engineering, basically enough knowledge to be dangerous) and when I designed the 16' high retaining walls in his personal residence in Salt Lake City he had a fit and the phone call cost me a fortune. Another area to be cautious when preparing the drawings is the method of backfill placement. If vibration compactors are used Fang's "Foundation Engineering Handbook, 2nd edition" says this could be the most severe loads the wall will see. Know how this wall is to be built! Good luck, and use some of the site inspections money you got for the job to take a walk. Scott Horn Bechtel Savannah River Site ...
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