BEAM ON ELASTIC FOUNDATION ANALYSIS
BEAM ON ELASTIC FOUNDATION ANALYSIS
(OP)
Hi, I have a question. I need to know if it is well done to apply the wrinkler model and use the Hetenyi formulas to calculate the structurals parameters such as: moment flexural, shear forces and deflexion, just in the same way established in the BOWLES, FOUNDATION ANALYSIS & DESIGN because I need to analyse an underground beam structure that it is used for installed underground electrical cables lines. I supposed you know what I mean, it is a beam of a base not so big probably we are talking about 40 in. a square size but the beam of this type are very long more than 10 ft. For the soil parameter I used the subgrade modulus of reaction K, from any table book. Because I think that the most critical soil to analyse underground structure is the clay soil type, then I used the average from any table values I reached. Also I need to know if I am Ok. in using this concepts to make an approachement analysis using the beam on elastic foundation for the above mentioned structure type?





RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
Your post does not have enough information for a reasonable answer. We need a lot more information tin order to help you.
By the way, a 1 meter by 3 meter footing is not very big; why are you trying to perform a detailed analysis on such a small foundation element?
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
So maybe and in this case the elastic foundation method can bring me more realistic results because it will be an underground structure design.
Well, another thing is the soil type. In the construction area here in my country the most is the clay type soil. But also I know it will be another kind of soil type. In all case ¿what value of subgrade modulus of reaction, K, it will be the correct selection in general? And, How can I get the more realistic value for the type common soil, for example the clay soil type or sandy clayey soil, etc? Cause you told me that I can't simply look for it in any table.
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
Please can U tell me, If this Ok?
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
If you are putting a lot of cables through the PVC and are concerned about settlement, then the use of k won't do you much good. You need the help of a local geotechnical engineer.
If you are concerned about the effects of heat on the surrounding soil, then you need a local geotechnical engineer.
The modulus of subgrade reaction will not really help you - unless you want a false sense of security.
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
With the hetenyi formula I can find the numerical value of the flexural bending moment of the beam just in fact to calculate numerically the amount of steel quantity that the beam requires. So that's why I ask you if its Ok that the numerical value of K can get it from the Bowles book.
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
It is better to have the modulus of subgrade vertical reaction, k, obtained by test on the actual site, but this is not always practical. I have used values of k from obtained from books many times. In those cases, I have checked the foundation for the two extreme values of the range given, to have a feeling of how the moments, soil pressures and deflections would vary. Also, I would verify that the actual soil fits the soil description of the reference.
I have used Hetenyi's formulas, and they require a lot of calculations. A spreadsheet or simple computer program would be useful.
Remember that uniform load along the beam do not produce moments (unless k varies.) Only concentrated loads and varying distributed loads will do.
Regards
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
Well, I tried an evaluation using the spreadsheet, applying: the "K" value from the National Structural Code table, distributed load (dead, live and seismic) applying the Hetenyi's formula, and from that, I obtained certainly, lower moment values. Perhaps, this mean that the beam structures shall be need the minimal amount reinforcement according to the ACI 318M-99. In fact, I have this ACI edition.
But if you have any other suggestion, you can tell me. So it will help me to view and do my work much better.
*****Have a Happy New Year 2003********
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS
Every job I've worked on that had these, refered to them as duct banks even though they were carrying electrical conduit.
I might be missing something but...
Unless the site experiences a significant differential settlement under the duct banks, you should be able to use minimum reinf. I think the most important item is to ensure adeqate soil compaction over the duct banks especially if they are on top of each other. The weight of the concrete is about equal to the weight of the soil, so as long as your first duct bank bears on virgin soil, and the finished grade elevation is equivalent to initial grade elevation, you have not increased the soil stresses any appreciable amount.
However, if there is the potential for equipment or vehicular traffic over the banks, now or in the future, you may need to re-evaluate.
RE: BEAM ON ELASTIC FOUNDATION ANALYSIS