Multistorey basement walls

[ajk1]

Does anyone know where I can get a simple multistorey basement walls program or spreadsheet that will calculate the maximum positive and negative moments for each storey of a multistorey basement retaining wall due to lateral soil pressure on the wall, as well as the design shear force at shear critical sections near top and bottom of each storey of the wall? A few years ago I wrote a neat analysis and design spreadsheet that would do this, but it does not allow for the soil pressure coefficient and density to change due to say rock below the earth part way down the wall. For example, if there is earth for 15 feet below grade, and then it becomes shale with a much lower lateral pressure coefficient and different density, my spreadsheet can't handle that.

 

[BAretired]

Why don't you write a new spreadsheet which does handle that?

BA

 

[a7x1984]

You should never trust somebody else's spreadsheet. The time needed to check and test it is better spent in editing your own.

In Russia building design you!

 

[BAretired]

I agree completely. And furthermore, you know what assumptions were made in your own spreadsheet.

BA

 

[XR250]

Just use a simple 2 DOF beam analysis program - one beam with multiple supports and varied loadings.

 

[briancpotter]

Enercalc's concrete beam module should work fine for this.

There's also a piece of software called BCAN that I've used previously that should work, which can be found here:

https://precastengineer.com/bcan

. BCAN is only $80, which is around as cheap as can be expected, and is a better deal than spending half a day to a day rolling your own solution.

Hope that helps.

Brian C Potter

http://simplesupports.wordpress.com

 

[ajk1]

I take it that so far no one is aware of tried and true software designed specifically for multistorey basement walls. For cases where the pressure coefficient Ko or soil density changes at depth, I generally do it by manually working the loads and inputting it to our own proprietary concrete beam prgramme (similar to the procedure suggested by some of you people), but I was looking for something more efficient. If anyone subsequently reading this knows of such proven software I would be interested in hearing about it...otherwise I either keep doing it the way I have been doing it, or I modify my own spreadsheet to handle the case where the Ko or soil density changes part way down the wall (for cases where the soil density and Ko are constant for the full multistorey basement height, the spreadsheet I wrote works beautifully).

 

[a7x1984]

"tried and true" - That is a very relative term, and you will find nothing specifically for multi-story basement walls as it is a design that can easily be taken care of by the programs mentioned by others above with manual input of loadings.

RISA Foundation is another option as it contains retaining wall design. I don't understand how you can get much more efficient than that. It takes all but 15 minutes to manually apply multiple triangular loads and add however many mid-height supports you want.

How often do you perform these designs that you are so concerned with this extra efficiency?



In Russia building design you!

 

[BAretired]

Good point, a7x1984. This type of calculation is not performed very often and when required, why not devote a little extra time to really understand what is going on even if it means doing the calculation (get ready for this) by hand?

BA

 

[PEinc]

It sounds to me like you need a retaining wall design program that can design sheeting walls that are continuous over multiple supports. Try CivilTech's Shoring Suite. It can handle different soil layers and calculate both active and at-rest soil pressures and surcharges. Or, you can enter your own lateral earth and surcharge pressures. It calculated and plots shears, moments, and reactions.

http://www.PeirceEngineering.com

 

[dik]

I use Yakov's continuous beam spreadsheet.

Dik

 

[manstrom]

I would design it as a continuous beam using enercalc or similar. The axial load from the floors above would not change the result significantly.

 

[ajk1]

Thanks for all the thoughful comments. Much appreciated.

We have to do this type of calculation quite a few times during the year - every time we have more than a single storey basement, which is quite often, given the hospitals, office buildings and condos we do with below grade parking etc. , where the grade etc. changes several times around the 4 sides of the building. For example, a recent building in which we were involved had 5 levels of underground parking.

Most likely my 50 years of experience has slowed me down from the speed at which you young guys can do manual calculations, as it took me several hours to work out one wall section for all the pressures and pressure variations, water table effects, submerged unit weights, and changes in pressure where the soil changes to rock, etc. Then input all the various partial triangular and rectangular loads to a continuous beam programme to determine the moments and shears. Then manually detrmine the rebar for the wall and check that the shear stress is ok. All this my spreasheet can do in a few minutes, but my spreasheet does not cover the change in unit soil weight or other changes in pressure that do not occur at floor lines. I think I will expand my spreadsheet that I wrote a few years ago, so that it can handle the water table and pressure changes that do not occur at floor lines.

I am all in favour of manual calculations and encourage any young engineer starting out with us under my mentorship, to design the various elements of a building by hand first, before letting him/her use our programmes. But if we are to be competitive, at some point we have to make use of technology, and we think that a programme for this would pay for itself fairly quickly. Others may disagree, and I respect that.

Again, thanks for the comments. It is gratifying that so many took the trpouble to respond and provide suggestions,

 

[RareBugTX]

I agree with many here. This sounds like a very particular case worth spending the time writing the code testing it and cross checking results.

 

[ztengguy]

Write your own, and then if its good, you can sell it as software.