RECTANGULAR SPREAD FOOTING ANALYSIS

It is a simple iterative solution that a friend and myself developed many years ago for the HP41CX programmable calculators based on an article and procedure written by Eli Czerniak. It might be best if you merely "borrow" the procedure in my spreadsheet and embed it into your own. I do not mind. It's involved and a bit convoluted to explain in words. However, the main thing is that it works.
If you want to [email me](/404/), I'll be glad to send you a PDF copy of that Czerniak article.
Alex

Jirair,
I'm not sure why you are having issues with using my FOOTINGS.xls spreadsheet workbook. I make use of input data validation comments as well as other general comments (denoted by red triangles) to hopefully clarify the user input or explain any restrictions or limitations in the input.
All of the spreadsheets that I write make use of comments to varying degrees, and I've never had any complaints from anyone else before about them.
The worksheets are protected, but not with a password. However, unprotecting them will not make the comments go away, but you can blow them away in your own personal copies if you choose.
That's about all I can offer you on this subject.
Regards,
Alex

I have added a new worksheet to the "FOOTINGS.xls" spreadsheet workbook. This new worksheet deals with octagonally shaped rigid spread footings, and will perform the bearing pressure analysis, as well as stability checks for both overturning and sliding. With octagonally shaped spread footings being commonly used for the support of round vertical tanks, vessels, and stacks, I felt that this was a worthwhile addition to the workbook. The required coefficients used in the analysis are automatically extracted and interpolated from the Process Industry Practices (PIP) Document STE03350, "Vertical Vessel Foundation Design Guide" (2007).
Also, in the "Unsymmetrical Footing Base" worksheet, I added/expanded the comment boxes pertaining to the original general stress equation used to better clarify the equation's use and how the sign convention used in the worksheet relates to the original equation.
Finally, in all of the worksheets where a plan view plot of the footing is created, I revised the procedure for obtaining/maintaining a more correct aspect ratio for the plot. Off of the calculation page and to the upper right, the user now inputs a value which is termed as "Axes Lengths Ratio"......the ratio of the actual on-screen measured lengths of the X and Y axes. This should keep the plots looking more to correct scale than they have in many cases in the past.
The current version of this workbook is now version 3.7.

In the "Footings (Table)" worksheet of the "FOOTINGS.xls", it was discovered that original intended criteria for use of top reinforcing was not being handled for all cases. I had originally set the criteria for the use of top reinforcing in the footing base to be for either the case with uplift load on the footing pier and/or for the case when there is no soil cover (D = 0) over the top of the footing. The worksheet was providing top reinforcing when an uplift load was input. However, for the special case of no uplift load along with no soil cover, the worksheet was showing the top reinforcing = 0, when there should have been a calculated value > 0.
I have made the necessary corrections.
This workbook is now version 3.6.

While in and using the "FOOTINGS.xls" workbook recently, I discovered that there were several comment boxes that at some point have gotten shrunk down to where all of the text was not visible. I went through the entire workbook and made the adjustments to the sizes of the comment boxes where required.
While I was at it, I decided to update both the "Footings (Table)" and "Footings (Pier Table)" worksheets to be applicable for ACI 318 Codes, now up through the ACI 318-11 Code version. As best that I could tell, there have been no real changes to the ACI 318 Code (methodology, phi factors, etc.) , at least as far as flexure, shear, compression, and bearing are concerned, since the 2002 version. So it was a relatively easy modification to get those two worksheets updated.
This workbook is now version 3.5.

Here's an update to the "FOOTINGS.xls" workbook which now includes 2 new worksheets, one for a rigid footing analysis with up to 16 piers/load points, and the other to analyze a rigid, unsymmetrical footing base. The names of the 2 new worksheet tabs are "Footing (16 net pier loads)" and "Unsymmetrical Footing Base".
The "Footing (16 net pier loads)" worksheet should help particularly with bearing pressure and stability analysis for equipment foundations involving several piers/pedestals and short walls all on a common rigid foundation. The "Unsymmetrical Footing Base" worksheet should help with analysis of maximum soil pressure for situations where a non-rectangular shaped rigid footing base has to be used.
The current version is now 3.4.

In the "Footings (Pier Table)" worksheet of the "FOOTINGS.xls" spreadsheet workbook (version 3.2), I ran across another "#REF" error (illegal cell reference). This was in the program logic in Column CV28. This error ONLY showed up for a design eccentricity, ey =Mux*12/Pu, which fell between Points #9 (pure moment) and #10 (pure axial tension) on the interaction curve. Like the previous update, this error was inadvertently created during the editing process in adding the calculations for determining the "phi factor" for flexural tension originating in version 3.1. I thought I had caught and covered all of this in the previous version 3.2 update, but unfortunately I missed this one.
I have corrected this, and the updated workbook is now version 3.3.

In the "Footings (Pier Table)" worksheet of the "FOOTINGS.xls" spreadsheet workbook, a "#REF" error (illegal cell reference) was discovered in the program logic in Column CT28. This error only showed up for a design eccentricity, ey =Mux*12/Pu, which fell between Points #8 and #9 on the interaction curve. This error was not in version 3.0 of this workbook, and I must have inadvertently created as part of the editing process in adding the calculations for determining the "phi factor" for flexural tension in version 3.1.
I have corrected this, and the updated workbook is now version 3.2.
While I was at it, I made the following couple of additional changes which hopefully are useful improvements:
In the first 2 worksheets which analyze a single footing at a time, a summary of results was added just off of the main calculation page to the right. This allows the user to quickly check the results during the process of iterating the footing dimensions, etc. in the input data, without having to take the time to either scroll down or "split-screen" the display to view the results.
I grouped all of the separate drawing components which composed the individual sketches in the worksheets into individual grouped drawing objects. This will allow the user to unprotect the worksheet, select the drawing object as a whole, and re-position it in the worksheet to make room for any additional text comments/verbiage if desired.

Along the same lines as the changes I made to the "RECTBEAM (318-05).xls" workbook, changes were made in the 2 table-type worksheets for actual footing design pertaining to the capacity reduction factor, "phi", for flexural tension.
In the "Footings (Table)" worksheet, the program still assumes "phi" = 0.90 for the sake of being able to calculate and suggest numbers of reinforcing bars and size of bars. I've added caution notes in the calculations as well as the "DOC" worksheet to alert the user. Most often in the design of footings the cross section will be "tension controlled", and thus the flexural tension "phi" factor will be = 0.90 anyway. This worksheet now calculates the strain in the tension reinforcing and then calculates the "phi" factor. The user can then review the results for the calculated "phi" factor to determine if it is in fact = 0.90 so that the determined reinforcing can be used. If the calculated "phi" factor is < 0.90, then the user will have to increase the footing thickness until the calculated value of "phi" = 0.90.
In the "Footings (Pier Table)" worksheet for the point on the interaction curve for pure moment (no axial load), the program now calculates the strain in the tension reinforcing, then calculates the "phi" factor, and finally calculates the ultimate moment capacity, (phi)Mn.

This morning while using the "FOOTINGS.xls" workbook, one of the guys thought that he had discovered a problem/glitch because he was getting several #VALUE! errors in results cells when running a footing for a particular loading combination. He was copying a tab to create new tabs for additional loading combinations. Turns out, in editing the loads he had inadvertently used the "Space Bar" to clear or "zero-out" particular values of loadings. Problem is the program is expecting a number or a cleared/blank cell and is not expecting a "space", so it bombs.....giving a #VALUE! error message. When we cleared the contents of the cells, the problem went away, and the worksheet functioned as expected.
I have a message in many, but not all, of my spreadsheets about clearing the contents of input cells not used, and NOT to use the Space Bar to do this. This is just a reminder to you all that just to be safe, always highlight the cells to be cleared, Right-Click the mouse, and then select "Clear Contents". Of course, in most of the programs where a numerical value is expected, inputting values of 0 will also work, but usually that takes more effort and often looks too busy.

This workbook has some concrete design in them, based on the ACI 318-99 Code in their original form. To reflect the use of the ACI 318-05, I decided to give the user the option of selecting what ACI Code is desired to be used, 318-99, 318-02, or 318-05, in those specific worksheets. Once the user selects the desired ACI Code, the appropriate "phi" factors are displayed and used. One word of caution, be careful not to mix & match "phi" factors and load factors from the various concrete codes. It's obviously up to the user to be consistent. For the purpose of just what specific concrete analysis and design is done in this workbook, the selection of either ACI 318-02 or 318-05 gives the same results.