Footings are the most important part of a structure. The complete load of the structure is transferred to the soil with the help of the foundation itself. Earlier, I created the spreadsheet for square footing design. It had limited utility that’s why I have created this rectangular footing design spreadsheet.
However, this spreadsheet is part of something big I am working on. This is the part of something big which I am working on and might take a while to come up? Anyways, this spreadsheet can be used for designing a rectangular footing, actually two footing simultaneously it can be useful for the purpose of comparison and learning. Off course, as usual, I have tried to make it in such a way that it can be used by the learner, designers, students and also teachers. keeping everything open and simple. Nothing which I haven’t used or explained in my previous spreadsheets have been done in this one.
Working of Rectangular Footing Design Spreadsheet
This spreadsheet is basically comprised of five sections as mentioned below one by one in details.
Input Section Rectangular Footing Design Spreadsheet
This is the portion where most of the inputs are to be entered. “Most of the inputs” as there are some choices that can be entered at a later stage. Cells for entering the data is shown with a filled background. At the position where there is some advised value but a user may want to change the value for example. “Factor of safety” a default value is entered and an input place is provided after “or” where required value can be entered and value that will be used further is shown after “use”.
Representation Section of Rectangular Footing Design Spreadsheet
The 2nd section of the spreadsheet is representation where a diagram of the footing is shown and various dimension are also entered. It is shown in the image below.
Depth of Footing Section of Rectangular Footing Design Spreadsheet
This portion shows the calculations involved in finding the depth of footing. It is founded using Bending moment consideration as well as Punching shear consideration as shown in the image below. However usually value calculated due to punching shear consideration is smaller. Depth value calculated along all the direction is considered and the maximum value of depth is used.
After calculating depth an option to manually enter the depth is also given which can come handy when the is a failure which can be eliminated by increasing or decreasing the depth of the footing. Depth of the footing at the edge is kept one-third the depth of footing at the face of the column which can also be altered manually in the cell with filled background.
In this section amount of steel reinforcement along both the direction is calculated as shown below.
Check Section of Rectangular Footing Design Spreadsheet
In a foundation, it is very important to check the safety against shear forces at both the critical section. In this spreadsheet, conditional formatting is used to highlight if there is a failure in shear as shown below.
Version 1_0 of Rectangular footing design spreadsheet
Click Here for the Protected version 1_0 of the spreadsheet.
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