Foundation Settlement Analysis in STAAD Pro

Footing Type support under foundation support in STAAD Pro V8i:

Almost all the times the STAAD Pro users preferably use fixed or pinned type of supports for frame analysis. However, there are times when the soil below the foundation is elastic & the joint displacements due to settlement in soil have to be taken into consideration in analysis, at such times one can use the foundation support feature provided in the Supports page of STAAD Pro.

Here below I am going to brief about creation of footing type support for a column;

• First create a column member of height 3.5 m & cross-section 0.30 m x 0.30 m.
• In the next step go to General page>>Load & Definition subpage & create a primary load case. In the created primary load case define a nodal load of Fy = -50 Kn & assign it on the top node of the column.

Figure-1

• Now, go to General page>> Supports sub-page & from data sheet area click on create button in Supports-Whole Structure window.

Figure-2

• By doing so the Create Support window will be prompted on screen, now choose foundation tab from above.
• Under the foundation tab three options viz. footing support, elastic mat & plastic mat are available. In this post we will discuss about how to model a footing type of support using Length (L) & Width (W) values.

Figure-3

• Define the values for ‘L’ & ‘W’ as 1.5 m, choose Y direction for spring generation & define the value of subgrade modulus as 2000 kn/m2/m (for SBC of 100 Kn/m2 & 50 mm allowable settlement) & click ADD. After adding the support to Supports-Whole Structure window, assign the support to the bottom node of the column.
• Now, in this example we have modeled a column of 3.5 m high 0.30 m x 0.30 m section size supported on 1.5 m x 1.5 m size footing loaded with an axial load of 50 kn.

Figure-4

• Finally go to Analysis & Print Page & assign No Print command to the structure, afterwards give Run Analysis (Ctrl+F5) command from Analyze menu.

Figure-5

• Once the analysis is complete, close the STAAD Analysis engine window & go to Post Processing mode from the Mode bar.

Figure-6

• In the Post-Processing Mode go to Node Page>>Displacement Subpage>>Node Displacements Table (on the right side of the screen). Here in the Node Displacements table check for the displacement of support node in Y direction, the value provided generated here is in mm & this displacement value is calculated on the basis of Area of Footing (L x W), Soil Subgrade Modulus, Spring Constant ‘K’& Load on Column.

Figure-7

Figure-8

• Kindly, refer the attached image for the manual calculation of support displacement for verification & for any query or suggestion kindly post your comment in the comment box.