Minimum needed version to run this example:
STAAD Foundation Advanced 2025 (25.00.00)
Unit System Used: Kip-in or Kip-ft (Imperial)
Problem statement:
In the attached STAAD.pro file there are two column members modelled of sections W36x853, each with a height of 10 feet. Each of the column members carry a dead vertical downward load of 90 kips and a dead moment of 62 kip about the global X axis. Model foundations of 100 in x 100 in under both the columns along with the material and soil data using STAAD Foundation Advanced. Import the STAAD.Pro file into the application.
STAAD file: STAAD File for Example 3
SFA file: Example_3 Part-1
Considerations:
The steel columns are supported on the top of two pile cap foundations through pedestals and the pile caps are founded at 4 feet below the top of the soil level.
Material Data:
Characteristic compressive strength of concrete: 4000 psi
Strength of reinforcing steel: 60 ksi
Soil Data:
For overburden loads, assume medium dense sand dry density as 90 lb/ft3 and wet density of the soil as 100 lb/ft3.
Assume pile dia of 24” ; Embedment Length = 3”; Compression Capacity = 100 kip, Tension capacity = 30 kip , Shear Capacity = 30 kip; minimum c/c distance of piles = 60” ; minimum edge distance = 8”
Water Table Data:
2 ft. below ground level.
Load Data (as defined in STAAD.Pro file)
LOAD 1 LOADTYPE Dead TITLE DEAD LOAD
JOINT LOAD
2 4 FY -90 MX -62
LOAD 2 LOADTYPE Live REDUCIBLE TITLE LIVE LOAD
JOINT LOAD
2 4 FY -23
LOAD COMB 3 1.2 DL + 1.4 LL
1 1.2 2 1.4
LOAD COMB 4 1.0 DL + 1.0 LL
1 1.0 2 1.0
Solution: Step by step process
Step 1: Make sure that the STAAD.Pro file is not open. SFA will not be able to import a STAAD.Pro file which is already open.
Step 2: Open the STAAD Foundation application and click on “Import STAAD.Pro File”. Please refer to Figure-1 below.
Figure - 1
Step 3: In the form that appears, please browse to the STAAD.Pro file in your computer by clicking the “Browse” button. As defined in the problem statement, the soil level is defined as 0 ft. We consider the datum at the same level as the top of the soil surface and hence, we specify it as 0 ft. as well. The water table is considered as 2 ft. below the ground level, and hence we specify it as -2. Now, press the “Create” button.
The following figure (Figure-2) shows the sequence of the steps to be followed.
Figure - 2
Step 4: The STAAD.Pro file is unanalyzed. Unless it is analyzed, SFA will not be able to find the reaction information which will be created as loads on the foundation. Hence, the application asks the user if he would like to run the STAAD.Pro analysis. Say “Yes”. Please refer to Figure-4 below.
Figure – 4
(If you have already analyzed the STAAD. Pro file, then pop-up message, shown above would not appear)
Step 5: Now the “Model Import” box appears. Press, the “Import” button, as shown in Figure-5.a below.
Figure-5.a
Note - The above-mentioned pop-up page also helps to control the definition of service and ultimate load combinations. If the STAAD. Pro models already contain combinations, they are imported into SFA as service or ultimate combination as identified by SFA. You can either accept the suggestion or change the combination type before importing as per your decision. Fig 5.b shows the option to view the load cases and view , investigate/ include or exclude and edit combination types.
Figure-5.b
Step 6: You will now see the physical forms of the columns that you have defined in the STAAD. Pro files now appear on the SFA viewing area. Please refer to Figure-6.
Figure-6
Step 7: Now, create the first pile cap foundation under the left column. Click on Geometry > Pile cap > Point. This is a way of creating the pile cap foundation using the point method. Please refer to Figure-7 below.
Figure-7
Step 8: A pop up page for defining concrete grades would appear. Please specify the concrete grade as per your need. You can specify design code, and concrete grade here and click “Add Concrete Grade” to include this grade for this model.
Figure-8
Step 9: Another pop-up page for defining pile types appears. Please specify pile diameter, capacities of pile, embedment length etc. and click “Create Pinned Pile Support” to include.
Figure-9
Note- Concrete Type and Pile specification pop up pages come only for the first time if they are not defined before creating a pile cap. Once they are already available, they can be used /assigned. Concrete type, pile specification can be freshly created form the interface and that would be explained later.
Step 10: The “Create Pile Cap” box appears. Please specify the modelling parameters as shown in Figure-10.
Figure-10
Note for the user: “Column Alignment” is set as “Top”, as it is assumed that the column transfers its load on the top of pedestal. We said “Yes” for pedestals below steel columns, which means that if there is a gap between the bottom of the column and the top of the foundation slab, that would be filled by the pedestals. SFA would calculate a default size of the pedestal (for concrete column, pedestal size as the same size of the column and for steel column, considering a projection for base plate) and assign. Later, if user wants to change the pedestal size, a new pedestal section can be defined and assigned for the respective pedestal. The plan coordinates of the center of the foundation is X=0 ft and Z = 0 ft. Since, the foundation is bottom fixed the Y is – 4 ft, which the level where the pile cap is founded.
You can change the pile arrangement from the button beside “Pile Configuration”. A new page would pop up where you can select from a range of arrangements. Please refer Fig 10.a as below.
Figure-10.a
Press the “Create” button.
Step 11: Now, our first pile cap under the left column has been modelled. You will see that a representative base model has been created under the steel column and the remaining gap between bottom surface of the base plate and top surface of the foundation slab has been filled with pedestal.
Figure 11
You will also notice a bluish representation on the top of the foundation slab. This is representative of the water present in the soil up to the level of water specified, which is 2 ft. below the ground surface.
Step 12: Now, we want to create the pile cap foundation under the second column, which is on the right. However, we will use a different method in creating this foundation. So, the user clicks on Geometry > pile cap > Object. This is to create the foundation by clicking on the object or column under which it is to be created.
Figure 12
Step 13: The “Create Pile cap” box pops up. The user needs to take his mouse over the column in the viewing area and click on it. The user will see that the member number is now registered as “Selected Object” – please refer to the highlighted information in the “Create Pile cap” dialog box. Press the “Create” button.
The foundation is now shown for both the columns (Figure 13).
Figure 13
Step 14: Now, we will go for the material creation of concrete and rebar steel, as is specified in the problem statement. Go to Specification > Concrete > Select, as shown in Figure 14.
Figure 14
Step 15: The following box pops up on the screen. Select the check box besides 4000 psi to specify the concrete strength. Now, click on “Add to Model”.
Figure 15
Note- Steps 14 & 15 are demonstration purpose only, as we have already created concrete grade through pop up page while creating the first pile cap. Follow step 14 & 15 for adding a new grade of concrete.
Step 16: Now, select reinforcing steel grade by going to Specification > Rebar Steel > Select.
Figure 16
Step 17: In the box that pops up, select appropriate steel grade and select “Add to Model”.
Figure 17
Step 18: Now, let us finally specify the soil properties as has been instructed in the problem statement. Let us click on Specification > Create (Soil).
Figure 18
Step 19: In the “Create Soil” box, specify the following parameters. Once done, please press the “Create” button.
Figure 19
Step 20: Finally, click on Loading > Assign Soil Overburden for assignment of topsoil. Refer to Figure 20.
Figure 20
Step 21: Now, follow the steps as shown in Fig 21 to assign the soil overburden.
Figure 21
Step 22: Once, you have clicked on the “Assign” button, two brownish layers appear beneath bottom and above the foundations to show that the soil support and soil overburden have been assigned to both the footings. Please refer to Figure 22.
Figure 22
Step 23: Click on Support > Create> Pinned for opening the page for pile type creation. Refer to Figure 23.
Figure 23
Step 24: A page “Create Pinned Pile Support” would appear. Input Pile name, pile diameter, embedment depth, and capacities. Click “Create” to generate a new pile type.
Figure 24
Note1- As, already a pile type is available, these two steps (23 & 24) are optional, use this step if you need to create multiple pile types and assign them.
Note2- In the same manner, you can create a spring pile also. For rigid method, all piles would be considered as pinned pile, and for flexible (FEM) method, piles can be either pinned or spring pile.
Step 25: Select the pile cap and a page “Properties- Pile cap” would appear. You can change the assignment of pile type from a available list, assign concrete grade, redefine soil and water level, change arrangement type etc.
Figure 25
Step 26: Click on Specification > Manage Profile. A page “Manage Profile” would pop up. You can input Section type and dimensions and click on “Create” to generate a new section profile for pedestal.
Figure 26
Note- This step is optional as we are not going to change the default pedestal section.
Step 27: Select pedestal/ pedestals. “Properties- Pedestal” page would appear. From this page, you can assign the concrete grade to pedestals and also can change the section profile of the pedestal.
Figure 27
Concluding Remarks: Now, this pile cap has been modelled along with it’s associated material properties, pile type, soil overburden, pedestal etc. Now, this model is ready to be set for analysis and post-analysis.