Example problem 2_Analysis of combined footings

 

Minimum needed version to run this example:

STAAD Foundation Advanced 2024 (24.00.00.248)

 

Unit System Used: kip-in or kip-ft (Imperial)

 

Problem statement:

In the attached STAAD.pro file there are four concrete columns (M1, M2, M3 & M4) modelled of sections W16x77, each with a height of 10 feet. The c/c distance between column M1, M2 & M3, M4 is 20 ft. Each of the column members carry dead and live loads. In this problem we will create analysis criteria and use the same for the analysis of combined footing.

 

Solution: Step by step process

Step 1: Continue with the model from the previous problem (Example problem 2_combined footing (part 1)).

Step 2: To create analysis criteria, click on Analysis > Create > Foundation.

Figure 1

Step 3: “Create Foundation Analysis Criteria” property page will appear. For this example, we will create two analysis criteria. In the first specify the parameters shown in Figure 2 below.

Figure 2

In the second analysis criteria specify the parameters shown in Figure 3 below.

Figure 3

While creating each analysis criteria click on “Select” button.

Step 4: After clicking on “Select” button in step 3 above “Load Combination” window will get displayed on UI. Select the soil and water conditions as shown in Figure 4 below.

Figure 4

Note for the user: As per the soil and water conditions selected, program will calculate the loads for these load conditions and add the same to the load combinations came from STAAD.Pro superstructure model and it will create additional load combinations for each loading conditions. These load combinations can be seen after performing the analysis.

Step 5: In previous example we learn how to create the concrete grade. Now we will assign the same.

First we will assign concrete grade to pedestals. Select all the pedestal, a property page for pedestal will appear. In this property page assign the concrete grade as shown in Figure 5 below.

Figure 5

Step 6: Now we will assign concrete grade to combined footings. Select both the combined footing, a property page for combined footing will appear. In this property page assign the concrete grade as shown in Figure 6 below.

Figure 6

Step 7: Select CF1, its property page will appear. In the analysis criteria field assign “Rigid” analysis criteria as shown in Figure 7 below.

Figure 7

Step 8: Select CF2, its property page will appear. In the analysis criteria field assign “Flexible” analysis criteria as shown in Figure 8 below.

Figure 8

Step 9: Select both the combined footings go to Analysis > Perform > Selected

Figure 9

Step 10: As mentioned in the Note of step 4 above, to view load combinations go to Project Explorer > Analysis Model > Loads > Load Combinations.

Figure 10

After clicking on “Load Combinations”, an object table will get open with list of all the load combinations which includes load combinations came from STAAD. Pro file and load combination created by STAAD Foundation Advanced.

Figure 11