Minimum needed version to run this example:
STAAD Foundation Advanced 2024 (24.00.00)
Unit System Used: Kip-in or Kip-ft (Imperial)
Problem statement:
Further to Part-2, Post analysis check and sizing check are created in this part. Procedure to create Design Envelope that includes design, and detailing setting is covered. Material properties, Analysis criteria, Post analysis criteria, Sizing criteria and design envelope are assigned to isolated footing
STAAD File: STAAD File for Example 1
SFA File: Example_1 Part-3
Solution: Step by step process
Step-1: Create Criteria for Post analysis check
Users can click on “Post Analysis Checks & Design” tab available on ribbon to create a criterion for post analysis checks (PAC). This check includes sliding, overturning and Base pressure checks. Various inputs related to these checks are available . Refer to snap below showing the steps to create criteria for post analysis checks.
Figure 1
For creating Post Analysis criteria, please make sure that the correct analysis criteria are selected. i.e. in this example analysis criteria AC1 should be assigned to IF3 and AC2 should be assigned to IF6 isolated footing. AC1 is the analysis criteria for Rigid footing and AC3 is created for finite element analysis.
Figure 2
Users can include Service load cases (SLS) and Ultimate load combinations (ULS) for Post analysis checks. Refer to snap below to include ULS for Post analysis checks.
Figure 3
Figure 4
Sliding and overturning checks can be selected as per design requirement. Users can include passive soil pressure for sliding and overturning checks. Facility is available to change the Factor of safety (F.O.S) for sliding and overturning checks. % area for loss of contact can be defined. % increase in allowable soil pressure for Eq and WL load combinations can be defined here.
Step-2: Create Sizing Criteria
The purpose of defining sizing criteria is to set the maximum or fixed size of the Isolated footing. refer to snap below to create a Sizing criterion.
Figure 5
The following options are available to define sizing criteria:
- Calculate
- Specify
Calculate Size:
Figure 6
With this option, the program starts with the initial size defined by user while creating footing geometry and does the size iterations till all the post analysis checks are satisfied. Various inputs like Size increment and dimension round off are available to users. Users can click on Convergence Graph to check the FOS available at every size iteration for all checks.
Specify Size:
Figure 7
With this option, users can define the desire size of the footing to perform the post analysis checks. As it is user defined size, the program would check the Post analysis checks for defined footing size.
Step-3: Create Design Envelope
This includes the assignment of design and detailing settings for cross section design of isolated footing and performing design.
Refer to snap below to create design criteria.
Figure 8
Figure 9
Element type should be Isolated footing. Option is provided to select the design code to create design criteria. Based on the design code selection various design settings would be available to design isolated footing. refer to snap below showing various design setting inputs.
Figure 10
Users can set values related to clear cover, minimum percentage reinforcement etc. Facility is available to select/unselect punching, one-way shear, flexural crack-width and thermal crack-width checks based on project requirements. Side face reinforcement can be provided as per user’s requirements. Settings related to preferred spacing, and legs of shear reinforcement are available.
Figure 11
Concrete grade and reinforcement grade can be defined in design criteria. Program allows to select list of diameters to be used for design and detailing. Design code wise rebar list is available. Separate list is available for flexural (main) and shear (secondary) reinforcement.
Next step is to create detailing criteria for isolated footing. refer to snap below,
Figure 12
Reinforcement detailing related settings are available under detailing criteria.
Figure 13
Create Design Envelope:
Figure 14
Design envelope includes the selection of Element type, analysis, design and detailing criteria. While creating design envelope, please make sure that the correct Analysis criteria is selected. In this example, the isolated footing IF3 is assigned with design envelope DE1 which includes AC1 Analysis criteria. IF6 should be assigned to design envelope DE2 which includes AC3 Analysis criteria.
Assignment of all settings to Isolated footing.
Figure 15
Upon clicking on the isolated footing, users can assign all settings and criteria to isolated footing. One by one users can set Material, Analysis criteria, Post analysis criteria, Sizing and design envelopes to isolated footing.
Concluding Remarks: Till now we have assigned all the design and detailing parameters to Isolated footing. Further step is to perform analysis and design of the Isolated footing.