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:

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 Pile cap Footing.

STAAD File: STAAD File for Example 3

SFA File: Example_3 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). For shallow foundation, this check includes sliding, overturning out of contact and Base pressure checks. For Pile cap, PAC includes pile capacity checks (Compression, Tension and Shear), group pile capacity check and settlement check. 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 PC1 and AC2 should be assigned to PC2 Pile cap Footing. AC1 is the analysis criteria for Rigid footing and AC3 is created for finite element analysis. In the same manner PAC1 is related to analysis criteria AC1 and only assignable to PC1 and as PAC2 is related to analysis criteria AC2, this would be assigned to PC2.

Figure 2

 

Click on the “Show” button beside “Check” to pop up “Stability check” table and assign fators, include or exclude combinations as per your need.

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

If ULS is ticked on (in fig 3) , ULS combinations would also be included in PAC check (ref fig 4). Facility is available to change the Factor of safety (F.O.S) for capacity multiplier and settlement multiplier. Settlement check is possible only in flexible method. For rigid pile caps settlement check is not performed.

Step-2: Create Sizing Criteria

The purpose of defining sizing criteria is to set the maximum or fixed size of the Pile cap Footing. Currently the auto calculation of pile arrangement is available, not the depth. Please refer to snap below to create a Sizing criterion.

We are creating two sizing criteria , SZ1 is for PC1 and it spans from 6 pile to 9 pile. SZ2 is for PC2 and it spans for 4 pile to 6 pile.

 

Figure 5

Here SFA asks user to select among a group of arrangements already available and if one arrangement fails in PAC check, SFA automatically picks up the next arrangement and performs PAC check uptil the list is exhausted or PAC is passed for one arrangement.

Step-3: Create Design Criteria, Detailing Criteria and finally the Design Envelope

This includes the assignment of design and detailing settings for cross section design of Pile cap Footing and performing design.

First step is creating of design criteria. Please refer to snap below -

Figure 6

Element type should be Pile cap 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 Pile cap Footing. refer to snap below showing various design setting inputs.

     Figure 7

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 8

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 Pile cap Footing. refer to snap below,

Figure 9

Reinforcement detailing related settings are available under detailing criteria.

Figure 10

Create Design Envelope:

Figure 11

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 Pile cap Footing PC1 is assigned with design envelope DE1 which includes AC1 Analysis criteria. PC2 should be assigned to design envelope DE2 which includes AC2 Analysis criteria.

Figure 12

Assignment of all settings to Pile cap Footing.

Figure 13

Upon clicking on the Pile cap Footing, users can assign all settings and criteria to Pile cap Footing. One by one users can set Material, Analysis criteria, Post analysis criteria, Sizing and design envelopes to Pile cap Footing.

Concluding Remarks: Till now we have assigned all the design and detailing parameters to Pile cap Footing. Further step is to perform analysis and design of the Pile cap Footing.

In the same manner, create design criteria, detailing criteria and design envelope for pedestals and assign.