Pile cap Tab

This is a floating tab and not present in the top ribbon by default. When a pile cap is selected, this tab appears in top ribbon. Various options for pile cap editing, analysis, design, review etc are available under this tab and are explain in detail.

Alter-

It provides various options to edit an existing pile cap geometry or adding multiple pile caps. This first group features simple transformations that treat the Pile cap as an integral unit-
a) Move
b) Clone
c) Repeat
d) Mirror

All these transformation tools can be accessed by selecting the pile cap/ pile caps and right clicking.

Simple Transformations-

1. Move-

“Move” shifts the entire Pile cap by translation. The two options are

1. Move With Reference
2. Move By Distance

1. Move With Reference- You can shift the pile cap graphically by clicking the starts and end points in the schematic area or enter their coordinates in the “Move With Reference” window. Click “Apply” to execute the operation. In the snap below, the existing pile cap is being shifted from reference point (X = 0, Z = -2) m (as shown in “Move With Reference” Window) to another point (X = 0, Z = 3). User may shift by direct input of source and destination coordinates at “Move with Reference” window, or by picking source and destination coordinates through mouse click at view area. If these two points are picked by mouse click, the coordinates at “Move With Reference” Window would get automatically updated. Hit “Apply” button at “Move with reference” page to execute.

2. Move By Distance-

You can enter the shift in the X and Z directions in the “Move” window. As before, click “Apply” to execute the operation.

If you click the arrow next to “By Distance”, two further options are shown. The second option is to move by angle, as shown below.

Note that by default setting, the “Move” windows and any windows corresponding to any operation are displayed at the lower right corner of the main window, but you can change this setting.

2. Clone-

The Clone transformation works in the same way as “Move With Reference”. You either click and select where to copy and paste the pile cap or enter the parameters in the “Clone” window. If you prefer to use your mouse, the table in the “Clone” window would be automatically updated. As before, click “Apply” to execute the operation. Click “Cancel” to kill the operation.

3. Repeat-

The Repeat transformation creates multiple pile caps a single operation by copying one original pile cap at any angular direction at a user-defined offset. In the screenshot below, three new pile caps are created (drawn with broken lines) at an angle of -90 degrees and an offset of 3 m. As before, click “Apply” to execute the operation.

4. Mirror-

The Mirror transformation copies a pile cap into a mirror image of it. You pick two points to define the mirror line either by clicking in the drawing area, or by entering the coordinates of the points in the “Mirror” window. When you click the two points, their coordinates automatically updated in the “Mirror” window. The new Pile cap, which is a mirror image of the original one reflected at the mirror line, is drawn with broken lines in the figure. As before, click “Apply” to execute the operation.

 

Modify-

These options are for Further Transformations and this second group features further transformations to the shape of the Pile cap:

Currently only one option is available, “Delete”-

1. Delete-

You can select and delete any Pile cap. Select the Pile cap and click the “Delete” button on the keyboard or select the Pile cap, right click, and then click “Delete”.

Action-

It covers four items-

1. 1. Perform Analysis
   2. Post Analysis
   3. Calculate Configuration
   4. Perform Design

 

All these options are available under different tabs and already explained in details for Mat, Isolated footings. So, only a very brief description is added.

 

1. Perform Analysis-

This feature is available under “Analysis” tab, and also can be accessed through right click, and explained in detail in Analysis document. Here same feature is available and explained very briefly. Click “Perform Analysis” and the selected Pile cap would be analysed. Pile cap analysis can be done either as Rigid Body or as flexible (FEM). This decision is taken while creation and assigning of the “Analysis Criteria” is done. For FEM, the analytical model is created and STAAD Pro engine is used to analyse the Pile cap. For Rigid Body Method, separate dedicated engine is used to calculate pile reactions by using bolt theory.

 

If no concrete grade is created or assigned, then the following pages would pop up sequentially for quick addition and assignment of Concrete type. Select Country code and Concrete Grade ,Click “Add Concrete Grade” and then in the next pop up page click “Assign and Analysis”.

If no “Analysis Criteria” is defined, then another page “Perform Analysis” would appear. To define analysis method (Rigid or FEM), include /exclude Load combinations for analysis and for handling different soil/ buoyancy effect, click “Select” (as shown in the snap below) to open “Load Combination” page. Click “OK” to finalized load combinations and click “Create Assign and Analysis” button to perform analysis. These pages are explained in detail in Analysis document of Mat and Isolated footing.

2. Post Analysis-

This button gets activated once analysis is performed successfully. Hit this button to perform post analysis for service checks  that include Pile Capacity Checks (Shear, Compression, Tension), Pile Group Capacity Check in compression and Pile settlement check (Pile settlement check is possible only in flexible method).

To perform this task, post analysis criteria should be created and assigned to the pile cap. If that is not already available, then SFA would pop up the following page for quick creation and assignment of post analysis criteria. This is explained in detail in the Post Analysis Checks and Design document of Mat and Isolated footing.

3. Calculate Configuration- Pile cap Arrangement can be done with different configurations. SFA Provides a list of templates for different configurations, and while creating a pile cap, one configuration is picked up. If Post analysis check is performed and found passed, then no configuration change is needed. If Post Analysis check is failed, then user can either manually change into higher configuration and perform PAC check until passed, or this option “Calculate Configuration” is used for automation. Here user needs to keep a list of configurations selected and SFA perform checks and switches into higher configuration automatically until PAC check is passed. To avail this feature, users need to create and assign sizing criteria. If sizing criteria is not available (created and assigned already) then a pop-up page “Create Plan Size” would appear and ask user to create and assign a sizing criteria. To control the configuration list, click on “Select” beside “Parameters” to pop up another page “Select Optimization”. Here the configuration list can be optimized. In the snap below, we can see that 6 to 15 pile arrangements are selected. So, when “Calculate Optimization” button is hit, SFA would perform all configurations starting from 6 to 14, till the PAC is passed. Once PAC is passed, that configuration will be finalized.

4. Perform Design- This button gets activated once analysis is performed successfully. Hit this button to perform Design checks (Flexure, Punching, one way shear checks etc.). To perform this task, Design Criteria, Detailing Criteria and Design Envelope should be created and Design Envelope should be assigned to the Pile cap. If that is not available, then SFA would pop up the following pages for quick creation and assignment of Design Criteria, Detailing Criteria and Design Envelope. This is explained in detail in the Post Analysis Checks and Design document.

For analysis, Concrete grade is mandatory, which is already created and assigned. For design, along with Concrete grade, Steel grade is also needed. If no steel grade is created and assigned SFA would pop up following page and quickly create and assign steel grade.

If no “Design Criteria” is defined, then another page “Perform Design” would appear.  It helps to select country code. Hit “Create Design Criteria” and next, SFA would quickly create a detailing criterion through pop up page with the already available detailing criteria (If no detailing criteria is available). Hit “Create Detailing Criteria” and Next pop-up page would quickly create a design envelope for the available design and detailing criteria. Hit “Create Assign Design Envelope” button to perform design the pile cap for this envelope.

already available detailing criteria (If no detailing criteria is available). Hit “Create Detailing Criteria” and Next pop-up page would quickly create a design envelope for the available design and detailing criteria. Hit “Create Assign Design Envelope” button to perform design the pile cap for this envelope

Analysis results-

This provides different tools for viewing analysis results-

1. Contour
2. Analysis Output
3. Cut Line

 

1. Contour-

This is also available under “Analysis” tab and explained in detail. It shows different pile reactions (Compression, Shear or Tension) , in color scale.

You need to pick up the Load Combination and the type of output (Compression, Shear or Tension) you want to see and click upon “Contour” to generate the contour for that particular output and for that particular load combination.

In the snap below, Pile Compression contour is being shown for load combination 10.

 

Analysis Output -  It opens the ANL file which is generated as the output from the STAAD Pro analysis of the analytical model. It works only for Pile caps analyzed in FEM. For Rigid Analysis ANL file is not provided, as no staad engine is fired.

3. Cutline- This is a powerful feature to draw a line on a foundation and generate stress values along that line using it as a cut -section. It’s explained in details in another document named Cutline . This feature is also available only for Pile caps analyzed in flexible method (FEM).

Post Analysis Check Results-

This option displays a few Post Analysis result in contour form. So, this would be effective only when Post Analysis Check is executed successfully. If you expand this drop down, you will observe five options, -

1. Pile Compression Capacity Envelope
2. Pile tension Capacity Envelope
3. Pile Shear capacity Envelope
4. Critical FOS
5. Pass/Fail

Click “ Pile Compression Capacity Envelope” and Click on “View result” Button. The contour would be generated for Pile Compression Capacity Envelope.

Suppose we have run post analysis for service cases only and service case envelope covers 14 SLS load combinations, then SFA is having pile reaction datasets for 14 SLS cases each of which contains pile reactions at each pile. Now for each load combination, for each pile, we can calculate capacity ratio as pile compression Force/ factored Pile capacity. So, for each pile, we can calculate critical capacity ratio for this SLS envelope (minimum capacity ratio at this pile point among these 14 SLS load combinations). If we perform this task for all piles, then the SLS pile compression capacity envelope would be available. The snap above is showing the same data in contour format. In the same manner shear and tension capacity envelopes can be calculated and displayed.

 

Critical FOS- This option shows the critical among all FOS for all PAC check. Here in the snap below, we can see the value reported as 1.94. If we review this data with post analysis check summary, (in the table), FOSs available are 1.94 for compression, 13.69 for shear and >1000 for tension. SO, compression is the critical condition here and compression FOS, which is 1.94 here, is displayed as critical FOS.

 

Pass/ Fail- To give user information at a glance (through color coding) whether the PAC check is passed or failed.

Design results-

It provides various options to view results after design.

a) Strip X/Y

b) Strip Forces

c) Punching

d) TX/TY/BX/BY Design results

 

1. Strip X/Y- This is available after successful design of a footing. Strips are created based on the user’s settings and detailing requirements for design. Upon clicking on this button, Strips are highlighted on the pile caps. Strips details are presented along X and Y directions of the pile cap. For other footings X and Y strips are generated as per the defined width. For pile caps, the whole width is considered to generate a single strip, as in reality pile caps are provided with uniform mesh.

By default, The strip width is 1000 mm or 1 ft (until the size and shape of the footing forces to compromise at last strip) for all modules and in Pile cap the strip width is the total width of the foundation (that means , for pile cap only a single X strip and a single Y strip are present.

 

2. Strip Forces- It shows Moment and Shear (M and V) for any strip in graphical form. In other words, it provides us the SF and BM diagram of this strip, if we consider this strip as if an “independent combined footing supported on a series of piles”, or if we draw a cutline along the centerline of this strip, the SF and BM diagram effective for this  strip along this line is being displayed here.

 

It picks up a number of points on the strip along the centerline, calculates Shear and moment at those points (for the current load combination) and draws the graph.

If a strip is aligned parallel to the global X axis, then this moment would be MZ moments at the control points (as shown in the snap below) and the shear would be the shear on this strip in global YZ-plane.

 

Click on Strip X or Strip Y first and then click upon “Strip Forces” icon and  the graph view would appear showing M and V for current load combination.  In “Strip forces” graph view window, click the first icon to expand the load combination and select the load combination as current, for which M and V graphs would be displayed. Expand the second icon to tick untick M and or V for display. Third and fourth icons are for activation of horizontal and vertical grids respectively. The fifth icon is for switching between line segment graph or smooth curve graph. Sixth item is for saving the graph for future access. Seventh icon is for popping up “setting” options. The snap below explains each icon. At top of “Strip Forces” window, current load combination is also displayed.

 

Advance Options- It contains three items-

1. Segment length
2. Calculation Point Count-
3. Calculate for Section Width

They are already explained in detail in Dynamic menu Mat Document.

3. Punching-

Punching search radius and Punching Perimeter are presented upon clicking this button. Check whether Program defined search radius is not sufficient to identify the correct punching width and if found insufficient, user can change punching radius and instruct SFA to recalculate.

Punching Shear Check is a major design check and explained in detail in the document named as “Post Analysis Checks & Design”. Punching check is done for isolated and combined at column locations only. In Pile cap, punching check is done both at column location and pile locations.

 

 

4. TX/TY/BX/BY Design results-

This is also a major design topic and explained in detail in “Post Analysis Checks & Design” document. Here only a brief discussion is available.

SFA performs flexure check and provides flexure reinforcement in four layers- Top X (TX), Bottom X (BX), Top Y (TY) and Bottom Y (BY). Once design is successfully performed, these options can be used to view reinforcement, moment capacity and various other design outputs. Click on “BY” and select and design result from drop down arrow. Suppose let’s look at “design” (default item). Modelling windows would graphically show the design result.

In the picture below, we can see that SFA has broken the whole Pile cap into small design strips and designed each strip. Now reinforcement is optimized accordingly. In the picture we can see, for top reinforcement, only #13 @ 150 mm c/c reinforcement is sufficient everywhere.

 

Another snap below shows, reinforcement detailing along Bottom Y.

In the same manner, other options like Ast required, Ast Provided, Moment Capacity, Extra Rebar, Zone can also be used to view design results. For more details, please refer “Post Analysis Checks & Design” document.