Create pile caps

A pile cap is an isolated piled foundation that supports a single column.

Note:

Before you can create pile caps, the Pile Catalogue must contain at least one pile type.

To create pile types, see Create a pile type catalogue.

Create pile cap under a specific column

On the Foundations tab, click Pile Cap Column.
In the Properties window, adjust the pile cap properties according to your needs.
Click anywhere in the column under which you want to place the pile cap.

Tekla Structural Designer places a pile cap under the selected column.

Create multiple pile caps

On the Foundations tab, click Pile Cap Column.
In the Properties window, adjust the pile cap properties according to your needs.
Move the mouse pointer to a corner of an imaginary box that will encompass the columns under which you want to place pile caps.
Hold down the left mouse button.
Drag the mouse pointer to the opposite corner of the box.
Release the mouse button.

Tekla Structural Designer places pile caps under all columns within the box.

Create a user-defined pile arrangement

If necessary, you can modify the pile arrangement in a pile cap and create user-defined pile arrangements. Creating user-defined pile arrangements can be particularly useful when you want to check a pile cap where the pile positions on site do not exactly match the originally specified arrangement.

Do the following:

In the model, select the pile cap that you want to modify.
In the Properties window, go to Pile arrangement.
Click the ... button next to Pile arrangement.

The Pile Arrangement dialog box opens.
In the Pile Arrangement dialog box, select the User Defined Arrangement option.

Note:
If the Auto-design piles option is selected in the Properties window, Tekla Structural Designer asks you whether you want to turn off the option. Click Yes.
Specify the pile arrangement properties according to your needs:
1. Select the pile type.
2. Define the pile length and width.
3. If necessary, define the eccentricity of the pile cap centroid from the centroid of the column it supports in X and Y directions.
Tip:
To add more piles into the arrangement, click Add.
If necessary, in the table below the properties, adjust the position of piles by defining the eccentricity of the pile centroid from the pile cap centroid.
Click OK.

Tekla Structural Designer creates the pale arrangement that you defined.

Override the loaded area to be used in the pile cap punching check

When you create a pile cap, initially the punching shear loaded area is based on the area of the column section being supported. If you require the punching check to consider an unmodeled base plate or pedestal you can do so by specifying a User loaded area as follows:

Select the pile cap.
In Properties window, go to the Foundation Parameters section and select User loaded area.
Specify a Loaded Area Breadth and Loaded Area Depth appropriate to the base plate or pedestal.

Pile cap properties

Select one or more pile caps and then use the Properties window to view and modify their properties.


Property	Description
General
Foundation Type	Isolated Pile Cap (not editable).
Auto-design depth	• When Autodesign is selected an iterative procedure is used to determine the depth. If the shear design fails the depth is increased until either the check passes, or the maximum depth specified in Design Options has been reached. • When Autodesign is not selected (i.e. check mode), the existing depth is retained and Tekla Structural Designer determines if it is sufficient. Note: In Design Options - if Isolated Foundations have been set to be designed using groups, then if at least one base in the group is set to have its depth auto-designed the whole group will have their depth auto-designed. Note: When Design Member on the right-click context menu is used to design an individual base, the depth will be checked or designed according to the auto-design depth setting.
Auto-design piles	Autodesign piles automatically determines the quantity and size of piles. Cleared - the specified number of piles at their specified positions will be checked during the design process. Checked - the number of piles and their positions under the pile cap will automatically determined during the design process. When this checkbox is selected, the actual procedure used will depend on the Pile auto-design method that has been specified in Design Options > Concrete Foundations > Isolated Foundations Piles The Minimise number of piles method commences by first selecting the pile with the smallest load capacity in the Pile Catalogue. Pile positioning is attempted using the user defined pile arrangements. If one of the limitations is exceeded the pile with the next smallest load capacity in the catalogue is selected and the process starts again. This is repeated until the pile loading check passes. The Minimise pile capacity method commences by first selecting the pile with the smallest load capacity in the Pile Catalogue. Pile positioning is attempted using the user defined pile arrangements. If one of the limitations is exceeded one pile is added to the pile group and the process starts again. This is repeated until the pile loading check passes.
Select size/depth starting from	This option only appears when either Autodesign depth is selected. It sets the autodesign start point for the depth, or size, or both. The options are: Minima (default) Current Selecting ‘Minima’ removes the current depth/size and begins with the minimum allowed depth/size specified in Design Options. For both options the auto-design depth increment is that specified in Design Options> Foundations Isolated Foundations> Foundation Size
Autodesign reinforcement	This setting applies to top and bottom reinforcement, but reinforcement in either location can still be set to none. If enabled, auto-design of reinforcement occurs after the base size and depth have been established. When Autodesign reinforcement is enabled an iterative procedure is used to determine the reinforcement. If the bending design fails the reinforcement size gets increased and spacing gets decreased until these checks pass. Iterations continue until either a satisfactory bar configuration has been achieved, or the maximum bar size and minimum spacing specified in Design Options has been reached. At this point the depth gets increased and the above procedure is repeated. Note: If the smallest bar at largest spacing is insufficient then the next bar size at max spacing is used. If the largest bar is reached the spacing gets reduced and the smallest bar is used. Then the bar size gets increased until the largest bar size reached. When Autodesign reinforcement is disabled (i.e. check mode), the existing reinforcement provision is retained and Tekla Structural Designer determines if it is sufficient. Note: In Design Options - if Isolated Foundations have been set to be designed using groups, then if at least one base in the group is set to have its depth auto-designed the whole group will have their reinforcement auto-designed. Note: When Design Member on the right-click context menu is used to design an individual base the reinforcement is always designed (irrespective of the Autodesign reinforcement setting).
Select bars starting from	This option controls the starting point for auto-design procedures and is therefore only displayed if Autodesign reinforcement is selected. Minima (default) - removes the current arrangement and begins with the minimum allowed bar size specified in Design Options. Current - the auto design commences from the current bar arrangement.
Foundation Parameters
Geometry type	Specifies the base shape.
Eccentricity in Y direction	Specifies the eccentricity of the pile cap in the Y direction. (For strip bases this is along the wall)
Eccentricity in X direction	Specifies the eccentricity of the pile cap in the X direction. (For strip bases this is across the wall)
Rotation angle	Specifies the rotation of the pile cap relative to that of the support (which is controlled by the rotation angle specified for column).
Length in Y direction	Specifies the size of the pile cap in the Y direction.
Length in X direction	Specifies the size of the pile cap in the X direction.
Depth	Specifies the depth of the base.
Concrete class	The concrete grade. The concrete grades that are available are set from the Materials button on the Home ribbon.
Use loaded area	Selecting this option allows you to specify a user override of the punching shear area - defined using the Loaded Area Breadth and Loaded Area Depth properties. This feature can be used in both pad bases and pile caps to, for example, consider unmodeled base plates or pedestals.
Use Permanent load ratio (Eurocode only)	You are required to supply a value for the permanent load ratio parameter. A default of 0.65 has been assumed, but you are advised to consider if this is appropriate and adjust as necessary.
Maximum crack width	• 0.2 • 0.3 • 0.4
Piles
Pile type	Pile types that have previously been specified in the Pile Catalogue are available for selection. You can choose <New...> to add additional types.
User defined arrangement	Specifies the eccentricity of the pile cap in the X direction.
Pile arrangement	Opens the Pile arrangement dialog for specifying the number of piles, and spacing, pile type and principal direction.
Number of piles	Specifies the number of piles.
Principal direction	Specifies the principal direction.
Pile spacing	The dimension between pile centers.
Shape	For three piles only, you can choose to specify either a triangular. or rectangular pile cap.
Reinforcement
Type	• Mesh • Loose Bars • None
Rib type (Head Code Eurocode, BS or IS)	• Plain • Type 1 • Type 2
Rib type (Head Code ACI)	• Plain • Deformed
Bar type	The reinforcement grades that are available here are set from the Materials button on the Home ribbon.
Bar size, spacing, Mesh type etc.	The actual reinforcement provided in each of the layers is indicated here.
Top, Bottom, Side cover	Nominal cover to reinforcement.
Soil Parameters
Soil unit weight	Soil unit weight
Characteristic friction angle	Characteristic friction angle
Presumed bearing resistance (EC Head Code)	The presumed bearing resistance is only displayed and used when the ‘presumed bearing capacity method (EN 1997 - 1 cl. 6.5.2.4)’ is selected in Design Options.
Surcharge
Soil Surcharge depth Other permanent Permanent surcharge load Other variable Variable surcharge load	Drop-list controls allow each surcharge load to be assigned to a specific loadcase. The partial safety factors defined in the design combinations for these cases are then used for these loads in all design calculations. The assigned loadcases are initially set to “None” and must be user-selected. Where no appropriate Dead or Live loadcase exist in the model and so no loadcase can be assigned, zero partial factor values are used in the calculations.
Design shear strength of soil angle (ACI & BS Head Codes)	Design shear strength of soil angle
Allowable bearing capacity (ACI & BS regional codes)	Allowable bearing capacity
Bearing capacity A1 - STR (EC Head Code)	Allowable bearing capacity A1. Only displayed and used when the ‘presumed bearing capacity method (EN 1997 - 1 cl. 6.5.2.4)’ is unselected in Design Options.
Bearing capacity A2 - GEO (EC Head Code)	Allowable bearing capacity A2. Only displayed and used when the ‘presumed bearing capacity method (EN 1997 - 1 cl. 6.5.2.4)’ is unselected in Design Options.
UDA	A customizable list of the attributes that can be applied to individual members and panels.