• The building model must be completed and analysed, so that the column axial loads and moments are determined. 
  
• The foundation storey (Storey 0) must be set as the current storey. 
  

Pile Cap Insertion

• Select and right click column(s) to access "Insert Pile Cap" at storey 0 via shortcut menu. More than one column may be selected (In this case, the Pile Cap Batch Design dialog will be launched) 
  
• The “Pile Cap” dialog will be displayed. Check the parameters in the dialog and press the “ Design ” button to design the pile cap. 
  
• "Number of piles" can be changed in "Pile Cap" tab if necessary. 
  
• After completing the design of the pile cap, press the "OK” button to close the “Pile Cap” dialog and complete its insertion. 
  

Editing an Existing Pile Cap 

In order to edit an existing pile cap: 

• Select an existing pile cap, 
  
• Right-click and select " Properties " from the menu. 
  
• Modify or auto-design of the pile cap, 
  
• Press the "OK " button in the "Properties" form to update the pile cap. 
  

You can repeat this process to as many members as you wish. One member at a time can be edited by this method. 

Pile Cap Design Scope & Assumptions 

The pile cap design module is intended for single column based on beam theory. 

The pile cap module is not suitable to design a pile cap supporting multiple columns or shearwalls & core walls.  For such situations, it is advisable to use the Piled Raft foundation. 

The design bending moment & shear forces are based on the inverted cantilever method. Example if British Standard is selected, it would be in accordance to BS8110-1:1997 - CL3.11.2.1 and CL3.11.4.3.

For the pile cap section design, it will be categorized as either normal beam ("Shallow Beam") or “Deep Beam” based on the   Reynolds Reinforced Concrete Designers Handbook 11 ^th   Edition – Section 5.8. 

This categorization is based on the ratio of cantilever span/ Effective depth. 

1. If the cantilever span/effective depth > 1.0 , the shallow beam method will be used. 
   
2. If   0.5 <= cantilever span/effective depth <=1.0 , the deep beam method will be used. 
   
3. If   cantilever span/effective depth <0.5 , the section is too deep to be designed, i.e. no solution, and you have to either increase the pile spacing or reduce the pile cap section depth. 
   

When you decrease the bar layers, the average effective depth of the pile cap will be increased as well. Due to this bigger effective depth, you may get   cantilever span / effective depth <0.5 ,   i.e. no solution. 

If the section is categorized as “Deep beam”, the bending moment and shear will be checked according to   CIRIA Guide 2   or   Reynolds Reinforced Concrete Designers Handbook 10 ^th   Edition – Table 148   based on your settings in the option. The default shall be CIRIA Guide 2. 

Pile Cap Properties

The "Pile Cap” properties dialog will be loaded if you select a column/wall in storey 0 > right click > Click "Insert Pile cap". 

The “Pile Cap” properties dialog can also be accessed after selecting an existing pile cap and then by right-clicking and choosing the “Properties” option in the shortcut menu. 

There are three main categories pages in this dialog, namely “Geometry", “Analysis” and “Output”. 

The “Geometry” category page comprises "Pile Cap" and "Pile Location" tabs. 

The “Analysis” category page consists of "Materials", "Options"   and   "Column Loads"   tabs. 

The “Output” category page includes "Axial Loads", "Rebars", "Design Checks", "Report & Detailing", "Result "   and  "Optimization"   tabs.

Pile Cap tab

The following information can be edited in "Pile Cap" tab: 

• Pile Cap Label:  You can enter the label associated with the pile cap in this field. By default, a pile cap label associated with the column label will be generated. For example, “PC-1C1” will be generated if a pile cap for column “1C1” is inserted. 
  
• Number of Piles : You can decrease or increase the pile number by clicking and selecting the required pile number. The checks will be re-performed if this is changed. 
  
• Depth : This is the overall depth of the pile cap. 
  
• Shaft Type : Pile shape can be set as "Circular" or "Square" 
  
• Penetration : Length of the pile penetrates into the pile cap (affects detailing only)
  
• Pile Size :  Pile diameter of circular pile or pile width of the square pile 
  
• Spacing Multiplication Factor Between Piles (Short/Long Dir):   Spacing between the pile in terms of number of diameter of pile. For example, if this is set to 2.5 and the pile diameter is 1000 mm, the spacing between the piles will be 2.5 * 1000 = 2500 mm 
  
• Distance to Face (Short/Long Dir) : Set the pile edge distance for short and long direction. A distance from the pile face to the cap edge smaller than this minimum value will not be used by the program. 
  
• Ultimate Compression/Ultimate Tension : The ultimate compression/ tension capacity of the pile (Factored pile working load) 
  

To check/change the pile capacity of a pile cap, user should check in pile cap properties and should not double click on the pile to open the pile properties directly. Pile Properties is for raft pile design. 

• Column Type :  Column shape can be set to either "Rectangular" or "Circular" 
  
• B1/B2 : B1 and B2 are the horizontal and vertical dimensions of the column on the plan view, respectively. 
  
• Eccentricity X/Y : 
  
  • If "From Pile cap" is selected, the eccentricity of the pile cap with respect to the column in X or Y direction can be edited. 
    
  • If "From Column" is selected, the eccentricity of the column with respect to the pile cap in X or Y direction can be edited. 
    
• Center button: To move the pile cap to the center of the column
  

Pile Location tab

• The auto-calculated pile coordinates in X and Y directions are shown in this tab. 
  
• The offsets of pile in X and Y directions can be edited in this tab. 
  
• The actual coordinates of piles in X and Y directions will be calculated automatically. 
  
• If the pile is selected in the table, the selected pile will be highlighted as "BLUE" in the Pile Cap details on the right hand side. 
  

Pile offsets are meant to be small to take into account site piling in accuracies.  The offsets are not meant to change the pile position and shape drastically.  If the piles configuration differ significantly, then it will be more appropriate to use the Piled Raft Foundation method.

Materials tab

The concrete and rebars materials can be edits in this tab. The unit cost of the concrete, rebars, and pile can be entered in this tab if "Optimization" calculation is required in the "Optimization" tab. 

1. Soil Unit Weight : Enter the unit weight of the fill material in this field. 
   
2. Fill Height : Fill height is the surcharge height. This value is automatically calculated Fill Height = Foundation Depth - Footing Depth.  Value can be over-written. 
   
3. The volume of surcharge will be calculated and multiplied with the "Soil Unit Weight" to yield the additional axial load due to fill material.
   

Options tab

• Base Bending moment calculation method :  
  
  • Cantilever method: All design shear and bending moment will be calculated based on inverted cantilever method.
• Include Effect of Column Dimensions : If this is included, the cantilever span of the pile with respect to the column will be deducted by the column dimensions, i.e. smaller design bending moment and lesser base reinforcement for bending effect. Only applicable to "Deep Beam" theory. 
• Include Effect of Column Dimensions on Shear Span : The effect of column dimensions will be included in shear span if this is checked, resulting in higher shear capacity. Only applicable to "Deep Beam" theory. 
• Include Banding Ratio (Affects Enhanced Shear Capacity) : Check this if you would like to include the banding ratio in the shear design, resulting in lower shear capacity. Only applicable to "Shallow Beam" theory.
• Deep Moment : You can either choose CIRIA or Reynolds method for the deep beam design. 
  
• Check Shear : If this is checked the shear will be designed.
  
• Check Punching Shear : If this is checked the punching shear will be designed.
  
• Preferred Pile Layout For More than 15 piles : You can set this to (i) Single Row (ii) Double Row (iii) Skewed Double Row (iv) Triple Row 
  
• Direction : If you want to rotate the pile cap orientation on plan view, change into direction 1 or 2 based on your preference.
  
• Use Only Selected Direction During Design:   Please check this if you want to use the selected Direction in design. 
  
• Min Pile Cap Depth : The minimum pile cap depth for the pile cap auto design. The program will not attempt to use fewer piles than the minimum entered here. 
  
• Max Pile Cap Depth : The maximum pile cap depth for the pile cap auto design. The program will not attempt to use more piles than the maximum entered here. 
  
• Depth Increment Step:   If depth increment step for the pile cap auto design. For example, if this is set to 100mm, the pile cap depth will be increased by 100mm if the current pile cap depth is inadequate. 
  
• Max. Number of Piles : The maximum number of piles can be provided in the pile cap. For example, if this is set to 100, the pile cap design will stop the design, if the 100 number of pile cap is still inadequate. 
  

 

Column Load tab

The column design axial, shear forces and bending moments can be reviewed or edited in this tab 

• You can change the "Loading"  (drop down list on the right top of this tab) to (i) Envelope (ii) All Combinations or (iii)  User Defined 
  
  • If "Envelope" is set, all combinations will be enveloped for the pile cap design. This will be maximum forces of "All Combination" option & hence more conservative. 
  • If "All combinations" is set, all load combinations will be used in the pile cap design 
    
    • If  you select a load combination > click  Add Selected To User Loads   button, the selected load combination will be added to the "User Defined" Load combination for further editing. 
      
  • If "User Defined" is selected, you can define a new manual design loads, i.e. forces will be decouple from Building Analysis : 
    
    • Click "+Add" button to add a new row  
      
    • You may edit the Comb. No, design axial (N), Shear force in X direction (Vx), Shear force in Y direction (Vy)) Moment in X direction (Mx) and Moment in Y direction (My) 
      
    • Click "X Remove" button to remove a selected row. 
      
    • The final design loading will be auto-calculated in the last column (summation of N) 
      
    • Optionally, you can also click "Import From CSV" button to import the load combination from a CSV file. 
      

 

Axial Loads tab 

Design pile axial forces of each piles (due to the axial load, moment and shear from the column/wall) can be reviewed in this tab. 

1. If you would like to release the moments, one option is to hinge the bottom of the column stump, i.e. hinge bottom of ST01 column. 
   
2. Shear forces in columns are inherent result of lateral forces, such as notional, wind or seismic loads. These cannot be forcefully removed from the building analysis. 
   

The total pile design axial forces are reported in the last column. If the pile design axial force is less than or equal to the pile (ultimate) compression and tension capacities (as defined in "Pile Cap" tab), the texts in the last column will be shown in "GREEN" indicating the pile is adequate in terms of axial capacity. If the pile axial capacity is inadequate, the last column will be marked in "RED". 

All values in the table (except the pile number in the first column and the total in the last column) can be edited if necessary. Then, the total pile design axial force will be recalculated automatically. 

Re-calculate Axial Loads button is used for resetting all user defined values in the table and recalculating the pile axial loads. 

 

Rebars Tab

The auto-designed reinforcement can be reviewed in this tab in a table format, including the values of As provided and required. 

The description of the rebar table are as follows : 

1. Base (X & Y) :  These are bottom rebars in both direction which are auto-designed based on design moment. 
   
1. The area of steel provided (As-prov) & required (As-Req) are shown. 
   
2. Side (X & Y) :  These are the side bars. They are not designed  & is provided as good detailing practice. 
   
3. Top  (X & Y) : There are the top rebars in both direction.  They are not designed & is provided as good detailing practice. 
   
1. This field is only active if option Use Top Bars is checked.

1. User may adjust the rebar diameter & spacing. 
2. For example, user can manually increase the steel bar diameter or decrease the spacing if the steel is reported to be insufficient. The design is automatically re-checked, if ENTER is pressed or other cells are clicked after the change. 

1. Auto-select Reinforcement : Allows you to auto re-design & reselect the pile cap reinforcement.  This is recommended after manually adjusting other parameters of the pile, example pile cap depth. 
   
2. Use Top Bars : If checked, this rebar will be shown in the rebar table & included in the detailing (no design).
   
3. Use Shear Reinforcement : If checked, this rebar will be shown in the rebar table & included in the detailing (no design).
   
4. Number of Layers (X/Y) : Specifies the number of layers of base / bottom rebar.
   
1. By default, the auto design will only provide 1 layer.  
   
2. Manually increasing the number of layers more than 1 will increase the total provided base steel & improves the design checks that depends on this rebar. 
   
3. Generally, for Deep Beam method, the pile cap may require more than one layer of base reinforcement to satisfy the Distribution Depth Check in the Design Checks tab. 
   
5. Layer Spacing (X/Y) :  Specifies the spacing of rebars between bottom steel layers if number of layer is more than 1.
   
6. Internal Bending Radius :  Specifies the internal bending radius of base reinforcement. 
   
1. This directly affects the Maximum Bearing Stress check in the Design Checks tab.
   
2. Increasing the bending radius will improve the Maximum Bearing Stress check.

Concrete Cover : Top, bottom and side concrete covers are shown & can be edited.

 

Design Checks tab & Guidance on Manual Design

The pile cap auto-design will automatically design the pile cap shape, size, depth and the number of piles.

• Pile Capacity Check : If this is "tick", it indicates the pile capacity is adequate. Otherwise, it will show "cross" if the design is failed. 
  
• If this check fails, try increasing the number of piles manually
  
• Go to the Axial Loads tab to see details of this check. 
  
• Generally, increasing the number of piles will improve all other checks since each pile force is decreased.
  
• Base Design Moment : Shows the base design moment in X and Y directions 
  
• Bending Design Result : If this is "tick", it indicates the base reinforcement design is adequate. Otherwise, it will show "cross" if the design is failed. 
  
• If this check fails, try increasing the base rebar in the Rebars Tab. 
  
• Design Shear Force : Shows the design shear force in X and Y directions 
  
• Distribution Depth Check : Bar distribution check for the deep beam method ONLY 
  
• If this check fails, increase the "Number of Layers" of rebar in the Rebars Tab. 
• Column Base Face Perimeter Shear Stress Check : Shows the design shear stress at the column face against the shear stress capacity at column face. 
  
• If this check fails, as trial, increase the column stump size in the Pile Cap tab.
  
• Once finalized, that column size in ST01 should be updated in the model and Building Analysis re-run to obtain updated forces (as increasing stump size will also affect the weight & stiffness of structure). 
• Shear Capacity (Shallow/Deep) : The first value is shallow beam shear capacity while the second value is the deep beam shear capacity.  
  
• Design Shear vs Shear Capacity : Shows the column design shear and shear capacity.  This check can be manually improved by : 
  
• Increasing the pile cap depth in Pile Cap tab.
  
• Increasing the base rebar in Rebars Tab. 
• Longitudinal Rebar Shear Check : Longitudinal shear check will only be performed for "Shallow Beam" case. (i.e. non Deep Beam case).  If this check fails, it can be improved by  :
• Increase the pile cap depth in Pile Cap tab. 
  
• Increase the Base rebars provided in the Rebars Tab. 
  

• Punching Shear Check Perimeter (1/2 ): This checks for punching shear for the first and second punching shear perimeter check if applicable.  This check can be manually improved by : 
• Increasing the pile cap depth in Pile Cap tab.
  
• Increasing the base rebar in Rebars Tab. 
  
• Max. bearing stress :  It checks the base reinforcement bearing stress. 
  
• The bearing stress is a minor detailing check. 
  
• This is not automatically designed, i.e. user should specify the correct bending radius of the rebar in the Rebars Tab. 
  
• To improve / reduce the bearing stress, you can increase the “Internal beading Radius” manually in the Rebars Tab. 
  

In performing manual design, if adjusting many of the above parameters does not work, try one or combination of the following :

1. In Options tab, try changing the design parameters. For example, checking "Include Effect of Column Dimensions" generally improves moment & shear checks. 
   
2. In Pile Cap tab, try increasing the number of piles. This will generally improve many of the design checks since each pile force is reduced.
   
3. In Pile Cap tab, try increasing the pile capacity so that less number of piles & a smaller pile cap is required. 
   
4. In Materials tab, try increasing the Concrete grade, which generally increase all capacities. 
   

 

Report & Detailing tab

Report can be created by clicking the Create Report button in this tab 

The following options can be checked if necessary: 

• Add column effects to reports for all combinations 
  
• Add pile axial loads for critical combination to report 
  
• Add pile coordinates table to report 
  
• Show Only critical combination results/ Show All combination results 
  

 

Results Tab

 

Optimization tab

This tab allows you to perform cost analysis/optimization by listing additional candidates for the pile cap. 

It will increasing the pile cap depth or pile number. Then, the total cost of different candidates will be calculated automatically for comparison. 

The min. pile cap depth, depth increment step and max. number of piles can be set in the   Options   tab. The unit rates of concrete, rebars and pile can be edited in   Materials   tab.

Show Graphic   toggle button allows you to switch between the table to chart view or chart to table view 

Max. # Of optimization candidates : Enter the number of candidates to be generated. 

List Candidates   button: If this is clicked, it will generate different candidates for the pile cap 

If you would like to adopt a case of the listed candidates, please DOUBLE CLICK the row of the pile cap in the table. Then, the pile cap geometry and calculations will be updated accordingly. 

Pile Cap Batch Design 

If multiple columns are selected > Right click > Click "Insert Pile Cap",   Pile Cap Batch Design   dialog will be launched for designing the pile cap in batch mode. 

By default, all select columns will be associated to a row of pile cap in the Pile Cap Batch Design dialog. 

The  Pile Cap Batch Design  dialog consists of top and bottom panels: 

• Top Panel:  A row of buttons for various functionality as described below 
  
  • Design All: Allows you to design all the pile cap automatically 
    
    • Option 1: Check Design (Do not redesign) - if this option is selected, the pile cap design will only be checked and no modification will be made for the existing pile cap geometry and reinforcement. 
      
    • Option 2: Check Design (Redesign if fails) - if this option is chosen, the pile cap will only be redesigned if it fails. 
      
    • Option 3: Redesign All - this option will reselect/redesign the exisitng pile cap regardless the pile cap is pass/fail. 
      
  • Design Selected: Allows you to design for the selected pile cap in the table (in the bottom panel) 
    
  • Group Selected: Group the selected pile caps in the bottom table 
    
  • Group by Piles: Group the pile caps based on the pile numbers. The pile caps shall be designed for at least once if this button is clicked. 
    
  • Ungroup: Ungroup the selected pile caps 
    
  • Select\Clear All: Click to select all pile cap or unselect all pile cap 
    
  • Reverse Selection: Allows you to reverse the selection in the bottom table 
    
  • Foundation Settings : Allows you to set the default foundation settings for the pile cap 
    
  • Design log : Shows you the design processes. You can check this log if you want to find out why the pile cap design fails. 
    
  • Import From CSV :   Allows you to import the pile cap(s) from a CSV file. 
    
  • Export to Excel: Allows you to export the bottom table to an excel file 
    
  • Pile Cap Design Report:   Allows you to generate the pile cap design report. 
    
  • OK : Click to accept the pile cap design 
    
  • Cancel : Click to discard the pile cap design 
    
• Bottom Panel: A table consists of pile cap(s) design information 
  
  • Label: The label of the pile caps 
    
  • Columns : The column label which is associated with the pile cap 
    
  • No. of piles: The number of piles in the pile cap 
    
  • Pile Size: The pile size or diameter of the pile cap 
    
  • Depth: The depth of the pile cap 
    
  • Spacing Sx/Sy:  The pile spacing in directions X and Y 
    
  • Lx: The pile cap width in X direction 
    
  • Ly: The pile cap length in Y direction 
    
  • Base X/Y: The base reinforcement in X and Y Directions 
    
  • Top X/Y: The top reinforcement in X and Y directions 
    
  • Side X/Y: The side reinforcement in X and Y directions 
    
  • Shear: The shear reinforcement 
    
  • Design Status: the pile cap design status. If the design pass, a "tick" will be marked. Otherwise if design fails, a "red cross" will be marked. 
    

 

You can design pile cap to service load (unfactored load): Design Pile Cap/ Pad Footing for Service Load (Unfactored Load)