Last modified by Linus Karlsson on 2024/05/27 14:28

An IMPACT definition is a combination of a Revit family (loadable family for hollow cores) and different settings which together enables the IMPACT user to draw elements and at the same time get automation, e.g. automatic lifters.

To access the hollow core definitions, go to IMPACT - Elements - Hollow Cores. On the project level, there is a definition called '19' prepared for this course. Select the definition and press 'Edit'.

hc def.png

Figure 1. Select hollow core definition.


The first tab of the definition contains information about the outer boundary for the geometry as well as a few settings. 

To configure the geometry, there are two ways; either load a family that we have prepared, or creating the definition and family by using a cross-section.

For the second option, we need to prepare a cross-section of lines on one of the levels. This since the cross-section for hollow cores differ a lot and it's not possible to set up a generic cross-section type. In this, we can also highlight where the hollow core can be cut as well as strand positions. 

hc def 2.png

Figure 2. Example of cross-section of lines.

To configure the boundary, click on 'Pick section' and select the boundary lines. End with 'Finish'.

hc pick section.gif

Figure 3. Pick section.

The section is now added to the definition, and the values for height, width, and section geometry is automatically added to the definition from the geometry that we just selected. 

hc general.png

Figure 4. General tab.

We need to add an eventual tolerance (1) to the hollow core. E.g. if the width is 1200mm and the tolerance is 2mm, the actual width of the finished hollow core will be 1196mm, but it will still have the theoretical width of 1200mm in IMPACT.

We also need to add a value for the difference between the bottom and top (2) of the section. This is so the setting in IMPACT Project Manager to see either the bottom or top of the hollow core can work. 

Select a material (3) for the definition. 

hc def material.png

Figure 5. Select material.

Select a production line (4) so that when we draw the elements, we will be sure that they can be produced. With the production line configured, IMPACT will give warnings to the user if an element is too long, wide, high, or heavy for production.

hc def mould2.png

Figure 6. Production line.

Opposed to the previous element type definitions, we need to wait with creating the family (5) for the definition until the cores are configured. We cannot select default endcaps (6) until the family is created. So let's go to the next tab. 


Here, we need to create the cores for the cross-section. Click 'Cores' and pick the origin (lower left corner), then select each core one by one with clicking 'Finish' in between each core. When all cores are selected, end the selection by clicking 'Esc' on the keyboard. 

hc pick cores.gif

Figure 7. Select cores.

The button 'Show core extents' will preview a rectangular boundary around each core. 

hc core ext.png

Figure 8. Show core extents. 

The geometry configuration is now done, so it's time to generate the family. Go back to the 'General' tab and click 'Create Family' (1). It's also possible to select an endcap. 

hc generate fam.png

Figure 9. Create family.


In the cutting tab, we can decide where IMPACT will make the cut in partial elements. Click 'Select cut zones' and start with picking the origin. Continue with selecting the cut zones by picking first the left point and then the right point of each zone. End the selection with clicking 'Esc' on the keyboard.

hc pick cut.gif

Figure 10. Select cut zones.

When the cut zones are selected, we need to decide the cutting method (1); left, right, or symmetrical. This will decide which side the cut is done on a partial hollow core slab. 

'Use nearest cut zone when cutting elements' (2) means KoLLA.

The cut zones can also be added manually (3). 

hc cut.png

Figure 11. Cutting. 


The strands needs to be configured as well. Click 'Select strands' and pick each strand position. End the selection with clicking 'Esc' on the keyboard.

hc pick strand.gif

Figure 12. Pick strand positions.

The strands can be divided into different groups (1). The groups can later be used to configure different diameters, wire qualities, and prestress forces. Assign a strand to a group by selecting the group from the drop down list (2). 

hc group.png

Figure 13. Configure strand groups.


All strands won't be used for all hollow cores. To decide which strands to use in each case, we can build up a set of 'strandpatterns' (1) where one pattern will be default (2). A strandpattern is a combination of different strands (4) with different diameters, wire qualities, and prestress forces (3). 


Figure 14. Strandpattern. 


To get automated lifts, we need to configure which cast-in materials to use, as well as a set of rules of how and when they should be used.

Byt ut efter case 133708

hc lift3.png

Figure 15. Lift settings.

  1. Since the shape of the long sides of hollow cores comes from the mold, almost all hollow cores will have an identical profile that can be used to lift the hollow cores. This means that most hollow cores won't need any lifters. The setting lets the user decide if lifters should be added automatically or manually to the hollow cores. Usually, it's set to 'Manually'.hc lifter.png

    Figure 16. Hollow core lifted in the side profiles.

  2. Configure rotation of the lifters.
  3. There are only two options for inserting lifters in a hollow core slab; two or four lift points. If two points are used, the lifts will be inserted diagonally in the slab (see Figure 17). 
    slab def lifts 2 or 4.png
    Figure 17. Number of lifts.
    With the default lift types, you can configure two or more setups of cast-in materials, and select which setup should be the default one. An example is the lift angle. The lifters in Figure 15 above are configured for a lift angle of 60°. If the same lift should be used with another lift angle, it should be able to handle more or less mass.
    slab def lifts type.png
    Figure 18. The same lifter with two different lift angles.
  4. We already know that an element can have two or four lifters inserted. Normally, these two differ in lift type and capacity. To solve this, we have two configurations of cast-in materials to be used as lifters. One for each number of lifts used. 

    Figure 19. Select the number of lifters to configure.
    slab def lifts number of lift.png
    In the configuration of the cast-in materials, the family types are selected and the user decides which lift type (e.g. lift angle) this component should be used for. The max capacity of mass is also added. This information is used in combination with the rules in section 1 above to optimize which and how many lifts are used in each element. In this slab definition there is only one cast-in material available to use as a lifter due to the thickness of the slab. 
    slab def lifts list.png
    Figure 20.  List of cast-in materials.
  5. In the top right area, the user can decide how the lifts should be placed in the length and width direction. There are three options:
    1. Fixed distance - placed with a fixed distance from the side of the element.
    2. Part of length/width - placed with a distance depending on the length of the element. 
    3. Center of gravity - placed according to the center of gravity.
  6. The lower left allows you to configure the core fillings around the lifters. The setting for 'Visibility' isn't applicable for Revit, but it's there since AutoCAD and Revit share the same definition. The 'dimension' controls if the core filling should be dimensioned or not. By adding a value to 'Length' you control how long the core filling should be. In Figure 15 above it's 600mm which means that it's 300mm on each side of the lifter. Last we have the 'Cores', which is the setting to control in which cores the lifters should be inserted in.


The last tab in the definition contains information about naming conventions and filtering options.

  1. Group - a definition can be included in a group which makes it easy to filter out the beams later on e.g. the IMPACT Production applications. An example could be that we have two definitions for a hollow core slab that is 185mm thick. The difference is the cast-in material used for the lifts. This may not be important for the people in the production, but they just want to know if these two slabs are in the group 180-200mm or 200-250mm. To solve this, we can use the group parameter. 
  2. Product - another filter parameter.
  3. Prefix designation - on the drawings, there is an option to add a so-called designation that contains a prefix and the element thickness in centimeters + element height in centimeters.
    Figure 21. Designation of the element.
  4. Prefix element mark - the naming of the elements. 
  5. Prefix drawing name - sometimes, the naming of the element and drawings are not the same. In those cases, we can use this parameter to control the prefix for drawings. 


Figure 22. Naming tab.

The last information that can be added to the naming tab is the 'Building Information Properties' (BIP). These are used to get better information from combined models.


Figure 23. Building Information Properties (BIP).


The hollow core slabs needs to be connected to each other, and the rest of the building to provide stability. To do this, recesses needs to be added to allow these connections. In the 'Recess' tab you can predefine recesses that goes through the whole element to make it easy and efficient to add these recesses to the elements. 


Figure 24. Recess tab.

  1. Type - right now there is only one type available, along with 'None'.
  2. E - Diameter of the top recesses
  3. F - Diameter of the recess that goes through the element from left to right.
  4. Cores - setting to control in which cores the top recesses should be inserted in.
  5. Dimension type - there are three options:
    1. Centre
    2. X-axis only
    3. None

Recess Edge

The 'Recess Edge' is almost the same as the 'Recess' above, but this one will only add recesses to one edge of the element, where the 'Recess' adds a recess that goes through the element. 


Figure 25. Recess edge tab.

  1. Type - there are four options available:
    1. None
    2. Rectangular - one rectangular recess in the edge of the slab.
      Lägg till bild efter 133710
    3. Rectangular and circular - one rectangular recess in the edge of the slab, and a circular recess in the top of the second core.
      Lägg till bild efter 133710
    4. Rectangular and rectangular - one rectangular recess in the edge of the slab, and a rectangular recess in the top of the slab connecting with the first recess so that it shapes like a 'hammer'.
      Lägg till bild efter 133710
  2. A - Depth of the rectangular recess in the edge of the element.
  3. B - Width of the rectangular recess in the edge of the element.
  4. C - Length of the rectangular recess in the edge of the element.
  5. D - Depth of the recess going from core 1 to core 2. The height of that recess will be A-D.
  6. E - Width of the top rectangular recess. 
  7. F - Length of the top rectangular recess. 

Weep Holes

Since there are cores in the slabs, there is a risk of water collecting in the cores, and freezing in the winter. To prevent this, weep holes are drilled in the slab to allow the water to escape. 

weep hole.png

Figure 26. Weep holes. 

There are different weep holes that can be configured.

  1. Edge - weep holes added according to the short side of the slab. 
    1. Type - there are seven options available.
      1. None.
      2. Circular top - circular recess in the top of the slab.
      3. Circular bottom - circular recess in the bottom of the slab.
      4. Circular hole - circular recess that goes through the slab thickness.
      5. Rectangular top - circular recess in the top of the slab.
      6. Rectangular bottom - circular recess in the bottom of the slab.
      7. Rectangular hole - circular recess that goes through the slab thickness.
    2. Size - diameter/width of the recess. 
    3. Offset (A) - distance from the short side to center of the recesses. 
    4. Min length (B) - the minimum length of the slab where the second row of recesses will be inserted. 
  2. Recess - how weep holes should be inserted around recesses. 
    1. Type - same as for 'Edge'.
    2. Size - same as for 'Edge'.
    3. Offset (A) - distance from recess to where the weep holes should be placed. 
    4. Min distance to edge (B) - minimum distance between the short side of the slab and the recess. If it exceed the min distance, another recess should be inserted between the short side and the recess. 
    5. Type at edge - same as for 'Type'.
    6. Size at edge - same as for 'Size'.
    7. Offset at edge (C) - distance from the recess. 
  3. Core filling - how weep holes should be inserted around core fillings. The configuration is exactly the same as for 'Recess'.
  4. Min distance between weep holes - The three configurations above will work together. This setting defines the minimum spacing between weep holes in the element. 

Next: Draw hollow cores