When modelling Structural objects such as walls, columns and trusses it is sometimes very useful to attach the top or bottom of these elements to other structural objects such as roofs, floor slabs and foundations etc. This technique will maintain a parametric relationship between the elements and accommodate edits such as slope and elevation.
You can attach the following families to the references in the table below:
We will start by looking at attaching structural columns to Floors.
Select a column and then click Attach Top/Base from the Context panel as shown below.
On the Options Bar below the Ribbon you will see the following
You can of course attach either the Top or the Bottom of the column to a floor slab, the attachment Justification allows for the following processing of the In Situ Concrete columns:
As you can see the in Situ Concrete members will join as expected but the Steel, Timber and Precast columns will prove more problematic. These columns will not cut and a Reference plane will need to be utilised to create the required detail.
If a Structural Column is attached to a non-structural target such as a roof or ceiling then you will see the following warning, the column is still attached but the analytical model will have no connectivity and behave like a mast!
Walls have a similar workflow where you can attach either the top or base of a wall to a roof, floor, ceiling or another vertical wall. The below image shows a simple example of attaching a block work wall to two structural slabs.
Things can get a little more challenging where you have a situation as shown below where your wall needs to attach to the underside of a beam. In this situation you will need to select the wall and then edit the profile and then use the pick lines tool to create the required geometry.
Also note that if you edit the profile of a wall then this will disassociate the constraints that the Attach Top/Base command adds.
Trusses can be attached to roofs and floors and enables the user to attach the top or bottom boom to various floor shapes. The below example shows a steel truss with the top chord attached to a sloping floor.
Here are some more examples with a timber truss attached to a roof and a steel truss attached to a roof that was created as an extrusion.
If the Top and Bottom chord are drastically different then you may have to make use of the Edit Profile tool on the contextual ribbon. This allows the user to create a sketch for both the top and the bottom chords. Also notice that once the truss has been created you can effectively ‘explode’ the truss to structural framing with the Remove Truss Family command.
Enjoy,
lawrenceH
Autodesk Revit Structure 