Grading relationships provide detailed control of elevation relationships between Allsite objects. An example may be where a split building pad with walkout basement is required, in this case the 2x building pads have a 'fixed' relationship between them.
You can add a grading relationship between the following objects:
Building
Road corridor extent
Road centerline
Road centerpoint
Road modifier (ie curb)
There are different relationship types, up to 3x relationship types can be added to any relationship:
Fixed - used in isolation where there is a fixed elevation relationship between 2x items
Minimum - the minimum allowed elevation between the 2x items
Maximum - the maximum allowed elevation between 2x items
Fixed Or - used in conjunction with Min / Max relationships. An example of this is when defining a small step between 2x building pads, say a garage and the living area, it either needs to be flush (ie "Fixed" to 0ft offset) or at least 1 step (ie 8 inches).
If adding a vehicle crossing relationship on a vacant parcel, use the Vehicle crossing min/max relationship on a parcel, not a grading relationship.
Bulk adding relationships (buildings)
You can bulk add relationships between buildings, to do this follow the steps outlined below:
Building to Road Relationship
Select the buildings in the model you want to add relationships to
Add up to 2 relationship types
Run Level AI Prepare, this generates the relationships.
Adjust any relationships that are snapped in the incorrect direction (ie corner lots above where want the relationship to the other road)
Group edit the relationships to set the relationship types (up to 3) and the relationship elevation difference. This can be negative or positive depending on what sort of relationship is required. In the example below all 129 buildings are set to a 2ft offset from the curb
Building to Building Relationship
If defining a split pad you will need to ensure the surrounding ground (ie parcel / ground control) can grade with the relationships. To start, set the relationship on the building to "BUILDING".
After running prepare a relationship link is created, specify the offset. Next, add grade breaks / ground control with appropriate max heights to allow the ground to grade around the relationship. In the example below the 8 foot relationship between the pads would not work as the parcel max grade is set to 5% - this would cause a non viable design or potentially design 'run-away'.
Adding a grade break with maximum height set to 8ft resolves this. NOTE - The grade break needs to extent to the boundary otherwise the land next to building is also too constrained.
