Revit - Bridge part 4 - example 31

0. Intro

In this tutorial, bridge part 4, I will create a simple straight superstructure for a bridge in concrete using Revit, only. The superstructure will be created in a family template(Metric Generic Model) and will be parametric.

Parametric design
A parametric design is an object that is guided by a set of parameters. The parameters can be different kinds of values like numbers, rules, formulas, and relationships between them, and they control the design of the object. For example, in Revit, it can be a window that is controlled by a set of parameters. And if you change the value of a parameter, the window will change its design(If of course the parameters is set up correctly) 

Even if this is a parametric cross-section for a bridge, the principles used can be translated to other families, like door, window, chair. etc.

Bridge part 4 content:
-Superstructure created in Revit using a family template
– Parametric design
– Creating formulas for some of our dimensions 
– IF statement
– Weak, strong and not reference 
– Difference between type and instance parameter

Picture 0

1. Setting up Ref planes (RP)

Open up the family template Metric Generic Model, go to front view, here the cross-section for our bridge will be created.  Starting with is to set up all our Ref-planes,  the ref planes will work as the skeleton for the bridge cross-section and will constrain our element. 

Strong, weak, and not a reference plane
A strong reference plane is higher up in the hierarchy when it comes to snapping and dimensioning, if you have a strong and a weak ref plane close together, it will first snap to the strong one.

Another difference is when aligning, if you try using the aline tool on a weak reference plane in a family, the family will move to the aligned line, if the same task is done on a strong reference plane, the line will move to the family.

A not reference plane is not visible at all in the project and cannot be snapped or create a dimension between two not reference planes, really useful if you have a lot of reference planes that you know you won’t use when creating dimensions lines. 

Picture 1

2. Drawing lines

At this point, it looks a bit chaotic with all the ref planes, but that will change as soon as our lines are drawn up. (see picture below)

Create – extrusion-line
Then draw up a bridge cross-section, be aware that our line must snap to the ref-planes placed in section 1. 

Picture 4

3. Setting up dimensions(DI)

Next up is placing the dimensions, these dimensions are going to be paremtrcided(if that is even a word) in the next step. 

Picture 5

5. Creating the parametric values

This is the fun part! The parametric values we are about to create are the brain of the family, they control how the design will be.

Select a dimension and press create a parameter, the window(picture 6) will appear, we want this parameter to be an instance parameter. 

Instance vs type parameter

An instance parameter enables you to modify the parameter value separately for every instance, this means you can change a specific parameter in another instance of a family without affecting the original family. For example, you can have 3 different windows with different parameters value, they exist independent of each other. 

Can be edited in the properties box for the specific family. 

A type parameter enables you to modify the parameter value, which applies to all elements of the family type. This means if you have a window, and placed like 20 windows of that type in a building, you can change all the windows by just adjusting the parameter for one of them.

The parameters can be edited in the type properties menu.


Picture 6

5. Creating formulas

On the more advanced side, the use of formulas can be great and powerful to calculate values and control parametric content in a model, and also restrain and limit what other users can do(create a SafetyNet so other users don’t fuck it up!) 

In the formula column, you can use multiplication, subtraction, addition, division, sin, cos, roundup, round down and even conditional expression like IF statement, you will never feel as cool as when you implement an IF statement into your family. The possibility of creating a formula is a lot.  

The formula I have put in can be seen below. 

Picture 7

6. Upload into Revit

Before uploading, don’t forget to add a parameter for length(as seen in the video) save the family and press load into the project, and place the parametric bridge wherever you want. 

Picture 7