Since it's an existing structure, you really don't need to have a parametric truss. I'm assuming that the majority of trusses are identical. I would just use static, non-parametric geometry. Do you have a CAD file you can import to Revit and use to trace? This would be the easiest thing to do. Then you can just pick lines. Step by step if you have a CAD background. 1. Start with a new family file - structural framing - trusses and complex. 2. Under Settings -> Family Categories and Parameters -> [Check: Work Plane Based, Uncheck: Always Vertical] 3. Insert your CAD background into a default Left or Right view. Position the CAD sketch so that the middle a bearing point - it can be the high or low bearing point - is at the predefined crosshair. 3A. In regards to step 3: You may also be able to, and this would be the preferred method, position the crosshairs on the CAD drawing. For the preferred method you will want to insert the CAD drawing at origin to origin, and move the crosshairs in the Left/Right views as necesary. 4. Use your CAD background to pick lines - Symbolic Lines -> Structural Projection. I would pick the top of the top chord, the bottom of the bottom chord, and the bottom of the extensions. You'll also need to pick the centerline of the webs. This is easiest to accomplish using the offset command in AutoCAD prior to building the truss. 5. Trace your masonry walls with Reference Planes. It doesn't need to be detailed - just the top of wall, inside and outside faces. You'll need these to create your bearing plates while in plan view. 6. Load the families you need to use. There are two ways of accomplishing this. You can load actual 3D modeling elements such as the W-Beam family, or you can load the individual 2D profiles. Revit will still try and snap certain framing members together, so it may be easiest to just load the 2D profiles and create sweeps with them. 7. Begin creating sweeps, but turn your CAD background off first, and cut a section at the midpoint of your sweep paths. This section will allow you to adjust the position of your 2D profiles relative to the path centerline. Use the 'Pick Path' option and select the symbolic lines you just created. For editing the sketch, choose the 2D profiles you just loaded into the project. 8. Use a single sweep for the webs. They appear to be bar-joists. 9. Depending on how your bearing plates are constructed, you can either use a double angle profile for a sweep, or you can create extrusions in plan. This is where you'll be using the reference planes you traced the masonry walls with. 10. Visibility - Everything in your family has a visibility setting, I believe that includes the CAD drawing as well (which you should erase when you are done using it). See step 3 and 3A. If you insert the CAD drawing at origin to origin, it will be easier to modify the family if you left something out. You can always insert at origin to origin and know that the drawing is placed in the same location as the first time you created the family. But, back to visibility. Everything in your family has a visibility setting- including lines and geometry. You'll want your lines to be visible in course views, and your geometry to be visible in medium and fine views. You can adjust the visibility of each element through the 'Visibility' button on the editing bar. You can edit visibility of elements on an individual basis, or with multiple elements selected. 11. After you've adjusted visibility paramaters, load the truss in your project. 12. In your project, you'll want to create a reference plane or datum plane you can associate your truss to. You'll have to rename the reference plane if you decide to use a reference plane. Also, I pin any reference planes I rename, since they're easy to unkowingly erase. Now, if you erase a pinned reference plane, Revit will warn you that pinned objects are being deleted. 13. Choose to create a beam, and select your new truss from the type selector- which by default should be the truss you just loaded into the project. When you are placing the reference plane, you will receive a 'not allowed' icon for your cursor. From the editing bar choose to place by work plane, and select the reference or datum plane you just created in step 12. That's pretty much all there is to it. You'll of course want to save the family, but you won't need family types. If you need to make a modification to the truss, I would just copy the one you've just created, do a save as, and modify as needed. Was that clear? How did you do?
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