18 Replies Latest reply on Sep 17, 2015 7:39 AM by Mark Greenwell

    Best method to model a truss

    Mark Greenwell

      Hi,

       

      What would be the preferred method to model a truss (see picture below), would you use weldments and the different section types and a master layout sketch, or build parts off a fixed part in as assembly?

       

      The bracing section as you can see only goes so far then it is welded to gusset plates on the UC section on the top & bottom boom.

      How would you get the bracing section to stop short of the intersection points.

      How would you model in the gussets and and how would I trim the section these around the gusset so there were bird mouth slots in the section to allow the gusset plates to slide into the section.

       

      Has anyone got any examples they could share with this type of frame.

       

       

      Thanks

       

      Mark (SolidWorks 2015 sp4)

        • Re: Best method to model a truss
          Deepak Gupta

          I would do that in weldment.

           

          You can split the sketch on top and bottom to define the stop of member. And change the small lines on both ends to constructions lines. Of course use dimensions to control the stop length.

           

          For gusset I would add a straight line and then using a weldment profile of the plate, I would create them. Add the chamfer and then use indent feature to create the cut with required clearance.

            • Re: Best method to model a truss
              Mark Greenwell

              Hi All,

               

              I have attached a very quick effort (1st time) at this.

               

              I have used weldment profiles for the section after splitting the lines.

               

              I then used an extruded sketch to get rough shape of the gussets and added a chamfer.

              At some point if I have a few to do then I will look at creating structural plate shapes.

               

              However at the moment I am just trying to figure out easiest way to do this.

               

              Then I used Indent to cut the hollow section where the gussets fit.

               

              I then went to save and the only option was to save as a part. Why not assembly?

               

              What is the best way to save out these individual pieces so you could make component sketches.

               

              Anyway attached is my 1st go at something like this so any feed back on what I am doing wrong is welcome (don't be too mean).

               

              The feature tree marker has been moved up before saving.

               

              Thanks

               

              Mark

            • Re: Best method to model a truss
              Glenn Schroeder

              I agree with everything Deepak said.  I'd definitely do that as a weldment, and also use the Structural Member function to model the plates.  (See Using Plate in Weldments for more information on that.)  I did want to point out that if the braces are hollow sections then I'm not sure the Indent feature will work properly for the notches.  You will likely need to use a simple Extruded Cut for those.

                • Re: Best method to model a truss
                  Matt Peneguy

                  The gussets gave me trouble and this may not be a trivial thing to do.  I have put a similar truss to my VAR about how to do this type of model because in my case we have to deal with camber of the truss due to dead load deflection.  We could not come up with a good solution. It came down to the fact that we had a 3d truss where the gussets would actually have to bend a little to meet up with the members, If it were just a couple of connections I could have manually defined the gussets, but I was dealing with a couple hundred connections...

                   

                  If your truss is "flat" and you don't have to deal with camber, then I think Deepak's and Glenn's solutions should work. 

                   

                  Though, I'll give you my two cents... From my experience, for the members, I would make a construction sketch of the skeleton where the center lines are shown (because they intersect, and that makes things easy).  Then I would overlay lines on the centerlines and dimension from the ends of the actual line to the center line or from the edge of the gusset, whichever is controlling in your case.  I've found that method to be the easiest to fully define the skeleton that will be the basis of the weldment with respect to the constraints of the structural guys. And if you want to get fancy, you could tie that dimension to a global variable... And if your structural requirements change (say you want to add a little length to the connections for extra strength) all you have to do is update that variable and voila all of your connections change...

                   

                  And I agree weldments is the right tool for this job.  No other method I explored even came close in terms of ease of use and time savings.

                   

                  Let us know how it turns out, and I am interested if you have any tips for me... Because like I said above, we have not found a good solution to my problem.

                • Re: Best method to model a truss
                  Elmar Klammer

                  You can try this.

                   

                  Use weldment for your structural members. Add the weldment into an assembly. Then add your plates etc. as parts. Make a assembly drawing and add a BOM (indented with cutlist info) to show all your properties. Have done this before works great. Just add a centroid point (x, y) for unsymmetric profiles like angles into your profile sketch so you can put the member profile center with you skeleton sketch (grab info from AISC shapes database or book). To trim you members either use a cut feature, move face, trim to surface or split your sketch (no need to convert to construction line - but you can if you want to.) If you use camber then you would most certainly model the camber into your skeleton sketch. That should give you what you need. Add the member properties into your cutlist folder (at part level) - Descriptions should be in your profile sketch. Other items like mark numbers you add manually.

                  Note: Drawings for weldments don't update the same as parts drawings. Often you loose dimensions attached to body after design change. No way around it, just deal with it. Pulling weldment body information into the title block needs a creative workaround. Make a title block as a drawing block and insert attached to member view. Then you can pull body information. All in all, this requires a fair amount of experience to do and to work reliably. It's simple if you know how, it's challenging if you don't.

                   

                  Hope that helps.

                   

                  Elmar

                    • Re: Best method to model a truss
                      Mark Greenwell

                      Hi All,

                       

                      Thanks for all the tips etc on doing weldments. I don't think I can give anyone the correct answer as everyone has contributed.

                       

                      I haven't decided which is my preferred option as after messing about with it yesterday I can see benefits of doing every thing in a weldment.

                       

                      I also like Elmar's suggestion of only doing the section etc in weldments then moving over to an assembly you do the plates.

                       

                      I will mess around a bit more.

                       

                      Screen shot of something I started yesterday to see what was the preferred option.

                       

                      What is the quick way to have the part custom properties populate the cut list part custom properties, I take it I don't have to keep adding every time I use a different section size.

                       

                       

                      Thanks

                       

                      Mark

                        • Re: Best method to model a truss
                          Deepak Gupta

                          What is the quick way to have the part custom properties populate the cut list part custom properties, I take it I don't have to keep adding every time I use a different section size.

                           

                           

                          Put the required properties once in your weldment profiles and you're good then.

                            • Re: Best method to model a truss
                              Mark Greenwell

                              Hi Deepak,

                               

                              That is what I started to do, by opening up the Library  feature section sketch and adding my custom properties then saving.

                               

                              But then I thought that there are hundreds of different profiles and I need to add quiet a few custom properties so this would takes me some time to do.

                               

                              I thought that there may have been a way to do it once and then every time a section size is used the custom properties would be automatically be added.

                               

                              Thanks

                               

                              Mark