Create Long Span Roof Trusses with Long Span

Video Transcript:

 Welcome! In this video, we’ll walk through creating a long span truss and discuss a few design considerations specific to shipping and manufacturing these components. Let’s get started!

Start by opening the component creation panel. Here we will set the length to 64 feet. Next we’ll add a 32 foot profile line. And we will set the slope to be six twelve.

Now Click Add Line.

To close this component out we can Click the close profile option 2 times and move on to the shape details.

For this demo we want the bottom chord to run through the heel so make sure those checkboxes are selected. And then click next.

In the Structural Details sections navigate to the bottom of this panel and access the Load Settings. Typically, these long span trusses are not used in residential settings so we will make sure “One-or-two family dwelling” is deselected.

Next, make sure “Sprinkler Installation Load” is selected and click the “Apply along Bottom Chord” checkbox.

Now click ‘Change the Settings for this Component’ to wrap up our changes to the Load Settings. Open the Analysis Settings and navigate to the “Other Settings” section. For this scenario we are going to say the structure has multiple of the same truss so we will select “Use repetitive Member Increase” and click “Change Settings for this Component.” Now we can insert the truss.

Let’s analyze the truss and see if any checks are over capacity. Select Analyze from the menu to run the check. For all  trusses we want to make sure each connection is where we want them to be.

The analysis shows some checks are exceeded. We can see some of our plates on the bottom chords don’t have enough grip. Hover over one to show this data.

 Let's select the bottom chords and upgrade them to be 2x6. Next we will right click, then select edit lumber, here we will select 2x6 from the list. To see these changes take place we need to re-analyze the truss. After the truss has been re-analyzed, we can see that this solved our issues at the splices, but we still show that the heels are exceeding capacity.

We could upgrade the top chords to be 2x6 and that would solve the load issue. But that would increase both cost and overall weight.

A better solution is to add sliders to the corners of the bottom chord.

Click edit truss from the actions toolbar. Then click adjust heels. Here we can set the Left heel reinforcement to top chord slider. And we can do the same for the right heel reinforcement. We will leave the other properties set as they are. Click close.

We will now re-analyze the truss with the sliders added.

Looks like this worked. Let's zoom in to one of the plates at the heel. We should see no issues with the plates, now that we added these additional sliders.

Now we know this truss will work for the given situation, but certain details must be considered when designing a truss this size. Many manufacturers do not have the ability to fabricate this truss, let alone ship it. Shipping limitations vary, so be sure to check your regional requirements. Given this information we would likely design a piggyback truss to allow shipping and on site assembly. We will cover piggyback trusses in a separate video.

Thanks for watching !