engineering Archives

Truss Tuesday: Will it Bend?

by Seth Duncan | Apr 30, 2024 | Educational, Truss Tuesday

This week’s truss:

Question: Which member of this hip girder has the highest stress? There are jacks every 2 feet across most of the bottom chord.

Building Code: FBC2020

Loads (psf unless otherwise noted):
TC Live Load 20
TC Dead Load 10
BC Live Load 0
BC Dead Load 10

Wind: 160 mph

The answer will be posted on Thursday!

This is not a production truss! This is simply an example for Truss Tuesday conversation.

Updated Thursday, May 2nd 2024

Answer: The highest stress occurs at the vault in member B3. The lumber grade would have to be upgraded to Dense Select Structural to handle the bending.

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Truss Tuesday: Coffee Shop Conundrum

by Seth Duncan | Mar 19, 2024 | Truss Tuesday

This week’s truss: Vaulted Variance

Question:

Joe is opening his own coffee shop and he wants to have a vaulted space with nice light fixtures hanging from the ceiling. How would you upgrade this truss to given that information?

Top Chords are Number 2 Southern Pine
Bottom Chords are Select Structural
Webs are Number 3 Southern Pine

Building Code: IBC 2021

Loads (psf unless otherwise noted):
TC Live Load 20
TC Dead Load 10
BC Live Load 0
BC Dead Load 10

Application: Commercial
Wind: 110MPH

The truss has been designed for a 250LB moving load anywhere along the bottom chords.

The answer will be posted on Thursday!

This is not a production truss! This is simply an example for Truss Tuesday conversation. Join the conversation on LinkedIn.

Updated: Thursday, March 21st.

Answer:

You could do this in many ways, but one solution would be to upgrade the top chords to Number 1 Southern Pine and the Webs to Number 2 Southern Pine.

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Truss Tuesday: Flat Roof Optimization

by Seth Duncan | Mar 14, 2024 | Truss Tuesday

This week’s truss: Flat Roof Optimization

Question:

What would you do to make this truss design more efficient?

Top Chords: 2×4 Southern Pine #2
Bottom Chords: 2×4 Southern Pine #1 or Select Structural (B4, B5)
Webs are 2×4 Southern Pine #3 or #2 (W2, W20)
Building Code: CBC 2022

Loads (psf unless otherwise noted):
TC Live Load 20
TC Dead Load 20
BC Live Load 0
BC Dead Load 10

Wind: 160 mph

Carried trusses with net reactions of 100 lbs downward at 13’10 and 26’

The answer will be posted on Thursday!

This is not a production truss! This is simply an example for Truss Tuesday conversation. Join the conversation on LinkedIn.

Updated: Thursday, March 14th, 2024

Answer:

Here are the first things we would change:

Offset the splices. Lining them up like this creates weak points in the chords
Position a vertical underneath each point load

The results:

No more Select Structural in the bottom chords
Total plate area reduced by 25%

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Truss Tuesday: The Pool Table Problem

by Seth Duncan | Mar 5, 2024 | Truss Tuesday

This week’s truss: Pool Table Problem

Question:

You’re building a house and have plans for an amazing man-cave that includes a pool table. Will the trusses you have designed support the 1000lb table?

All lumber is Southern Pine MSR 2400 F 2 0 E

Building Code: IBC 2021

Loads(psf unless otherwise noted):
TC Live Load 20
TC Dead Load 10
BC Live Load 5
BC Dead Load 10
Application: Residential

Wind: 115mph

The answer will be posted on Thursday!

This is not a production truss! This is simply an example for Truss Tuesday conversation. Join the conversation on LinkedIn.

Updated: Thursday, March 7th, 2024

Answer:

Unfortunately, you may need to reconsider your pool table material. A 1000lb pool table would put too much stress on plates 14 and 15 and potentially cause them to lose grip on B2.

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Truss Tuesday: Long Truss Span

by Seth Duncan | Feb 27, 2024 | Truss Tuesday

This week’s truss: Long Truss Span

Question:

What is the longest truss you’ve seen in the wild? Do you think this 65’ long agricultural truss would work in a pole barn?

Top and Bottom Chords are 2×6 Southern Pine #2
Webs are 2×4 Southern Pine #3

Building Code: IBC 2021

Loads(psf unless otherwise noted):
TC Live Load 20
TC Dead Load 10
BC Live Load 0
BC Dead Load 5

Application: Agricultural

Wind: 110 MPH

Terrain Exposure Category: C (Scattered Obstructions)

The answer will be posted on Thursday! This is not a production truss! This is simply an example for Truss Tuesday conversation. Join the conversation on LinkedIn.

Updated Thursday, February 29th 2024

Answer: Yes! This truss will work in this situation; however, most component manufacturers would split this into two separate trusses to make shipping easier.

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