Samwise Gamgee
Structural
Has anyone done foundation design for pre engineering metal buildings? Please reference any useful resources or design examples.
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Foundation Design for Pre Engineering Metal Building 6
- Thread starter Samwise Gamgee
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Guest090822
Structural
I have - it depends on the type of building. Can you post a sketch?
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- #3
Samwise Gamgee
Structural
It's a simple treatment plant 40x50 feet. I am having my drafter put together a preliminary sketch . I can share the sketch once its available.
I just wanted to rundown all the things I need to be considering while designing this
[ul]
[li] Design for gravity loads at columns/wherever steel connects to the foundations [/li]
[li] Design foundations for lateral loads (Wind/Seismic) [/li]
[li] Should I design a mat foundation with SOG or just a thin SOG with isolated footings ? [/li]
[li] Any other other special criteria that I need to be aware of ? [/li]
[/ul]
I just wanted to rundown all the things I need to be considering while designing this
[ul]
[li] Design for gravity loads at columns/wherever steel connects to the foundations [/li]
[li] Design foundations for lateral loads (Wind/Seismic) [/li]
[li] Should I design a mat foundation with SOG or just a thin SOG with isolated footings ? [/li]
[li] Any other other special criteria that I need to be aware of ? [/li]
[/ul]
Soil conditions come to mind.
Wind and seismic loads can have uplift components.
The type of foundation depends on the magnitude of all the loads plus the soil bearing capacity at a given footing depth. You aren't saying much. 1 story, 3 or 4/12 pitch, 40ft clear span, seismic zone, hurricane winds, trolley loads???
Wind and seismic loads can have uplift components.
The type of foundation depends on the magnitude of all the loads plus the soil bearing capacity at a given footing depth. You aren't saying much. 1 story, 3 or 4/12 pitch, 40ft clear span, seismic zone, hurricane winds, trolley loads???
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- #6
Samwise Gamgee
Structural
Here is a sketch
The soil is pretty awful, I am still waiting to get some geotechnical information. I am a bit worried that if the soil capacity is bad, I might have to rely on piles. Is there are criteria which says if we are below a specific bearing capacity, we have to rely on Deep Foundations like Piles ?
The soil is pretty awful, I am still waiting to get some geotechnical information. I am a bit worried that if the soil capacity is bad, I might have to rely on piles. Is there are criteria which says if we are below a specific bearing capacity, we have to rely on Deep Foundations like Piles ?
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- #7
Foundation for PEMB is a bit unique. If I had to make a quick summary on the a few unique things would be:
Everything is dimensioned off of steel line and not off the column centerline
Uplift governs foundation design more often then bearing
Anchor bolt concrete breakout for shear and tension govern design a lot of times
Need to determine how you are going to address shear with hairpins, tie beams, moment footing, etc.
There is a bit more I cant think of off the top of my head. I would recommend the book "Foundation and Anchor Design Guide for Metal Building Systems" by Alexander Newma. He does a good job discussing PEMB foundation. This book was well worth the money for me.
Also is a link to a article that discusses PEMB foundation basics
Everything is dimensioned off of steel line and not off the column centerline
Uplift governs foundation design more often then bearing
Anchor bolt concrete breakout for shear and tension govern design a lot of times
Need to determine how you are going to address shear with hairpins, tie beams, moment footing, etc.
There is a bit more I cant think of off the top of my head. I would recommend the book "Foundation and Anchor Design Guide for Metal Building Systems" by Alexander Newma. He does a good job discussing PEMB foundation. This book was well worth the money for me.
Also is a link to a article that discusses PEMB foundation basics
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JoelTXCive
Civil/Environmental
I have just designed my first foundation for a PEMB. I relied heavily on Newman's book. It's very good and has design examples.
He has tables in the back of the book with preliminary loading values. I used those preliminary loads to generate my design details. I won't know the actual design loads until I get the sealed drawing back from the PEMB subcontractor.
Below are the preliminary loads for a 40ft single span building. Newman only has tables for a 1:12 roof pitch, and not 4:12; but it's a starting point.
I think Nucor Steel has preliminary loading values in one of their design books, but I couldn't locate it this evening.
I believe Newman assumes an 80mph base wind speed and an Exposure Factor of B or C
He has tables in the back of the book with preliminary loading values. I used those preliminary loads to generate my design details. I won't know the actual design loads until I get the sealed drawing back from the PEMB subcontractor.
Below are the preliminary loads for a 40ft single span building. Newman only has tables for a 1:12 roof pitch, and not 4:12; but it's a starting point.
I think Nucor Steel has preliminary loading values in one of their design books, but I couldn't locate it this evening.
I believe Newman assumes an 80mph base wind speed and an Exposure Factor of B or C
- Thread starter
- #11
Samwise Gamgee
Structural
Can someone explain the concept of gale rigid frames exerting horizontal column reactions on the foundations in the same direction ? How do I calculate these values ?
If you can picture a simple beam with a loading on it, the ends of the beam want to rotate. This rotation is transferred to the supporting 'legs' of the rigid frame. The rotation wants to force the bottom ot the legs outwards. A horizontal reaction is required to 'force' the bottom of the legs back into their original position.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
Cut a metal coat hanger and bend it to look like your frame.
Squash it a little like your load does and both leg bases will move outward.
You will have to push the bases back into place with your fingers applying forces similar to the red arrows in your diagram.
Squash it a little like your load does and both leg bases will move outward.
You will have to push the bases back into place with your fingers applying forces similar to the red arrows in your diagram.
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- #15
Samwise Gamgee
Structural
Thanks for the example , they make it very clear. So if I have to hand calculate those forces , how do I do that ? If I consider moment about any random point, the moments due to the horizontal forces will always be zero , so I am clueless as to how to calculate those horizontal forces ?
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- #17
Samwise Gamgee
Structural
I was worried that was the case, brings me back memories from Grad school. I am too lazy to hand calculate them, so I just used SAP
I think most engineers would do the same... maybe a different software program... it's nice to have the 'old way of doing it' in your pocket in case you don't have access to the equipment.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
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1
- #19
The copper wire "analog" model works especially well as an aid to understanding how best to handle stresses of unusual pipe configurations. I used to keep a length of copper wire on my desk.
Gaudi designed the Sacred Family Cathedral in Barcelona for compressive loads using an inverted tension model of the structure made with strings with appropriately sized sand bags located at all steples and arch intersections. The model still hangs in his design workshop in the basement. Add sand until all bags hang straight down. Multiply all forces by -1.
When do you suppose that method was first used? Looks like something from Galileo's days.
Gaudi designed the Sacred Family Cathedral in Barcelona for compressive loads using an inverted tension model of the structure made with strings with appropriately sized sand bags located at all steples and arch intersections. The model still hangs in his design workshop in the basement. Add sand until all bags hang straight down. Multiply all forces by -1.
When do you suppose that method was first used? Looks like something from Galileo's days.
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