Load Take Downs for Residential Structures

[medeek]

When I start a project I usually determine my vertical loads first.

I will manually calculate the roof loads, floor loads, dead weight wall loads etc... as they are applied to the rafters, trusses and floor joists and resolve these into the beams, headers, bearing walls and columns as appropriate. Usually my areas are quite small so live load reductions don't factor in. Also it is usually quite clear form the outset whether the snow or live roof load will govern so I can usually eliminate one or the other from my calcs to simplify things.

I've been thinking lately though it would be nice to have a software that could help with this process. Does such a product already exist? If not I think it might be interesting to invest some time and effort into programming such a product if others might find some utility in it.

My biggest concern with the manual method I currently employ is the possibility of calculation errors and not having a way of checking my numbers with some independent method. On occasion I have found myself forgetting to divide the reactions from a floor joist by the correct on center spacing which has either over engineered the affected beam or under sized it, obviously one more serious than the other.

A load take down software would be a useful checking tool in my opinion but I am wondering what others are currently doing or what their opinion is on the matter.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[msquared48]

Well, Woodworks does what you describe...

Mike McCann, PE, SE (WA)

 

[medeek]

I use Woodworks Shearwalls software for the lateral design but I'm not sure on the vertical. How does it know which way the floor joists run or if there is a beam in a certain spot?

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[msquared48]

You tell it what the structure is and it designs the members bade on the area loads you input.

Mike McCann, PE, SE (WA)

 

[medeek]

Which component of the Woodworks design software are you describing?

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

Okay, Woodworks Sizer... I did not realize this component had the concept mode I thought it was only for sizing beams etc... I'm going to have to play with this, thank-you for pointing this out.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

Seems pretty straight forward, however I am wondering what is the best way to model manuf. trusses within sizer.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[medeek]

Another thing I've noticed with the software is it does not appear to calculate the dead weight of walls or include this dead weight in any of the calculations automatically. Has anyone else noticed this behavior?

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[XR250]

I usually don't include interior wall dead weight unless it is a significant portion of the trib. area of the member. There is enough fat in the floor DL and LL to account for it. I typically don't design near minimum code either so I have more fat. I do design for exterior wall weight however.

 

[medeek]

I don't seem to get any weight for exterior walls in the software.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[XR250]

FWIW, I would still prefer to calc the loads myself instead of using the software. There is probably just as much chance for error using the software and you don't get as good as a "feel" for the structure. I could likely do it faster by hand as well. Seems that most of my time is spent figuring out the best load path to take, rather than doing the calcs.

 

[medeek]

I will keep with my manual calculations, but it would sometime be nice to have a sanity check using a different method.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com

 

[jayrod12]

In my experience a reasonable sanity check is 165 psf at the t/o foundation wall for a standard single storey with 30 psf snow and stucco exterior walls.

If my actual calcs are within 10% of that then I haven't made any glaring errors.

And then it's about 80-90 psf per floor including bearing walls.

At least that's how I do my quick sanity check.

The more open concept of the residence the more my plan breaks down. But that's the nature of open concept houses.

 

[manstrom]

I find it is easier to run them by hand than put it in a program.

If you want a sanity check, you could add up all the reactions and compare to total loading.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller