hip beam design
hip beam design
(OP)
I have a silly question that goes back to statics.
A simple span roof hip beam's load is a distributed load of triangular shape with load "0" at the corner of the roof and max. at ridge connection. I get confused over the tributary area.
Assuming 34 psf dead and live load, and assuming that the hip is the diagonal of a 9ft X 9ft square (18ft wide roof with equal slopes) and assuming I'm using the true length of the beam -as supposed to the projected length-
What is the load configuration? What is the height of the foot of the triangular load at ridge connection?
Anybody that might help please enlighten me.
PS. I could do this with any of the programs for wood but I believe that one should do this by hand until he or she is completely confortable with it before using any software..
A simple span roof hip beam's load is a distributed load of triangular shape with load "0" at the corner of the roof and max. at ridge connection. I get confused over the tributary area.
Assuming 34 psf dead and live load, and assuming that the hip is the diagonal of a 9ft X 9ft square (18ft wide roof with equal slopes) and assuming I'm using the true length of the beam -as supposed to the projected length-
What is the load configuration? What is the height of the foot of the triangular load at ridge connection?
Anybody that might help please enlighten me.
PS. I could do this with any of the programs for wood but I believe that one should do this by hand until he or she is completely confortable with it before using any software..






RE: hip beam design
The load would be (approximately) 9' times 34 psf. 4.5' of load comes from one sloped section of roof, and 4.5' comes from the other sloped section of roof.
Now, I said approximately, because the dead load portion of the total load would be a little more, because the span of the sloped section of the roof is a little more than 9', because it is sloped. But snow load is a projected load, so the 9' is exact for that.
DaveAtkins
RE: hip beam design
really want to do it right then you need to have live load and dead load perpendicular and parallel to your member (for moment and axial), then you use true length, then use the unity equation. But thats just too complicated especially because the deflection controls most of the time on timber.
http://www.swijetty.com
Sea Water Intake and Jetty Construction
RE: hip beam design
My answer would be the max load on the hip beam is 6.36' x 34psf.
My reasoning: Lets say the 9'x9' section of roof has a 12.73' diagonal (the horizontal span of our hip beam).
All rafters in the roof are supported by one of the 9' walls on one end and the Hip on the other end.
We can say half of this 9'x9' roof area is supported by the hip beam, the other half by the two walls.
The triangular tributary area on one 9' wall would be 0 at the corner to 4.5 ft at 9'. (1/2 x 4.5' x 9' = 20.25 sf)
Since the hip carries the same load as each wall, the triangular load on the hip won't be 0 at the corner and 4.5 at the max because 1/2 x 4.5' x 12.73' = 28.64 sf > 20.25 sf.
To get the same square footage, the correct max load per side of the hip is 9'/12.73' x 4.5'=3.184 ft at the ridge
1/2 x 3.182' x 12.73' = 20.25 sq ft.
That gives 3.182' x 2 sides = 6.36' in this case.
Of course, the other answers will work, but this way can help you sharpen your pencil if you start to get huge beam sizes.
RE: hip beam design
RE: hip beam design
DaveAtkins
RE: hip beam design
I still see mostly stick framed roof on all of the high end homes we are doing. They really want to have that high pitch ceiling and they would not want to settle with scissor trusses.
http://www.swijetty.com
Sea Water Intake and Jetty Construction