Structural Engineering Question
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Fnaar
Smutmaster General
- Location
- Thumberland
Is it going to be a sex dungeon? (but in the roof) 
Beebo
Firm and Fruity
- Location
- Hexleybeef
If it's anything like my loft it will be suitcases and christmas decs.
Archie_tect
De Skieven Architek... aka Penfold + Horace
- Location
- Northumberland
+ goldfish tank, gerbil cage, old pram frame [to make super fast go-cart for grandchild], baby's cot [for grandchild].... sensing a theme?
Chris Norton
Well-Known Member
- Location
- Boston, Lincs
I'm curious about trusses that take UDLs. The UDLs can be converted to point loads at the nodes, and these point loads can be converted to compression and tension stresses in each chord (assuming pin joints, that is). However, in reality, each chord with a UDL also takes bending stresses. In the real world, do truss designers check all members for tension, compression and bending etc? I'm pretty sure that they do.
It's been a while since I had a need to dip into Ozelton and Baird! Thanks.
The roof truss designer really is little more than a computer entry geek now. The software used is so powerful you can literally enter the walls, the pitch of the roof on that wall, press a button and it will go away and design the whole shooting match. But as I'm old skool.........
UDL's cannot be converted in to point loads at nodes. They are different stresses placed upon the member's involved. For instance, imagine a hoist load for a disabilty hoist (not as per the OP). The load track may be perpendicular to the ceiling joist in which case a point load is applied or along the joist in which case a UDL live load is applied. Both will give different results in design.
The software does all the checks now, including snow drift and wind uplift (particularly relevent in Scotland) although truely accurate results do require you to put in the OS reference and altitude. It's all done with a blink of an eye.
If it was still the case where we worked it all out as per 20 years ago, roof's would no way be as complicated as they are now or would be so much more expensive due to the designers skill. I would not have finished my career at earning 27k a year it would have been more like 75k. New ones now may not earn much more than 11 to 12k. Yes it's that simple and I could do 15 roofs a day with miteks system, doing full roof layout drawings and producing all the required cutting details for the factory.
However, it didn't stop builders threatening to throw me off 3 storey scaffolds cos something was 40mm to short..............
mark st1
Plastic Manc
- Location
- Leafy Berkshire
subaqua
What’s the point
- Location
- Leytonstone
so a cock loft thenIs it going to be a sex dungeon? (but in the roof)
warm enough for no coat
Chris Norton
Well-Known Member
- Location
- Boston, Lincs
[QUOTE 2536193, member: 9609"]I would not have thought the strength of the truss would have been weakened, basically I have just altered the angle of the strut by a few degrees, and the bolted / metal plate will be stronger than the original plate. The other end of the strut has been properly mated into the king post / ridge beam connection. I did cut the ridge beam to make the loft hatch bigger - but I thing that is allowed? and I did form a proper nogging (?) between the two adjacent ridge beams to support the one I cut.
Good point about an over eager surveyor selling the house; if I ever come to sell it may be prudent to put it back the way it was.
So anyway, with that bit more info, any sort of ball park figure for what would be a safe max load and breaking point. I'm guessing, getting dodgy at half a ton, but would probably go up to a couple (would need something better than my old climbing rope).
I'm just curious, I doubt it will ever have more than 10 stone on it.[/quote]
Once the truss has been cut, unless an engineer does all the calculations, then it's just timber. Yes the bolted plate is probably mighty fine for the job.
So onto the weight you really want to know. No roof truss that I know would realistically take half a ton at a node point. I would consider it to be capable of taking 30 stone easy but I wouldn't push it much more.
As an aside, before I left the industry we were having to put spaces in bungalow roofs so that a family of four could use it as an escape in case of flooding.
Good point about an over eager surveyor selling the house; if I ever come to sell it may be prudent to put it back the way it was.
So anyway, with that bit more info, any sort of ball park figure for what would be a safe max load and breaking point. I'm guessing, getting dodgy at half a ton, but would probably go up to a couple (would need something better than my old climbing rope).
I'm just curious, I doubt it will ever have more than 10 stone on it.[/quote]
Once the truss has been cut, unless an engineer does all the calculations, then it's just timber. Yes the bolted plate is probably mighty fine for the job.
So onto the weight you really want to know. No roof truss that I know would realistically take half a ton at a node point. I would consider it to be capable of taking 30 stone easy but I wouldn't push it much more.
As an aside, before I left the industry we were having to put spaces in bungalow roofs so that a family of four could use it as an escape in case of flooding.
