Structural Engineering Question
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subaqua
What’s the point
- Location
- Leytonstone
slowmotion
Quite dreadful
- Location
- lost somewhere
You need this book by Ozelton and Baird....
http://www.amazon.co.uk/Timber-Desi...76744&sr=8-1&keywords=Timber+Designers+Manual
I bought the first edition thirty years ago. It's a brilliantly well-written text book.
http://www.amazon.co.uk/Timber-Desi...76744&sr=8-1&keywords=Timber+Designers+Manual
I bought the first edition thirty years ago. It's a brilliantly well-written text book.
Archie_tect
De Skieven Architek... aka Penfold + Horace
- Location
- Northumberland
Reiver.... I haven't worked out the node point loading on fink or 'W' braced trusses for about 30 years, but I know a man who does! I might still have the calculation sheets n my architectural structures notes from 1979!
Chris Norton
Well-Known Member
- Location
- Boston, Lincs
Roof truss designer for 20 years.
One set of plates have been removed. Therefore the truss is effectively bollocksed. The bonus point is that sarking has been used. What's the connection of the piece of timber to the ceiling joist? You may be able to get away with a general cutting option for roof trap's. May need to brace back the ceiling joist to the adjoining trusses. No need to worry excessively from the thing collapsing. Your problem will be if/when you decide to sell the house and any competent surveyor will look at that and just go "hold on, that needs checking".
The worst example I ever saw was someone who cut the whole lot out and the roof was deflecting so badly that I popped my head through the hatch and refused to stay any longer in the house. Condemned the lot.
Right. to work out the load's I can tell you exactly what it has designed into it.
Node points of roof trusses have 450n designed at them. Short term load only, described as, funnily enough, the man load.
Want to get one tested? That will be 2 grand then sir plus the cost of the truss and delivery. Fascinating though to see them go. Generally the apex lets go first, at 4 to 5 times designed load. Quite impressive considering the small timber sections used. The design requirements we used were brought in generally for steel structures which let go far closer to design loadings than timber structures. No need for testing though. It's been done to death now and we know what we are talking to. Also, the snow load on a roof truss equates to approx 10ft of snow. Doubt that you get that on there too.
If you want to know more then (on experience they look like Mitek plates http://www.mii.com/unitedkingdom/ ) Contact them if you have any queries. The original designers are required to mark the truss so that they can go back to the job up to 15 years after it was produced and still get the details.
Can you send me a picture of the ceiling joist connection?
One set of plates have been removed. Therefore the truss is effectively bollocksed. The bonus point is that sarking has been used. What's the connection of the piece of timber to the ceiling joist? You may be able to get away with a general cutting option for roof trap's. May need to brace back the ceiling joist to the adjoining trusses. No need to worry excessively from the thing collapsing. Your problem will be if/when you decide to sell the house and any competent surveyor will look at that and just go "hold on, that needs checking".
The worst example I ever saw was someone who cut the whole lot out and the roof was deflecting so badly that I popped my head through the hatch and refused to stay any longer in the house. Condemned the lot.
Right. to work out the load's I can tell you exactly what it has designed into it.
Node points of roof trusses have 450n designed at them. Short term load only, described as, funnily enough, the man load.
Want to get one tested? That will be 2 grand then sir plus the cost of the truss and delivery. Fascinating though to see them go. Generally the apex lets go first, at 4 to 5 times designed load. Quite impressive considering the small timber sections used. The design requirements we used were brought in generally for steel structures which let go far closer to design loadings than timber structures. No need for testing though. It's been done to death now and we know what we are talking to. Also, the snow load on a roof truss equates to approx 10ft of snow. Doubt that you get that on there too.
If you want to know more then (on experience they look like Mitek plates http://www.mii.com/unitedkingdom/ ) Contact them if you have any queries. The original designers are required to mark the truss so that they can go back to the job up to 15 years after it was produced and still get the details.
Can you send me a picture of the ceiling joist connection?
Chris Norton
Well-Known Member
- Location
- Boston, Lincs
Yes, mostly felt here, but still see torching from time to time.
slowmotion
Quite dreadful
- Location
- lost somewhere
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
What do you want to know, are you asking for an OK that your hoist isn't going to cause the roof to collapse? Your original truss designer probably wouldn't want to know, they'd tell you that it isn't designed with a hoist load at that point and the removal of the nailplated web invalidates any warranty, as CN states the truss will have been designed with a man load, one of the issues you might get is if fully loaded the hoist dropped, it's the 'moment' when the load reaches the bottom that could cause damage. Anyway I've seen much much worse that hasn't fallen down, almost.
Oh yeah, and it's deffo a Mitek system roof.
Oh yeah, and it's deffo a Mitek system roof.
threebikesmcginty
Corn Fed Hick...
- Location
- ...on the slake
It's moved on from CP112 Archie, BS5268 came in a while ago now, if you hurry you could catch up before EC5 starts!
swansonj
Guru
[QUOTE 2520540, member: 9609"]How do you work out load bearing capacities ? For example how would I work out a safe working load for the following.
Note. before this thread turns into a long warning of stuff collapsing. I am aware the floor in a loft is not designed to be load bearing, and as such I don't have a great deal of weight up there. I have used this pulley for the past 10 years and I doubt I have had, or ever will have more than 8 stone on it. And it is clearly capable of a lot more than that - at a guess I would be comfortable with 30 or 40 stone.
So how would a structural engineer go about calculating max loads etc. I am presuming a figure could be worked out with out constructing another one then loading it until it breaks!
the wood is 70*35mm
[/quote]
That attic is a disgrace, there isn't nearly enough junk being stored in it.
Note. before this thread turns into a long warning of stuff collapsing. I am aware the floor in a loft is not designed to be load bearing, and as such I don't have a great deal of weight up there. I have used this pulley for the past 10 years and I doubt I have had, or ever will have more than 8 stone on it. And it is clearly capable of a lot more than that - at a guess I would be comfortable with 30 or 40 stone.
So how would a structural engineer go about calculating max loads etc. I am presuming a figure could be worked out with out constructing another one then loading it until it breaks!
the wood is 70*35mm
That attic is a disgrace, there isn't nearly enough junk being stored in it.
He's in between crops - see #5.
