Ah, right, that's cleared that up then. ???????? :-(
If I go to my local builders merchant and ask for three, six meter long, 75mm by 225mm tannelised joists,will he know what I mean without my having to know what SC4, SS or C24 is all about?
Tim (who's getting more confused by the minute)
But Tim only has about 5 sq m, which would be Stefek and a bag of gravel. And a bridge over a burn is likely to have people crowded together playing poohsticks, or even jumping up and down. I think NP's proper solution might be needed.
Have you ever stood on a 9"x3" joist spanning 6m? Ever jumped up and down on one? Ever hung an engine hoist from one and hung a small block v8 from the hoist?
A fully triangulated bridge is lovely, but totally unnecessary in this case. Two 9"x3"s would be plenty, three would be what I'd use.
Nope, and I did think 250kg a bit low. How many Stefeks to a small block V8 ?
Better or cheaper than 2 substantial steel I beams?
With all the accessories, about 2.5 Stefeks.
Certainly cheaper, but also easier to source, prettier and easier to construct (how do you fancy drilling dozens of holes for the cross-members? Or carrying the steel beams?).
if you are going for this long span you will want a good graded wood,
these grades are based on various factors, and can be either visually (given BS4978) or machine graded (given BS EN 519). You can generally tell the grade just by looking at the wood (which is what the QP doing the grading does) going on the total knot content, their size and their distribution. Splits in the wood can count against the strength of a plank, a split along the grain does not count much against its overall strength, whereas a split traversing the width (partially or totally) will count considerably against. Machine grading is carried out by measuring the deflection of the wood versus weight applied.
Aldo grades should be based on the woods final usage e.g. wood for internal use should be graded as KD (kiln dried) or dry, and external wood as wet. Wood should be graded at the right moisture content for its intended purpose. however tanalised wood will be graded prior to tanalisation and will be very wet if sold shortly after being treated.
I am quite amazed sometimes though at what does actually get graded, and on quite a few occasions major faults in the timebers of 2x4 size can be shaken and snap quite easily
Ungraded (totally different from unsorted) can mean one of several things,
I genuninely hasn't been looked at and can be very good wood indeed.
however it now normally means that the person qualified for grading wouldn't want his personal stamp on that wood, as it really isn;t up to scratch.
Also something to look out for especially on 6m+ lengths of 9x3 or above is that it hasn;t been finger jointed (very fine teeth at about
5mm repeats and teeth depth of about 1cm) these can come in fully graded lengths, but i would err on the side of caution here if the wood is going to get wet and get wet often. I have seen these joints highly compromised if left in water for extended periods of time.....YMMVi hope that this will answer your question a little bit more fully
I thought it was 30 meter span actually. If it was 6m, then of course, its a snap. Ive got 7x3 spanning that sort of gap no problem
But IS it only 6M? I have no real way to go back to OP, I m sure I saw 30m.
That would *definitely* require a well engineered structure (or some really big tree trunks).
Exactly! That's what I've been saying. It really isn't that big a span, and using 3off 9"x3"s would give a very sturdy bridge with next to no deflection with a couple of people standing on it.
I am sure the OP said 30m. ooh. 19'. Mm. I read that s 19 meters, or about 60'.
OOPS :-(
1kg = 9.81N (OK I know you shouldn't equate force and weight) 1kg = 2.2lbs 1m2 = 10.76ft2
So 0.25kN=250N=25.48kg=56lbs/m2=5.2lb/ft2
The normally assumed live load on a domestic floor is 1.5kN/2 or about 30lb/ft2
In message , David Hemmings writes
That may be true in engineering and architectural circles. But at grass roots level it is alive and well. Hasn't quite filtered down here yet.
The building regulations own tables stipulate SC4 and SC3 as do many of the books.
I was quoting form tables found at the Office of the Deputy Prime minister and from the book "Building regulations in brief" by Ray Tricker and published in 2003.
For all practical purposes, yes. The C24 (C=coniferous=softwood D=deciduous=hardwood) is the Eurocode replacement classification for SC4 and defines the working stresses that can be used.
The GS/SS grading relates to the quality of timber (knots, slope of grain etc), and its strength will depend on its species. As it happens all the structural timber we use (i.e. northern European or North American) that is graded GS or SS falls into C16 or C24 but UK grown timber (IIRC) would fall into C14 or C22 - warmer climate = faster growing and less dense.
quite just as i posted yesterday
and its strength will depend on its species. As
Yes true, personally never seen wood stamped up like this. The market is totally saturated with the north european redwood, why ? easy it is better and cheaper than home grown. If you can get swedish over latvian then do so, it comes up much nicer; you have to turn over a lot of the latvian stuff, whereas the swedish you can more or less just take them as they come even for stud work)
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