SimonD Posted January 20 Share Posted January 20 I'm now about to embark on getting my bridge done almost as per details below. We've decided on using a timber deck, which is simply plain treated deck board with build in grip strips. We've change our minds about the balustrade and I though that given the whole top floor of the house is timber, we ought to just go with a timber balustrade. Couple of things I'm pondering. 1. We're actually going to install the deck boards across the bridge not along it so I need to think of the best arrangement to modify the direction of the joists, bearing in mind that the span along the bridge for the joists would be almost 4.8m. Any neat suggestions? 2.how best to fix the balustrade timber posts to the steel columns - do I fix with hollo bolts directly or do I need a bracket which in turn is fixed to the column using hollo bolts? 3. how to detail and make the balustrade itself. 4. any other suggestions ideas on detailing the decking to look nice, especially at the edges just beyond the steels - should I just leave a little bit of a cantilever, or would some kind of edging/frame at the end of the deck board look better? Link to comment Share on other sites More sharing options...
BotusBuild Posted February 12 Share Posted February 12 On 20/01/2024 at 19:25, SimonD said: install the deck boards across the bridge not along it Keep the joist layout as shown, and add in noggins between along a centre line that runs from one end to the other. Each board will then be supported at each end and in the centre. You may want to install a piece of wood on top of each side beam to attach the boards to, and so the top of the noggins would also need to be at the same height. On 20/01/2024 at 19:25, SimonD said: how best to fix the balustrade timber posts to the steel columns "steel columns" or "steel beams"? Does this drawing make sense? The red is the steel beam cross section, the brown rectangles are a wooden "filler" on the left, and the wooden balustrade on the right, the blue lines are coach bolts that hold the wood to the steel - you may need a single (stainless/galvanised) steel plate on the outer side of the balustrade act a "clamp" and stop the heads of the coach bolts disappearing off into the balustrade wood as you tighten up the nuts on the inside of the steel beam. On 20/01/2024 at 19:25, SimonD said: detailing the decking to look nice, especially at the edges just beyond the steels My personal preference would be edging to hide the steel beam, unless you don't mind the industrial look. I hope the above helps 1 Link to comment Share on other sites More sharing options...
SimonD Posted February 12 Author Share Posted February 12 1 hour ago, BotusBuild said: Does this drawing make sense? Thanks, yes makes sense. The bridge is made of steel box sections so bolts need to be hollo type which causes a bit of a headache. The longest I can find are max total fixing depth of 86mm so notching would be a must, plus they're so big, 33mm diameter hole is required through the posts. If I use Cedar, then stainless ones are over £100 a piece so 2k in total just for these ☹️ If I had my workshop, which is all in storage, I'd fabricate some brackets, which I think may be the only option but prices I've received to make them up also seem a bit ridiculous, but maybe I'm just tight? 😉 Link to comment Share on other sites More sharing options...
BotusBuild Posted February 13 Share Posted February 13 Instead of Hollo Bolts, what about some M12 stainless steel threaded rod right through the box section, with a nut on either end? Link to comment Share on other sites More sharing options...
markc Posted February 13 Share Posted February 13 15 minutes ago, BotusBuild said: Instead of Hollo Bolts, what about some M12 stainless steel threaded rod right through the box section, with a nut on either end? Even better if there is access to put tubes inside the box to prevent deformation of the box walls and subsequent flex in the posts. Link to comment Share on other sites More sharing options...
BotusBuild Posted February 13 Share Posted February 13 50 minutes ago, markc said: put tubes inside the box to prevent deformation of the box walls Agreed, although at 8mm thickness there won't be much deformation unless you go mad with the torque wrench Simon, they wouldn't need to be welded in place, so not too difficult to do if you can get inside the box section (just a bit fiddly perhaps) 1 Link to comment Share on other sites More sharing options...
joe90 Posted February 13 Share Posted February 13 15 hours ago, SimonD said: The bridge is made of steel box sections so bolts need to be hollo type which causes a bit of a headache. The longest I can find are max total fixing depth of 86mm so notching would be a must, plus they're so big, 33mm diameter hole is required through the posts. I had not heard of holo bolts before (basically rawlbolts for steel?). However can you not fix the holobolts to the steel then remove the short bolt and replace it with a standard long bolt through the posts ?, the holobolt becoming a captive nut with the box section @ 8mm thickness? Link to comment Share on other sites More sharing options...
markc Posted February 13 Share Posted February 13 32 minutes ago, joe90 said: I had not heard of holo bolts before (basically rawlbolts for steel?). However can you not fix the holobolts to the steel then remove the short bolt and replace it with a standard long bolt through the posts ?, the holobolt becoming a captive nut with the box section @ 8mm thickness? Yes you can swap the fixings once the hollobolt (big Rivnut) has been set. 1 Link to comment Share on other sites More sharing options...
Alan Ambrose Posted February 13 Share Posted February 13 I don't know what corrosion protection you're planning, but maybe 'rivnuts' e.g. https://www.accu.co.uk/knurled-flat-rivet-nuts/69619-HRKN-M6-16-A2 Use a homemade or bought in setting tool. Link to comment Share on other sites More sharing options...
JohnMo Posted February 13 Share Posted February 13 Bit of an observation, from the drawings the drop looks quite big, so do you need a structural design to ensure your design is robust enough? To bolt through box section, you would normally have a sleeve over the bolt, the sleeve fits inside the box section and is just slightly shorter than the overall box section dimension and acts as a compression piece, so you do not compress the box when all is tightened Link to comment Share on other sites More sharing options...
SimonD Posted February 14 Author Share Posted February 14 On 13/02/2024 at 12:07, joe90 said: I had not heard of holo bolts before (basically rawlbolts for steel?). However can you not fix the holobolts to the steel then remove the short bolt and replace it with a standard long bolt through the posts ?, the holobolt becoming a captive nut with the box section @ 8mm thickness? This is what they look like as used for fixing all the joists to the steels. No possibility of removing and then replacing the bolt as the whole fixing is the structural element. On 13/02/2024 at 12:40, markc said: Yes you can swap the fixings once the hollobolt (big Rivnut) has been set. On 13/02/2024 at 12:42, Alan Ambrose said: I don't know what corrosion protection you're planning, but maybe 'rivnuts' e.g. https://www.accu.co.uk/knurled-flat-rivet-nuts/69619-HRKN-M6-16-A2 Use a homemade or bought in setting tool. Thanks both, you've put me onto Rivnuts as an alternativ option but I'm struggling to find structural data for the rivnuts used for wider sections. On 13/02/2024 at 09:25, BotusBuild said: Instead of Hollo Bolts, what about some M12 stainless steel threaded rod right through the box section, with a nut on either end? This is something I briefly considered but followed the guidance of the SE and suggested fixings. I may just review this as an option. On 13/02/2024 at 12:46, JohnMo said: Bit of an observation, from the drawings the drop looks quite big, so do you need a structural design to ensure your design is robust enough? It's 3 meters drop so yes, I need to ensure it's robust enough. Currently the only option I know I can use is Interclamp/Kee Clamps tube clamp arrangements and depending on post diameter, I can install them up to 2m centres. Essentially what I want to do is come up with a design we like and then pass it by the SE as a final nod. 1 Link to comment Share on other sites More sharing options...
joe90 Posted February 14 Share Posted February 14 Not heard of rivnuts either (led a sheltered life me) these however would need inserting on the other side of the box so the bolt would extend right through the box section (better stability?) however would it crush the box section when tightened? I can see benefits in both and guess your SE would specify which was best 🤷♂️ Link to comment Share on other sites More sharing options...
JohnMo Posted February 14 Share Posted February 14 14 minutes ago, joe90 said: Not heard of rivnuts either (led a sheltered life me) these however would need inserting on the other side of the box so the bolt would extend right through the box section Thing with rivnuts you drill a hole in a plate or box section on the side you want to bolt. They go in the hole and you deform them so they compress against the base material. They don't go on the opposite side of the box section. Used hundreds building cars and kitcars. 1 Link to comment Share on other sites More sharing options...
joe90 Posted February 14 Share Posted February 14 Every day is a school day 🤔 Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now