How to bind 2 steels together

[marsaday]

I got my 2 steels into the attic yesterday and today i am tightening them together.

I am having difficulty getting the toothplate connectors to bind into the wooden truss. I still have to get all 17 bolts in, but reckon there will not be much more movement.

I am using a socket set to tighten the nuts up. Should i be using something else much more heavy duty ?

If this is it for getting the 2 steels to bind together what do you reckon to the idea of welding top connecting plates across the 2 steels. Say at 6 points. Would this be needed ?

View media item 25922

 

[^woody^]

I would not consider doing any welding in a loft space

What are you trying to achieve here? Looks like two steels with a timber beam between? The bolts are doing the holding together aren't they, why is a top plate required?

Why have tooth connectors been specified for steel to timber?

Finally those look like monster steels for a loft room. Have you thought this up yourself or is an engineer involved?

 

[theoldun]

Bulldog connectors are timber to timber. Not timber to steel. Take bulldogs out.
oldun

 

[marsaday]

Yep this is an engineer spec. But i think it is his first loft as he was a bit wooley on things. So i think he has over spec'ed to be safe.

The span is 8.6m and the dimension of the channels are 200mm x 75mm.

They are creating a sort of flitch beam with the roof truss which is in the middle of the room. At the centre of this truss stands the kingpost.

So the idea is to bind the 2 channels to the truss and he has used 3" toothed plate connectors to help with the binding. They have been welded to the back of the channels.

Yes there are A4 steel bolts binding the 3 parts together.

I need to have some welding done in the loft though, cant be avoided. this is spected in order to link the steels to the kingpost construction. L type brackets. They will bolt through the bottom of the kingpost and the L bit sits on top the the steel. Just needs welding. Or could i drill through and screw into the timber joist bolted in to the channels ?

 

[Deluks]

If you can borrow a 3/4" socket set with breaker bar you should have no probs. Spanner on the other side, let it spin til it hits something, locking it in place.

A4 stainless bolts? Hope you're only using them because you got 'em cheap.

 

[marsaday]

They are 8.8 bolts. Are these over spected then deluks ?

I have paid £160 for my rebar 8.8, washers and nuts. Lots of bolts used in bolting some joists together, putting wall plates on the wall and doing the big steel.

 

[Deluks]

No, right spec, but plain old galvanised steel would've sufficed and save you a few quid.

 

[^woody^]

I need to have some welding done in the loft though, cant be avoided. this is spected in order to link the steels to the kingpost construction.

In which case its a very bad specification. It will only take one stray spark and you will be looking at a spec for a brand new roof instead. If need be they should have been welded down on the ground

I still cant see why you need plates on the top of these steels - the bolts are securing them together

Your engineer should be designing economically, not over-designing because he is a bit unsure.

 

[marsaday]

Well the engineer was crap. I could see that when i told him we needed to trim round the chimneys.

Anyway it is done now. Are you still saying my steels are too big ? What would be a more normal size for my span. Basically i take the load off this steel flitch beam and go into the party and gable walls. the spans here are 3m and 3.55m.

My query still stands as to whether i need to add plates on top of the 2 steels to tie them together as the TPC are not biting as i would like into the truss. Do the bolts themselves do the job anyway ? He told me the TPC create a 3" loading area which is much stronger than a 12mm load which is the thickness of the bolt.

i have a copy of the truss frame diagram, but cannot upload it onto this site. does anyone want to see this ?

 

[Hitachimad]

Bolts/studding only need be bzp, grade 8.8
As for using stainless, thats plain stupid. Stainless bolts have a tendancy to bind up unless lubricated properly, are you having trouble doing the bolts up?
As for the tooth plate, thats a crazy idea, never seen that before! Put 18 bolts through a timber locked between to bits of steel like that, with the bolts tightened up, youd never move it!


With regarding to site welding, usually an easy way out for the engineer that cant be bothered to get up and measure up properly.

Cant see why the bracketry for the post couldn't be bolted onto the channel top flanges? 2 bits of decent sized RSA, bolted through the top flange of the channels.

Always the way with these jobs, the engineer says site weld, you turn up on the job, take one look at it and think of a much easier way, that could be done in the same time it takes just to get the welder out of the van.

Sometimes theres really no other way, but avoid site welding whenever possible

 

[marsaday]

the bolts are 8.8, not stainless. all bolted up now and seems ok. The toothplate connectors going into the truss dont go in that much as the wood is so hard.

The TPC make the load on each bolt spread over 75mm as opposed to the 12mm which is the bolt size. that is the engineers theory anyway.

You mention bolting the brackets onto the top of the steel. but how do you do this when there is a joist bolted into it already ?

Could i use screws instead, which will attach into the joist and through the top of the steel ? if so what size screw should i use. if i can do this i will not need a welder.

 

[Hitachimad]

Strange theory is that, surely the load is spread over an 8m x200mm area if the timber is touching the steel

I didnt notice the timbers inside the channel at first , not so easy then, you could drill and tap the channel, if your man is hapy to do that is another matter. The post is bearing down and only needs restraint at the base i assume. Or just weld it like hes said

 

[Deluks]

Mars: you mentioned A4, which is a grade of stainless steel.

Hitachi: The connectors, as mentioned spread the load of the bolt, so that the 12mm shaft of the bolt cannot 'tear' through the timber. Instead the washer takes the load and the bolt is sitting in the washer. Your 8mx200mm theory would work, if HSFG bolts were used?

As for the brackets, surely they could be screwed into the top of what's there. Pilot drill through the timber centre, or through the steel flange and into the timber beneath, and fix it down with good sized coach screws.

 

[marsaday]

Deluks - well i had to by 5 extra bolts from screwfix this weekend to get the thing clamped together. they were A4, so stainless. all the other bolts were just 8.8

So it is ok to just screw down into the timber plate, through the top of the steel. i wil email the engineer to ask about that. Will be loads easier i reckon.