RSJ Joint - unusual and NOT to S.E. spec

[STORYTELLER]

Input appreciated here from someone of a Stress analysis/welding background.

My extension and knock through is becoming a comedy of errors during construction... never mind the unjustified extra charges!

S.E. specified this:

What the Steel Fabricator/Installer actually turned-up with and installed is this:

Which as you can see it nothing like the drawing. Now, I suspect the F@@ked up the smaller steel length (knock through wall between kitchen/diner) and and so welded a plate on the end and did the same over the awaiting web stiffener. I would have bounced it but had no idea of turnaround time and what it would have meant for the open back on my house!

What I am now concerned with is that this has gone from a bolted joint (holding up the house) into a Welded Joint... which to me seems less robust in terms of fail-safe. I know little about welded joints but it concerns me that the plates are welded to the ends of the webs/flanges... and not within, so if a weld fails.... there's no backup.... Then this obviously gets hidden under fireboard for decades..

I am wondering whether I should get an additional plate specified running under this joint - say a 10mm thk S355 steel plate with 4 bolt in the Main Steel and 4 bolts into the smaller Steel - 10.9 grade bolts.. (?). With the plate applying an upward reaction to the smaller steel so it is also a reinforcement of the weld, and not just a fail-safe...

I may be over-thinking this, but ...I don't know much about welds taking such vertical loads as imposed by a lot of the house.

I finally got hold of a stress justification for this... took 2 weeks... and I suspect was done after the work!

all input hugely appreciated.

BR,

 

[Harry Bloomfield]

Not an SE, but my main concern would be the diameter of those bolts, they appear too thin for the likely load. They look to be around M8, I would expect M16. Other than that, it looks as strang as the SE designed it to be.

 

[Murdochcat]

You really need to get your BCO involved rather than random internet advice

 

[STORYTELLER]

You really need to get your BCO involved rather than random internet advice

not sure what they'd do... but there are a lot of experienced people on here, so wouldn't say is particularly random...

 

[Murdochcat]

not sure what they'd do... but there are a lot of experienced people on here, so wouldn't say is particularly random...

Your BCO needs to inspect this before it’s closed up - so it’s in your interest to get them involved now

 

[Notch7]

What the Steel Fabricator/Installer actually turned-up with and installed is this

It doesn’t look particularly wrong, it maybe that the steel fabricator has done his normal detail rather than the engineers drawing.

The SE has specified a web stiffener that is shown as welded not bolted, the difference is the smaller steel sits into the web and so even if any welds failed, there would be no chance of collapse.

I have to say though I’ve had steels joined with plates welded in the end and bolted - and SE has been fine.


For peace of mind you need to get it confirmed by the SE - they can be funny about variations to design because their PI insurance guarantees their drawings and spec so they won’t simply agree to changes if it risks them being liable.

 

[Notch7]

Your BCO needs to inspect this before it’s closed up - so it’s in your interest to get them involved now

It really needs written confirmation from the SE, on the variation

And it definitely needs BCO to inspect before it’s closed up,

 

[STORYTELLER]

It really needs written confirmation from the SE, on the variation

And it definitely needs BCO to inspect before it’s closed up,

I know the SE drw shows welded stiffener, but its not loaded in shear as per what was delivered. yes, I got the steel supplier to send me a calc from a steels/stress engineer accepting responsibility... But creating a redundancy seems needed to me.... If you were going to create a face-face joint, surely you'd bolt to the Web of main steel... which is why I think it's a f@:k up

 

[STORYTELLER]

It really needs written confirmation from the SE, on the variation

And it definitely needs BCO to inspect before it’s closed up,

yes am assuming so... just not reassured that it's OK

 

[tony1851]

One of the reasons they normally bolt to the web of the beam (or as near to the web as possible as in your case) is to avoid torsion increasing the bending stress on the main beam.
The detail you have 'offsets' the load, so putting a twisting effect on the beam.

But its commonly done because its a cheaper joint to do, and your main beam looks big enough to accomodate the likely torsion forces.
As long as the weld looks continuous without holes or blobs, it wll be OK.
Those 4 bolts will be well-able to take the shear and bearing forces as well.

But as others have said, your SE will wash his/her hands.

 

[blup]

But as others have said, your SE will wash his/her hands.

Pay the SE to redo the calcs and knock it off the builders final bill

 

[blup]

You really need to get your BCO involved rather than random internet advice

Rrandom internet advice is just that but its proved useful to the OP.

 

[Murdochcat]

Rrandom internet advice is just that but its proved useful to the OP.

Maybe but it still hasn’t changed from the original problem

 

[STORYTELLER]

Maybe but it still hasn’t changed from the original problem

The main query was whether I could/should reinforce with a plate underneath given my questioning the changed design... this is what I still need input on... tho Tony feels its OK. BC just said to me what I thought they would say.. they will just check the joint based on what is agreed in way of the deviated design. For which I have the stress justification doc from the steel suppliers SE that I mentioned in the post.

 

[STORYTELLER]

One of the reasons they normally bolt to the web of the beam (or as near to the web as possible as in your case) is to avoid torsion increasing the bending stress on the main beam.
The detail you have 'offsets' the load, so putting a twisting effect on the beam.

But its commonly done because its a cheaper joint to do, and your main beam looks big enough to accomodate the likely torsion forces.
As long as the weld looks continuous without holes or blobs, it wll be OK.
Those 4 bolts will be well-able to take the shear and bearing forces as well.

But as others have said, your SE will wash his/her hands.

cheers for that. Yes it comes down to quality of weld at the end of the day it seems... You wouldn't consider a bolted plate across the bottom to be worthwhile?