weld vs plates

[deuce]

Hi.

I have just fitted a few steels in my roof and the engineer had me bolt them together instead of welding.

I was unsure of why he stated to bolt it.

An old school welder that lives near me said that weld is much stronger and 1" of weld will hold 1 tonne.

Can someone please clarify it.

Thanks.

 

[the snooper]

are you a coded welder if not could he be sure that your welding would be up to standard and would he risk being part of that ?

 

[deuce]

Hi.

I am not a welder.

I am in the process of refurbing a property and I just wanted to know out of curiosity.

Thanks.

 

[stormin]

The old adage that 1" of weld will hold 1 tonne, but what size is the weld and what size are the plates?
The problem with weld on site is controlling the quality, gas shield getting blown away, getting welding gear into roof area, prepping the plates. All stuff that is easier done in the shop. Bolting on site is simpler and the fact holes are generally 2mm oversize allows a bit of play for tolerances.

The real reasoning is in the design. A fully bolted connection is treated as a pin ended connection and transfers negligible moment or torsion to the member it is connected to, the beam is therefore designed as simply supported. A fully welded connection is usually treated as a moment connection were both moment and torsion loads are transmitted between interconnecting members.
Your roof members will have been designed as simply supported by the engineer for simplicity.

 

[Hitch]

Much easier to weld plates on in a workshop, and bolt the connection together in your loft. You should be capable of bolting it together, but perhaps not welding it.
That ol 1" o weld holding 1 tonne is piffle really, it depends on how the joint is designed, and what material and how big the weld is.

Most spec 6mm fillet as standard usually.
Usually only ever weld beams in lofts etc if the engineer is too idle to measure and design it properly. Then the problems of bits not fitting seems to become the problem of the welder.

 

[Welderpaul]

The old adage that 1" of weld will hold 1 tonne, but what size is the weld and what size are the plates?
The problem with weld on site is controlling the quality, gas shield getting blown away, getting welding gear into roof area, prepping the plates. All stuff that is easier done in the shop. Bolting on site is simpler and the fact holes are generally 2mm oversize allows a bit of play for tolerances.

The real reasoning is in the design. A fully bolted connection is treated as a pin ended connection and transfers negligible moment or torsion to the member it is connected to, the beam is therefore designed as simply supported. A fully welded connection is usually treated as a moment connection were both moment and torsion loads are transmitted between interconnecting members.
Your roof members will have been designed as simply supported by the engineer for simplicity.

Stormin pretty much covers this. Any fabricator i know would be shouting at an engineer who specified site welding when bolting could be used to form the connection. Much easier to put a few bolts in that drag a welding set out to weld them. Bolting probably 50x quicker?
Lost count of the amount of times i hear 1" of weld will hold 1 tonne. Load o rubbish.

 

[deuce]

Thanks for the reply.

I have already fitted my steals in the roof and it is now all complete.

The reason I was asking was purely for educational purposes.

A friend (who is a builder) takes on quite a few jobs that require the fitting of steals and one that has recently cropped up was a job whereby he has to fit a 5 metre length across a shop front to support the wall above.

The engineer has got it down as one full length, but it is nigh on impossible, so he is advising the engineer to re calculate using 2x2.5m steels bolted together.

I said to him that he should just weld them to save on costs, but he then said that plating them is a stronger connection.

The old guy that lives by me used to work on ships and when he saw what I was going through when I installed mine, he said that they could have just been welded (it is stronger than plating).

I just wanted to know which is stronger to end this argument.

Thanks.

 

[Welderpaul]

One of the issues with joining two steels end to end with plates (splice) which form a beam is that it is difficult to stop them sagging in the middle. Quite often we would join with a splice plate which is what is specified by the engineer, prop them in place then weld to prevent droop.

Not really answered your question have i . I would think Dune is your man for that...he may be along soon.

 

[deuce]

Thanks Welderpaul.

When I fitted mine I had to put a plate on either side of the web and top and bottom.

I didn't see it sag although it probably has a bit.

 

[Welderpaul]

Flange?

Aye, thats the other way - we rarely end up putting plates on the outsides of flanges - they always seem to get in the way of something that is going up against the underside of the beam.

 

[mike os]

Aint that the truth LOL

if it is unsupported mid span structural steel should be installed in a single length if possible (does not mean it is nessesarily the easiest) Any join needs to be properly designed and spec'd for the job in hand, anything else is unnacceptable as a structural element (ie you need an engineer & he needs to provide design & calcs for inspection)

Generally any join will impact on the strength & integrity of the beam ( not always negatively....but too often for comfort)

Welding and bolting (or indeed riveting) both have their place and afaik there is no reason for one to be prefered over the other except for the reasons given in other posts... i e ease on site

 

[stormin]

If you were to try and splice a beam with a bolted connection, you need several things. Either saw cut beam ends for good bearing or fitted end plates, also the beam webs and flanges must be bolted together using high strength friction grip bolts torqued to correct settings to eliminate all movement in the joint and possible sag.

It's possible to do but in this case a full strength butt welded joint would be a better method of getting the full moment capacity of the beam. Best not to put the weld joint in the centre either were max bending load occurs. Splitting the beam into three with welds at quarter points would be a better bet, or two thirds one third if you only want to do one welded joint.

An engineer may insist of plating over the bottom flange joint also to reduce the risk of failure of welds in tension.

 

[mike os]

quite..... & by the time you have done all (and all the paperwork, hot works etc..)that 99% of the time you could work out a way to get it in in one....