Cracks under Steel Beam

[stevie888]

The builder has been paid in instalments but we've made sure we are behind the line regarding payment for work done and work still to be done. There is still a chunk ££ of the final quote outstanding

I have no idea if there is an SE, if there isn't he's in deep over his head as BC want to see the Calcs. I suspect there is an SE but the build may not comply with the specs he's been given. If the Specs he sends to BC are checked and seen to be inadequate - ie it's SE fault - then I assume he will have to have the specs reworked and resubmitted to BC for checking, agreement and the work rectified accordingly.

As an aside, as there is a crack in the blocks dead centre of the 10m beam, I presume it has sagged. I will measure along it tomorrow. If the beam was correctly specd by an SE, would you expect any sagging at all or non whatsoever ? ie is there an agreed max deflection inbuilt to calcs ?

I think you're in a fairly good position then given the circumstances.

As others have said beams have to deflect to build up resistance to the loading, just like a spring and on most domestic steels it's the deflection that determines the size required. That size increases dramatically as the span increases: your 10m span would need to be 16 times stiffer (the so called "I" value) than for a 5m span. I always advised clients to allow a support somewhere in the span if at all possible to let the sizes be more sensible. Often easy to work in a high unit in a kitchen with a bit of thought.

Strictly the allowable deflection relates only to the live component of the loading as that is what can vary and hence cause movement in the beam

 

[Dereekoo]

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That's just for serviceablity though and guidance to avoid cracking to finishes. It does not mean the beam has failed.

Indeed not, remove the load and the beam would spring back to its original shape

 

[tony1851]

All beams deflect under load , 1/360 or 1/300 span is the general max figure used in BS standards but can be tighter depending on the circumstances i.e. say above a glass partition (extreme case). At 10m the deflection could be 33mm which would be unacceptable in your case and hopefully the beam is sized to a lesser value

Remember that the 1/360 limit is usually for live loads only. The codes don't usually specify the deflection for dead loads and this is where a lot of problems arise. Unfortunately, much is down to engineering judgement and experience.

 

[Ivor Windybottom]

As an aside, as there is a crack in the blocks dead centre of the 10m beam, I presume it has sagged. I will measure along it tomorrow. If the beam was correctly specd by an SE, would you expect any sagging at all or non whatsoever ? ie is there an agreed max deflection inbuilt to calcs ?

You don't need any laser-guided instruments, just get yourself on a ladder at one end, shut one eye and look along it.

It it looks like a banana then you have a problem.

Blocks don't bend into banana shapes so they would crack from below upwards if the beam sags.

 

[billm]

Midway along the outer 10m beam is the crack in the block above the beam that BC identified. Is that due to flex, settlement, shrinkage or to be expected ?

The left end of the beam had the original cracked blocks - in my 1st post - that were replaced - and it still has an acrow under it

 

[stevie888]

The right hand end looks worse than the left TBH.

The crack looks like pure and simple beam deflection.

Overall it looks like a very curious layout: how different is your builder's version to what your SE originally designed?

 

[Koolpc]

I certainly wouldnt be happy with those cracks etc...

 

[billm]

The bottom plate looks to be rusty already, not been painted poss where it was welded by the beam supplier

 

[billm]

The right hand end looks worse than the left TBH.

The crack looks like pure and simple beam deflection.

Overall it looks like a very curious layout: how different is your builder's version to what your SE originally designed?

Totally different my son says but I never saw my sons SE's diagrams