Structural steel work calculations

[aidan.f]

I had  an extension built 'before covid' now just finishing  BC checks and have been asked  for  'structural calculations' My architect is now unobtainable (maybe dead?)
This is from his drawing..

Span in two sections  not  exceeding 5.6 metre 2 no. x 254 x 254 x 37 UB's bolted together with 10mm diameter bolts at  500cc seated upon 300 x 200 x 150 high  concrete pad stones

That reads like a quote from standard design tables.
Happy to pay a professional to state 'this is well engineered' but maybe if I can quote from source  I could push back to BC and tell them that design is standard.
My as built span is 2.6 metres, the steels are supporting 2.5 m of external wall plus existing and extension roof loads.




 

[pcolbeck]

I think you need calculations from a proper structural engineer. We did for something similar for our extension.

Strangely a friend has just had massive amounts of work done and needed calcs for all the steelwork but used a massive reclaimed pitch pine beam in one part of the house instead of a steel. Its the biggest span in the house (replaces a complete internal supporting wall) and as its wood no structural engineers report needed apparently. Doesn't make any sense but there you go.

[Little Jim]

The local authority are not really interested in the calculations per se, just who takes the can when the steel fails, in other words they want to see some calculations (or other justification) for the steel used from someone with some valid PI insurance.  Many years ago I did my own calculations for some lintels on an extension we built, they were much simpler as I just needed to work out the loadings and then look up the relevant lintel in the manufacturer's literature.  As I was not a qualified structural engineer the LA just made me use one size bigger of each lintel, and the building control officer admitted that my calculations were "probably" correct. 

[Kim]

Strangely a friend has just had massive amounts of work done and needed calcs for all the steelwork but used a massive reclaimed pitch pine beam in one part of the house instead of a steel. Its the biggest span in the house (replaces a complete internal supporting wall) and as its wood no structural engineers report needed apparently. Doesn't make any sense but there you go.

Regulations are written in blood, so presumably it comes down to the relative rate and severity of historical fuckups.  I'd expect wood to be self-limiting in that respect, on account of the size of trees.

[cygnet]

I've never seen a standard design table like you might find for lintels and purlins.
You can find steel section properties and limits of resistance here: https://www.steelforlifebluebook.co.uk/ but it requires additional calcs to justify section selection.
(per exams, "show your working" and as Little Jim said; "show your PI")

Technically the beam sizes given are listed as UCs, not UBs

The connection description

bolted together with 10mm diameter bolts at 500cc

is very sparse, and BC should be interested in that too.

[rafletcher]

Strangely a friend has just had massive amounts of work done and needed calcs for all the steelwork but used a massive reclaimed pitch pine beam in one part of the house instead of a steel. Its the biggest span in the house (replaces a complete internal supporting wall) and as its wood no structural engineers report needed apparently. Doesn't make any sense but there you go.

Regulations are written in blood, so presumably it comes down to the relative rate and severity of historical fuckups.  I'd expect wood to be self-limiting in that respect, on account of the size of trees.

More likely because wood is not homegenous, so there's no way to carry out meaningful calculations.

[FifeingEejit]

Strangely a friend has just had massive amounts of work done and needed calcs for all the steelwork but used a massive reclaimed pitch pine beam in one part of the house instead of a steel. Its the biggest span in the house (replaces a complete internal supporting wall) and as its wood no structural engineers report needed apparently. Doesn't make any sense but there you go.

Regulations are written in blood, so presumably it comes down to the relative rate and severity of historical fuckups.  I'd expect wood to be self-limiting in that respect, on account of the size of trees.

Oversimplification: Wood also makes a shit load of noise before failing, Steel doesn't, it just goes.

[LittleWheelsandBig]

Panoramix OTP is an engineer specialising in timber. I think he does plenty of strength calculations.

[Tim Hall]

Presumably all those timber frame houses have had relevant Hard Sums applied to them too.

[LittleWheelsandBig]

I had to learn a bit of the fundamentals of timber engineering in year 2 or 3 of my degree.

[aidan.f]

Thanks all, just  filled in one of those online bingo forms.. hopefully not  too much  spam coming my way