/ Calculating a steel beam size.

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George Fisher - on 17 Jan 2013
Can a UKC structural engineer point me in the direction of a steel beam calculator?

What info is needed to work this out? I have an opening with a span of known length. a solid stone wall sitting above with a known height and thickness. Sitting on this wall is a slate roof which I can give most or all of the sizes, angles, construcion etc.

Is there anything to stop me working out how much steel I need to support this?
krikoman - on 17 Jan 2013
In reply to George Fisher:
>
> Is there anything to stop me working out how much steel I need to support this?

No but I think the building regs and insurance will need calculations from a certified engineer.
In reply to George Fisher: got a pretty simple, basic beam calculator programe I could email across to you, it's an MS-Dos programme, so only small and realyl basic!

ebygomm - on 17 Jan 2013
In reply to krikoman:

Building regs don't always require calcs. I agreed size of beam on site for ours, no calcs needed.
RHirst - on 17 Jan 2013
In reply to George Fisher: I'm assuming your going to do this without building regs.?
Should you decide to sell in the future a switched on surveyor may pick up on the alteration and it could throw a spanner in your works..
Get some calcs done professionaly, photograph everything you do then you can always get retrospective regs later..
Have you considered glulam beams rather than steel? Look up Lamisell beams.
You could speak to their tech dept.
Neil Williams - on 17 Jan 2013
In reply to ebygomm:

I've heard of DIY calculations before for a house extension, with full building regs approval. I think he did the calculations himself then substantially overspecified to make sure, and they were happy with that.

Neil
George Fisher - on 17 Jan 2013
In reply to George Fisher:

Thanks for replies.

The architect has come through now so all sorted. Just wanted to speed things up for the builder in the architects absence.

All being done with building regs, I just like sticking my oar in I guess.

For anybody interested it was 2x 150x90mm
fxceltic on 17 Jan 2013
In reply to RHirst:
> (In reply to George Fisher) I'm assuming your going to do this without building regs.?
> Should you decide to sell in the future a switched on surveyor may pick up on the alteration and it could throw a spanner in your works..
> Get some calcs done professionaly, photograph everything you do then you can always get retrospective regs later..
> Have you considered glulam beams rather than steel? Look up Lamisell beams.
> You could speak to their tech dept.

just looked them up and saw they have been used in my local community centre recently, small world!

Nutkey on 17 Jan 2013
In reply to krikoman:
Buildings control will take calculations from anyone.
House insurance won't care, but if the thing falls down and it was your fault, they will probably not pay out.



JH74 - on 17 Jan 2013
In reply to George Fisher:
> (In reply to George Fisher)
>
>
> For anybody interested it was 2x 150x90mm

Side by side so you can get insulation between? What was the span and steel thickness? 12mm? Based on nothing I was suprised by the smallish dims..
vincentvega - on 17 Jan 2013
In reply to JH74:

Im often suprised at how often 6x4s are specd. I have fitted loads that size, and must be fine as they are calculated, usualy the span isnt large. I just over think things!

Just fitted a right big girl today. A 6m, 300x300. Weighed in at just over 500kg!!
Jim Fraser - on 18 Jan 2013
In reply to George Fisher:

In civilised countries, we have systems for ensuring that the people who make these decisions are the ones who were listening in the maths class when they were at school.

Having said that, the whole thing is a bit over-played and the confidence in Eurocodes is not always warranted.
subalpine - on 18 Jan 2013
In reply to Jim Fraser:
>
> In civilised countries, we have systems for ensuring that the people who make these decisions are the ones who were listening in the maths class when they were at school.
>

umm ok <opens basic statics book>

a light rod AB of length 6m is supported at A and B and carries a weight W at C, where AC=2m. find the shearing force and bending moment at any point of the rod..


MG - on 18 Jan 2013
In reply to subalpine: but we have a beam with uncertain loading with uncertain support conditions etc
subalpine - on 18 Jan 2013
In reply to Jim Fraser:

a uniform beam 10m long and mass 2kg/m is supported horizontally at ends with a 30 kg mass 4m from end. calculate shear forces and max bending moment
subalpine - on 18 Jan 2013
In reply to MG:
> (In reply to subalpine) but we have a beam with uncertain loading with uncertain support conditions etc

yeah, i reckon most structural engineers etc would not be able to solve most of the examples in humphrey and topping's intermediate mechanics..
MG - on 18 Jan 2013
In reply to subalpine: if the above are examples, I think they would cope.
MG - on 18 Jan 2013
In reply to subalpine: If you want a challenge try this:

Built in beam. No load. Linear elastic. Linear thermal exanpansion. Uniform thermal gradient so the middle surface does not change tempature. What is the deflected shape?
Jim Fraser - on 18 Jan 2013
In reply to George Fisher:

Trainee stuff. (Well it was in 1978 as I recall.)

The latest laws covering these matters, European and UK jurisdictions, are strange mix of intelligent precautions, stupid errors and restrictive practices. For instance, you are not allowed to tighten up a bolt properly on European structures these days (Hilti guys agree with me but then they can because Lichtenstein is not in the EU member.) and you have to be a Chartered Structural engineer to approve a simple beam calc in some jurisdictions.

John_Hat - on 18 Jan 2013
In reply to Jim Fraser:
> (In reply to George Fisher)
>
> In civilised countries, we have systems for ensuring that the people who make these decisions are the ones who were listening in the maths class when they were at school.
>

Kind of yes, but having been the kind of person who was qualified to calculate the sizes of steel beams, so many simplifying assumptions are used and standard tables and values applied that actually calculating it accurately never occurs.

For a start, a real, live, honest-to-goodness pin jointed frame rarely exists.
ads.ukclimbing.com
needvert on 18 Jan 2013
In reply to Jim Fraser:

Seems expected to me, given other aspects of our society.

Connection failures are sudden, incorrect bolt tightness could lead to this.

While simple beam calcs are indeed simple, loading is often not so simple. Dead loads are easy, regular live loads a bit more tricky, then add in wind and earthquake loads.

To draw an analogy to the medical profession, in my country I can't access antibiotics or the more effective pain relief medication without a prescription. I find this a pain in the ass, the token visits to crowded medical centers, not free naturally, to get a prescription, but oh well.
subalpine - on 18 Jan 2013
In reply to Jim Fraser: i like the sound of a structural engineer. what qualifications do you need?
subalpine - on 18 Jan 2013
In reply to MG:
> (In reply to subalpine) if the above are examples, I think they would cope.

well, simple examples from an a level book, yet no answers..
needvert on 18 Jan 2013
In reply to subalpine:

In a lot of the world one would go like this:

- Start & Finish structural/civil engineering degree
- Get job at engineering company
- [optional] Become a chartered engineer

It's a respectable field, at the core of civilization. If you're a technically minded person, it's even relatively easy.
John_Hat - on 19 Jan 2013
In reply to needvert:
> (In reply to subalpine)
>
> In a lot of the world one would go like this:
>
> - Start & Finish structural/civil engineering degree
> - Get job at engineering company
> - [optional] Become a chartered engineer
>
> It's a respectable field, at the core of civilization. If you're a technically minded person, it's even relatively easy.

Agree. I did 1, 2 and was midway through 3 when I got made redundant.

The comment above about live loads being complex is true, but you don't design steel beams for complex live loads, you make a blanket assumption of 5kn/m2 or similar and design for 1.6x Live + 1.4x Dead, and then round up the answer to the next standard beam size above where your calculations come out.
loopyone on 19 Jan 2013 - host217-42-138-168.range217-42.btcentralplus.com
In reply to George Fisher: when we had a wall knocked out our builder used 'experience' to calculate/guess the beam needed. an engineer friend has since confirmed that he was smack on right with the beam. the builders advice was that building regs were only important in cases where you remove a wall if your planning on selling fairly soon or the building/wall in question is particularly complex or of an unusual construction.
Jim Fraser - on 19 Jan 2013
In reply to John_Hat:
> (In reply to needvert)
> [...]
>
> Agree. I did 1, 2 and was midway through 3 when I got made redundant.

Sounds familiar.

Jim Fraser - on 19 Jan 2013
In reply to tatty112:
> (In reply to George Fisher) when we had a wall knocked out our builder used 'experience' to calculate/guess the beam needed. an engineer friend has since confirmed that he was smack on right with the beam. ...

I think that's called luck.

I have come across several cases where people have made such judgements and it has all gone wrong. Nobody killed so far but that's simply luck. Many of those have involved bad fasteners design or installation. Others have involved ignorance about the forces involved or people making judgements outside the range of their experience without applying appropriate calculation and intelligent judgement. Some have been agricultural structures and some have been marine structures.

Typically, there are thousands of guys out there who will do you a set of drawings for a barn at a good price but it is really a warehouse for a lowland industrial estate and the first moorland storm or heavy snow load will wreck it. There are some issues with renewables where the engineering is rather new and some individuals and organisations who want a slice of the action are too wedded to the past.

The search for intelligent life goes on.
loopyone on 19 Jan 2013 - host217-42-138-168.range217-42.btcentralplus.com
In reply to Jim Fraser: a good builder should be able to make an intelligent judgement on a beam based on similar houses they have done before.
Jim Fraser - on 19 Jan 2013
In reply to tatty112:
> (In reply to Jim Fraser) a good builder should be able to make an intelligent judgement on a beam based on similar houses they have done before.

And what credible tools for an intelligent judgement on such a matter does the good builder have?

We have to get a grip of the fact that buildings stay up for a reason. Older buildings are still there because all the weaker old ones have fallen down. The ones that are still there weren't necessarily better designed: they often just had a bigger pile of decent stones available or the ground beneath them happend to be better. Modern ones usually stay up because someone with a bit of inteligence understood the materials thoroughly and understood the ground beneath them.

In the 21st century, we expect high standards. We need to get a grip of what that means. Most politicians weren't listening in maths and science at school otherwise they could have got proper jobs. This can result in poor judgements about what is required for technical legislation. In spite of that, most European legislators get it right a lot of the time thanks to extensive consultation.

Mistakes have been made in legislation about fasteners in construction and about foundations. The foundations are usually too good and the fasteners are often too poor. We pay for the former in cash and the latter, well, that remains to be seen.

loopyone on 19 Jan 2013 - host217-42-138-168.range217-42.btcentralplus.com
In reply to Jim Fraser: having had a surveyor who made a (wrong) judgement about the chimney in our last house I would suggest it's a mixed bag and an experienced builder can make a judgement about a steel in a lot of cases that will be correct.

incidentally a friend of ours who bought a house a few years ago spent a lot of money to have detailed (and as it turned out completely inaccurate) surveys done which have since cost over 150k to rectify issues not recognised.

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