SE calculations

[^woody^]

Are these those same builders who couldn't get the floor right when they were not even out of the ground?

 

[Nathan110]

Yes, but I have to work with what I have. In this situation I just want to be clear if the SE should have provided a length or that was the remit of the construction company to work out the length was 4.7m instead of 4m

 

[Nathan110]

Also, if its up to the builder to decide a length of a beam does that not have any impact on the structural calculations etc. Seems a bit odd intuitevly to me but I'm not an engineer...

 

[tony1851]

I would be surprised if the SE took responsibility for the overall lengths of the steels; ideally this should be checked by the builder, and due allowance made for the additional length of the bearings.

The SE usually works on the clear span, and uses that dimension for the analysis of the beam. A few inches out either way will have little impact on the section of beam chosen as in a domestic setting there are only a few standard size beams which are useful.

If any of the beams are too short, they can be extended easily by short lengths of angle bolted or welded to the web, to save scrapping the beam and waiting for another.

 

[tony1851]

It's a 'chicken-and-egg' situation. Until the SE has calculated the loads, he/she will not know how long the bearings need to be. With a relatively lightly-loaded beam, the bearing may only need to be - say -150mm.

If the beam was heavily-loaded, it might need a longer - say - 300mm bearing.

Ideally the SE should do the figures based on the given clear span, and then show the minimum lengths of bearings. The builder would then make an on-site check of the clear span, and then add the lengths of the bearings.

 

[Nathan110]

That seems logical - add the bearing distance to the clear span. 4m +300mm +300mm padstone. Seems pretty straightforward to me. Was this a 'rookie' mistake by the construction company to order based on the span sizes as specified by the SE then? So frustrated by this, it seems so obvious :/

 

[freddiemercurystwin]

It is obvious, the builder measures the gap between the bearings and tells the steel supplier. The builder is at fault. But then the builder doesn't seem to know what he's doing.

 

[tony1851]

It is obvious, the builder measures the gap between the bearings and tells the steel supplier. The builder is at fault. But then the builder doesn't seem to know what he's doing.

But how would the builder know what bearing lengths to allow for, unless he had seen the calcs, or been told the bearing lengths required?

 

[Charlie George]

But how would the builder know what bearing lengths to allow for, unless he had seen the calcs, or been told the bearing lengths required?

But they had no bearing, using common sense you would allow extra if unsure ie 300mm for longer beams surely.

 

[Nathan110]

I'm with you. I just don't understand why the SE just doesn't add the bearing lengths to the clear span and give you a list of lengths to order. Surely paying £800 for these calculations, to add those measurements to give you lengths to order helps everyone. Unless there's compelling reasons not to do that... But no one has really explained why, especially when the SE came to the house and had everything explained

 

[freddiemercurystwin]

The builder knows the SO, he adds 300mm assuming 150 each side. If the bearings aren't written on the SE's drawings he phones him up and asks him.

 

[^woody^]

But how would the builder know what bearing lengths to allow for, unless he haad seen the calcs, or been told the bearing lengths required?

LOL. Seriously?

Lets pretend we are on The Chase

How does he know what beam to order if he has not seen .....

1. The calcs
2. The News at Ten
3. The daily horoscope

If it's sitting on a cavity wall say, what would the bearing be?

1. A steel ball
2. The direction of a compass
3. 100mm

If the builder has half a clue, he checks what before ordering?

1. His undercarriage
2. The engineer's calculations
3. The receipt from Asda

 

[freddiemercurystwin]

I'm with you. I just don't understand why the SE just doesn't add the bearing lengths to the clear span and give you a list of lengths to order. Surely paying £800 for these calculations, to add those measurements to give you lengths to order helps everyone. Unless there's compelling reasons not to do that... But no one has really explained why, especially when the SE came to the house and had everything explained

**** sake because as has already been mentioned the SE doesn't know if the builder's gonna build a wall in a different place, the drawings/survey could be a few hundred mm out, any number of reasons, the builder screwed up end of.

 

[^woody^]

But no one has really explained why

An engineer only specifies the bearings, but will calculate the beam based on the spans. If you add the two together, you get the length.

 

[Nathan110]

**** sake because as has already been mentioned the SE doesn't know if the builder's gonna build a wall in a different place, the drawings/survey could be a few hundred mm out, any number of reasons, the builder screwed up end of.

Thanks FMT,

The penny has dropped. Its basically to prevent any assumptions and so its not on his head.