Can and RSJ bend?

[Ashworth1]

I put an rsj (158x89-16kg) in . It's 6 meters in length - sitting on 150mm either side.
It is taking ceiling weight, which is obviously not much. However now I am knocking through unnoticed where the roof has been extended over they have put a layboard on my existing rafters (that were sitting on the wall that is being knocked down). I have extended my rafters into the web of my steel.
By looking at the existing rafters it's hard to see how much weights is on them but doesn't look much.
So my question - has anyone experienced them bending under an excessive load? My structural engineer has moved country!
Thanks

 

[bobsuerita]

No wonder he moved country that rsj sounds too small over that span with roof bearing and yes they do bend

 

[bernardgreen]

has anyone experienced them bending under an excessive load?

Yes Bent and buckled but it was subjeced to an excessive load.

My structural engineer has moved country!

Then find another one and have him or her calculate the loading on the RSJ

Note.. the horizontal force from rafters is often overlooked and the RSJ is then undersized for resisting that force and bends sidways,

 

[^woody^]

They bend under their own weight

 

[John D v2.0]

Yes usually deflection is what the SE is limited by when they are calculating beam sizes. It will usually take a lot more before it actually fails, but when it does it won't be pretty.
When you say you are doing the work unnoticed, does that mean you don't have building control involved? There's a good reason they ask for calculations!
Ideally you should prop anything putting load on the beam and get an SE to calculate what beam is actually needed.

 

[wessex101]

My gut feeling is that is a long span for a rather slender beam. The fact that you go on to say it is only taking the ceiling and then throw in as an after thought that it also taking the rafters is rather worrying.

Who calculated the loads? As other suggested you need to get it checked by another structural engineer.

 

[Ashworth1]

Sorry that was I typo - ' I noticed '
I do have planning permission - I got calcs done. I'm just not sure the SE had taken into consideration that a layboard would be put on existing rafters.

 

[wessex101]

A layboard doesn't generally make that much difference. The load from the new roof is usually only nominally increased compared to the weight saved by removing the tiles from the existing roof.

If the engineer was working from accurate drawings and allowed for the load from the rafters then you can only assume it is OK. You could always post a copy of the calculation sheet, there are some people on here who understand that stuff.

 

[noseall]

Yes they do deflect. We ended up fixing battens to a ceiling owing to the deflection of 3 beams that were installed with the beam bottom flush with the top of the wall plate.

The roof purlin was point loaded onto each beam via a 100mm x 100mm wooden post. The roof was a standard semi, hip end extended out, repeating the hip end format. Beam span was aboot 2.6m.

They each deflected 8mm in the middle. We actually tried to take some of it out by gently acro-ing the beam ends and using packers. All we achieved was more bend in the beam and decided to leave them as they rested.

 

[noseall]

I put an rsj (158x89-16kg) in . It's 6 meters in length - sitting on 150mm either side.

I bet that beam looked proper daft over that span!

P'S. There is no such beam as a 158mm x 89mm. Ask Tony, he loves 152mm x 89mm beams

 

[Ashworth1]

Update...
I finally tracked the SE down. He advised me he didn't calculate roof load when doing the calcs!!!
The 152x89 (over 5 meters) was for ceiling weight only.
So pis%#d off.
It's hard to see how much weight is actually on the lay boards. Few pics.
The first 3 are of the existing rafters that are sitting on the 152x89 beam
The 4 th photo is on the other side which has a layboard that will sitting in 2- 7x2" timbers bolted together (3 m span)
The 5 th pic is a 7x2" timber bolted together that sits on a supporting wall and in the 152x89 beam. This will have my exisiting joist hanging off them and now existing rafters as there is a small layboard on them.
The final pics are of my existing purling/brace coming off of it. It's strange as where the brace comes off the existing purling all that weight is sitting on a timer that is spread out the whole roof span that sits on ceiling joists!!! Not a supporting wall.
Appreciate all your advise. My building inspector has actually passed everything so far. To be fair when the new roof was pitched the existing had a membrane over it so he obviously didn't notice it.
Do you think there are ways to deflect the weight somewhere else or would you advise bigger beams?
Many thanks

 

[rssteve]

What has he se advised you do?

 

[John D v2.0]

Wow so your SE has really cocked up, presumably he wasn't told to exclude the roof load, for an SE to miss that without a good excuse is basically negligent!
I think he should explain what to do structurally, but regarding the negligence it's just lucky you picked it up.

 

[tony1851]

I bet that beam looked proper daft over that span!

P'S. There is no such beam as a 158mm x 89mm. Ask Tony, he loves 152mm x 89mm beams

You are soooo amusing.

 

[tony1851]

I'm not surprised his SE has left the country; a 152-deep beam on a 6m span