RSJ Bearing question - do I need to fix?

M

Michael Lewis

Joined
18 Aug 2022
Messages
5
Reaction score
0
Country
United Kingdom
Looking for some input (help) guys.

Padstone is 80mm in depth. RSJ has been installed to sit on the concrete pad and bricked in on the inner leaf of the cavity wall.
RSJ - 2 * 203 x 133 UB
RSJ open span - 4.3m
Note: also has a point load from additional beam in centre (additional beam 2.2m)

Due to beam deflection the steel is not fully sitting on the padstone (IMG_3868). I've measured and there seems to be approx. 50mm opening, leaving me to think that the steel is sitting on approx. 30mm of padstone.

My question is - is this ok? if not how best to remedy?
Builder long gone so can no longer take up with him.

Note: the beam sits offset to the right on the concrete padstone. SE did confirm this is ok.

Thanks in advance. Really stuck with this one.
 

Attachments

  • IMG_3868.jpg
    IMG_3868.jpg
    359.1 KB · Views: 266
  • Padstone (005).png
    Padstone (005).png
    599.5 KB · Views: 233
Somewhere between doubtful and highly unlikely. Beam design should come with a specified bearing and padstone (or other means of bearing) What does the design specify?
 
Hi Jeds,

Original SE design has bearing at 100mm width. The issue I have is that the beam is installed, boarded and plastered.
Is there a way to remedy from the external wall?
if it must be remedied internally then so be it. Just not sure what the solution here would be.
 
Also - is the beam deflection and resulting gap underneath expected?
Just wanted to know if ok that the steel is sitting on approx. 30mm of padstone.
 
It's normal to butter the padstone before placing the beam. If the load is high, I normally specify shims set back from the face of the padstone - to direct the load through the centre. You can measure the true deflection with a string line stretched end to end. Measure at the supports and at the centre - the difference is the deflection. I wouldn't mind betting the problem is more the padstone not being level than excessive deflection.

looking at the end photo a bit more closely, it looks like the beam is bearing over 100mm but you are saying that only about 30mm is touching. If so you could probably resolve that by injecting structural grout into the gap.
 
If the beam has deflected so much as to lift the end of the beam off the padstone, that's serious.

If the padstone is not level creating the gap, that's remedied with some cement grout.
 
Thanks Jeds & Woody, I didn't even think about the padstone not being level.
How would I know whether the padstone is level or whether the beam has deflected so much as to lift the end of the beam?
Difficult to run a spirit level across the depth of the padstone as the builder has bricked around the beam.

The beam is now boarded up. I'm guessing there is no way for me to check beam deflection without tearing apart?

Just to note, the original SE's calcs passed the beam design as valid. To double check I contacted another SE to conduct an independent check of the beam. They also confirmed the beams have sufficient capacity to handle the load.
 
I'm wondering if the actual problem is that the pad stone wasn't cast / installed level? It might be that the beam was never bearing onto the pad stone properly.

It probably wouldn't be an issue if the pad is made from C35 concrete, as the bearing area probably won't be any where near the block's crushing strength, but for peace of mind it wouldn't hurt to get some free flowing grout into the gap if possible.
 
You wouldn't have to fully expose the beam- each end and the centre will do, top flange or bottom flange, whichever is easiest. String will show any gross deflection (not sure if I fully understand your pics but to effectively shorten the beam by 50mm it would have a fairly sizeable bend on it) or a cheap laser level (my cheapie lets you lock the beams so you can have straight line that's not necessarily level. Handy trick at times)
 
Cheers RoonyRayGun & oldbutnotdead.
Great idea for measuring beam deflection. will defo be exposing small sections at the ends and middle to measure deflection.

@RonnyRaygun, i'm sure the padstone is made of high strength concrete so hopefully will be ok.

@oldbutnotdead, fortunately the beam hasn't been shortened by 50mm, but the gap between the beam and the padstone is 50mm. Only 30mm of the steel is sitting on the beam rather than the full 80mm. 50mm is slight raised.

I've engaged with the SE to review potential issues with bearing. Just waiting on a list of questions he has. Will keep the post updated.
 
@tlan said:
Both wrong. https://www.metals4u.co.uk/materials/mild-steel/mild-steel-universal-beams-rsj/11741-p
Click to expand...
That site is patently wrong; there is no such thing as a 'mild steel universal beam RSJ'.

The correct term for the OPs beam is Universal Beam.

Rolled Steel Joists (no longer produced) were originally made for the mining industry, where their compact but heavy and strong sections were useful. They were rolled in a different way to modern beams. They have tapered flanges, which needed special tapered washers.
We occasionally come across them in refurbishment work.
 
You must log in or register to reply here.
Back
Top