Deflection/Settlement/Cracks

[padstar]

I have now received the calculations (lots of them and very confusing with tables, graphs and models) and they have given the following;

The main opening will be constructed in a "Goal post" style with a column either side sat on a new foundation and the beam split into 3 sections as below;

Columns UC 254x254x132

Beam is 2 No. UKPFC 430x100x64

This will apparently give a max deflection of 11.9mm at the mid point and 7mm at 2m from the columns. The columns themselves have a max deflection of 2.5mm

 

[tony1851]

Wow!! Those beams will be nearly 18" deep! Surely not necessary on that span?

Presumably the PFCs are being fixed together to make a 'compound' beam - they would be too slender if left separate. If they are being joined, they are usually fixed the other way, thus ][ with welded and bolted spacers between them (not tubes, hopefully).

Anyway, thanks for the update, and good luck with the project.

 

[noseall]

Jeeezus effing Christ! 132kg's per metre, that's some chunky steel, right there.

 

[^woody^]

I'll get the NHS to drop off a spare ventilator to site. You'll need it.

BTW, what does the SE's Risk and Method statement say regarding handling and installing under CDM. What? He's not sent it yet. Get away.

 

[noseall]

BTW, what does the SE's Risk and Method statement say regarding handling and installing under CDM.

Would this be considered normal work in terms of PL insurance or will the insurers bracket the works as civil engineering or some such?
I hope they have room for a crane.

 

[tony1851]

@op:
if your floor-to-ceiling height on the ground floor is around the usual 2.6m for houses of that age, the beam is going to stick down 0.4m, so your headroom under the beam will be around 2.2m, ie not much higher than door-height.
The room will look claustrophobic and you will get the feeling that you have to duck under the beam. If your bedroom floor joists run parallel to the back wall, you might be able to push the beam up a little, but not by much and that method often causes its own problems.

It's often easy to criticize other's designs, but this case shouts out as unusual. Has your SE really looked at alternative beam-depths, or is he just accepting what the spreadsheet has churned out? Admittedly 9m is a long span and deflection is an issue, but it's hard to believe that a 305 deep beam wouldn't suffice?

And as for those columns!..........He's probably specified them to get a sufficient number of bolts in to make a rigid connection with the beam, which suggests he might have designed it as a 'moment frame' to take lateral wind load as well? But surely a lighter column would be OK?

 

[noseall]

surely a lighter column would be OK?

One inch thick flanges FFS! I think the whole thing is bonkers.

 

[padstar]

@tony1851 I have asked him to look at a 305 deep beam and will let you know what he says. The upstairs joists (200mm) run parallel with the external walls so had assumed the steels could sit half in the floor floor void and then drop below the GF ceiling by 200mm leaving a rough clearance of 2400mm floor to ceiling. As you rightly point out i don't want a beam bellow 2.4 ideally.

 

[noseall]

the steels could sit half in the floor floor void

Using up the floor void comes with its own set of problems - mainly running services. Have a plan ready for getting pipes and cables etc across.
Be sure that the beam (top) is set so that it doesn't interfere with any floor coverings. We plan where any knock-throughs are and make sure the beam is low enough at these points to allow floor boards etc.

It may sound daft but I had to address a job whereby the chaps correctly put the beam in level but the house wasn't. The low point in the house coincided with the high point of the beam and a door opening.