Pre stressed lintels


Postby andy21275 » Sun Mar 07, 2010 5:23 pm

Hi all, I have just read today that concrete lintels are pre stressed. On watching my builder last week, he took a 2m concrete lintel and cut it in half to go over a sewer pipe before he built a 2m high cavity wall on top of the lintels. He did leave approx 150mm over both sides of the footings to bear the weight. Will these lintels be ok as they are now cut or will they just crumble.
All comments are much appreciated
cheers
andy
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Postby stoneyboy » Wed Mar 10, 2010 8:19 pm

andy21275,
Lintol should be fine. If they are undergroung the ends should be sealed to stop damp attacking the steel reinforcing bar.
end
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Postby elwood » Fri Mar 12, 2010 6:23 pm

Hi

Give the builder a break.

I've never seal a concrete lintel in my life nor as it ever been requested nor do I know anyone who as !

Bye
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Postby andy21275 » Fri Mar 12, 2010 10:21 pm

Ok thanks for your reply. The lintels are already in the ground, wall built and back filled, so no chance of me sealing them now, lets just hope they last afew years at least
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Postby stoneyboy » Sun Mar 14, 2010 6:02 pm

elwood,
The PCC lintols I buy are reinforced with what looks like wire rope. If these are used in a wet underground location I would expect rusting to take place from the ends.
What does take in time money and effort to spread a smear of silcone seal on the bare steel ends? Or more to the point what does it cost to replace the underground lintol if in a few years time the bearing ends spall.
end
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Postby chris_on_tour2002 » Sat Mar 27, 2010 12:00 am

it's actuall the steel bars that run through the concrete that are pre-stressed, not the concrete itself. during manufacture they stretch the steel reinforcers, putting them under tension. they then keep them under tension and pour on the concrete. the concrete sets and the steel remains tense, giving it a springiness with increases strength by resisting compression forces under load. cutting lintels is common and does not affect the strength, in fact it could be argued it makes them stronger by increasing the thickness to length ratio.
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Postby elwood » Sat Mar 27, 2010 7:46 pm

it's actuall the steel bars that run through the concrete that are pre-stressed, not the concrete itself. during manufacture they stretch the steel reinforcers, putting them under tension. they then keep them under tension and pour on the concrete. the concrete sets and the steel remains tense, giving it a springiness with increases strength by resisting compression forces under load. cutting lintels is common and does not affect the strength, in fact it could be argued it makes them stronger by increasing the thickness to length ratio.

And your point is ?

Bye
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Postby TheDoctor4 » Fri Jun 25, 2010 5:55 pm

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