Re-bar and mould oil.

Norcon · Posted: Sun Jul 11, 2010 6:29 pm

Thanks for all the advice (its much appreciated) and sorry if I caused any offence.

Fwiw I agree about taking the structure back to the ground entirely.
The cost of this would run well up to £10k. Perhaps more.
Perhaps the SE will lend a hand on the concrete breakers??? Does their insurance cover for mistakes like this?
Before the threaded bar was used quite a number of phone calls were made by the prinicipal contractor to the SE and roofing engineer who both gave the go ahead for these undersized anchors to be used.
God knows why.

The ones we have now are 30mm grade 8.8.
Which I believe has a tensile strength of around 150,000 pounds per square inch.

geraint · Posted: Mon Jul 12, 2010 9:17 pm

regsmyth wrote:

Thats some cantilever!

I'm suprised to hear that standard stud is ok as a replacement for HT holding down bolts. Especially if the stud is no larger than the spec HD bolts. Get it in writing and make sure BCO sees it.
I assume you'll use bolt boxes and washer plates, it gives movement with the full embedment depth.

whatever the strength of the holing down bolts... when they are covered over.. it means very little.. most holding down bolts will only be grade 46. i.e.soft steel...

Nice job!

geraint · Posted: Mon Jul 12, 2010 9:19 pm

[quote="geraint";p="1670263"][quote="regsmyth";p="1659848"]Thats some cantilever!

I'm suprised to hear that standard stud is ok as a replacement for HT holding down bolts. Especially if the stud is no larger than the spec HD bolts. Get it in writing and make sure BCO sees it.
I assume you'll use bolt boxes and washer plates, it gives movement with the full embedment depth.

whatever the strength of the holing down bolts... when they are covered over.. it means very little.. most holding down bolts will only be grade 46. i.e.soft steel...

geraint · Posted: Mon Jul 12, 2010 9:23 pm

regsmyth wrote:

Thats some cantilever!

I'm suprised to hear that standard stud is ok as a replacement for HT holding down bolts. Especially if the stud is no larger than the spec HD bolts. Get it in writing and make sure BCO sees it.
I assume you'll use bolt boxes and washer plates, it gives movement with the full embedment depth.

Nice job!

i have never come across ht holding down bolts... and never seen it specified what would be the point when it is encased...

regsmyth · Posted: Tue Jul 13, 2010 9:36 am

I've always used holding down bolts which are grade 8.8, which is a lot stronger than your standard grade 4.6.

The point is that if you use a high tensile bolt, the holes and hence edge clearances on your baseplate can be smaller than if you use grade 4.6, thus reducing overall steel costs.

Encasing them in concrete doesn't make them any stronger, but if they are fully encased, you don't need to worry about corrosion protection.

alittlerespect · Posted: Tue Jul 13, 2010 10:48 pm

Hi

The issue is to do with the design of the canopy being a cantilevered structure, the tie bars will be acting in tension to resist the overturning moment of the canopy and normal mild steel would not accommodate the embedded stress throughout the design life of the structure.
The concrete base/extension to the terrace is being used simply for its mass to resist the overturning moment and the only thing holding the roof in place are the tie bars.

Going by the SEs history he is likely to come back and ask for the 2 concrete pours completed to be demolished and rebuilt.
I would have anticipated costs for remedial works being nearer £20,000 rather than £2,000 mentioned!

Just for clarity the tie bars are not supporting the rear of the roof structure, they are there to stop the front of the canopy rotating and crashing into the terraces.

Regards

Norcon · Posted: Wed Sep 29, 2010 10:18 pm

Just an update. Jobs nearing completion now. These were a couple of snap shots I took a while back....

geraint · Posted: Thu Sep 30, 2010 7:40 pm

alittlerespect wrote:

Hi

Not wishing to cause any offence, but £2k sounds a ridiculously low amount of money to cover the reinstatement works.

I assume that in order to guarantee the integrity of the structure that the whole of the affected structure would have to be taken back to 'ground zero' and be rebuilt, rather than simply replacing a section of one or two columns?

As an aside I would like to mention that insofar as this discussion forum is concerned I am only making impartial comments and not providing unsolicited advice in any shape, manner, or form on what should or should not be done, and for these reasons the reader should place no reliance or relevance upon the comments that I make.

Regards

surely that cannot be a get out clause on a forum....