mcerd1
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| posted on 3/2/09 at 01:40 PM |
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quote:
Originally posted by richardlee237
If you really cannot certify the design with the remaining bolts by calculation then it is always possible to weld on an extension to the base plate
and bolt that down to the foundation. Thus restoring the original calculations.
but on these sites there is no site welding allowed - its all galvanised 
quote:
Originally posted by richardlee237
The CDM Regulations were brought in to eliminate, amongst other things, the "she'll be right" attitude.
yeah, but its a total PITA in the wrong hands.....
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richardlee237
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| posted on 3/2/09 at 02:11 PM |
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Yes, I know what you mean.
But,
Here in Yemen the concept of Health and Safety barely exists let alone the legislation and practice. Some of the accidents are appalling.
Normal workwear is a pair of sandals, even in the local steelworks !
Quote Lord Kelvin
“Large increases in cost with questionable increases in performance can be tolerated only in race horses and women.”
Quote Richard Lee
"and cars"
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BenB
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| posted on 3/2/09 at 02:54 PM |
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Health + Safety. What like this??? Absolute quality 
 
Description
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rachaeljf
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| posted on 3/2/09 at 03:17 PM |
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Hi Robert,
I am a structural engineer, but of course I'm female so feel free to ignore me.
This isn't much help but to put things in perspective the NSSS allows for bolts to bent under load up to 3 degrees. This is not explicit, but is
implied by tapered flange members not needing tapered washers unless the taper is more than 3 degrees.
Even grade 8.8 bolts have good ductility and will probably be ok, but unfortunately the only way to know is to examine the affected bolt for cracks
before and after it is straightened; not very easy with the structure in place!
What you could do is break out the concrete under the baseplate to expose some unbent bolt. Then cut off the bolt below the bend and fit a coupler.
This could be done with the base plate in place but it's a rigmarole.
How about installing a new resin anchor in line with the two bolts on the affected side of the column and fix a small beam (100x100x15 RSA perhaps)
over the base plate, thus effectively clamping the base plate down?
The above thread does sadden me; the days of "engineering judgement" made by experienced civil engineers do seem to be fading fast. My
field, railways, seems to be the last bastion! I have to laugh when I see consultants produce reams of FEA to proudly proclaim their fixing bolts have
a safety factor of 40+, while they say nothing about the 130 year old structure they want to fix to.
Cheers R
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mcerd1
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| posted on 3/2/09 at 04:50 PM |
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quote:
Originally posted by rachaeljf
How about installing a new resin anchor in line with the two bolts on the affected side of the column and fix a small beam (100x100x15 RSA perhaps)
over the base plate, thus effectively clamping the base plate down?
I'd love to do sonething like that but the type of base doesn't make it easy and the customer wants it to look like there wasn't a
problem 
this is the type of thing - horrible isn't it, it starts off good, but then needs bits stuck on at the top
quote:
Originally posted by rachaeljf
The above thread does sadden me; the days of "engineering judgement" made by experienced civil engineers do seem to be fading fast. My
field, railways, seems to be the last bastion! I have to laugh when I see consultants produce reams of FEA to proudly proclaim their fixing bolts have
a safety factor of 40+, while they say nothing about the 130 year old structure they want to fix to.
we get that sort of thing all the time, but some one normally comes in at the last minute and says "is that existing concrete strong enough for
all that?"
and then you need to start again..... (I just do the steel and alloy bits )
quote:
Originally posted by rachaeljf
I am a structural engineer, but of course I'm female so feel free to ignore me.
I know better than that, the one and only girl on my course at uni was alot better at it than me
[Edited on 3/2/09 by mcerd1]
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rachaeljf
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| posted on 3/2/09 at 05:12 PM |
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Right,
You have no moments carried to the feet of those legs because the towers are lattice structures. You will only have tension and/or shear shared
equally between all the HD bolts for each leg base. Therefore it's likely you can get away with 3 of the 4 HD bolts working. If so, you can
straighten the bent bolt and put a nut on it just for looks.
If you do need the 4th HD bolt to work, what you can do is cut off the bent bolt flush to the base plate. Then diamond core the base plate hole a bit
bigger to take a sleeve nut over the cut off HD bolt. The diamond core will also need to take out some concrete so you have enough thread to screw on
to. If you get a sleeve nut turned up to look like a simple nut and washer, and screw in a dummy M24 stud sticking out the top, no one will ever
detect the "deliberate mistake!"
Cheers R
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mcerd1
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| posted on 3/2/09 at 05:44 PM |
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there is actually a bit of moment at the bases, but its not that much (now that I've actually looked at it properly  it actually took a few
hour just to find out which structure had the problem! )
I like the idea with the sleve nut
I don't know if they'll go for it in this case, but its worth a shot
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rachaeljf
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| posted on 3/2/09 at 08:48 PM |
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The base moment on any leg will be insignificant and results from the geometry, mainly because your truss forces don't go exactly through the
centroid of the base connection. It's not worth bothering about.
How badly bent was this bolt anyway?
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mcerd1
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| posted on 3/2/09 at 11:06 PM |
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quote:
Originally posted by rachaeljf
How badly bent was this bolt anyway?
they don't seem to know 
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Aboardman
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| posted on 3/2/09 at 11:08 PM |
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I am sure some of the engineers where i work must have come across this problem ( they are ex arups, Buro happold).
I will ask them in the morning.
But if the structure is up how did the base plate fit over it,
has the top of the bolt bent after installation?
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