Tie the Buddha Down

[KootK]

I'm working on the base support for a fairly large statue. It's 33m tall so roughly the equivalent of an elven story building.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[racookpe1978]

Thinking of the very base, at the connection between basic rock, concrete foundation, steel tower baseplates, and the copper statue suspended structure - kind of like the Statue of Liberty? with the copper skin outside of a structural tower?

For corrosion prevention (different electro potentials) and movement and thermal expansion and the very real probability of all the various parts of the sculpture moving at different rates at different times. Would you want to put a thin impermeable rubber or poly layers or sheets so that potential is stopped? Electro potential isolation would also require insulating shields for the bolts and fastener hardware.

Now, a gasket or sheet even 1/16 thick (1 -2 mm) would structurally require a "moment connection through the baseplate bolts" but would not the extra complexity of the structural loads be worth the avoidance of other problems?

 

[Ron]

KootK....while the structure looks a bit like a transmission tower, the skin is transmitting loads to the structure that a transmission tower never sees because of the openness of the structure. Torsion is an issue.

As well, there needs to be clear access to the turnbuckles as they will need to be tweaked as the load is placed on the structure.

I agree with the Dywidag anchors. Make them long enough that you don't have to worry about development. Cheap insurance.

Also keep in mind that your "11-story" structure does not have the dead loads of an 11-story building, so even if you are in the predominately lower wind zones of Canada, overturning might be an issue. You're catching a lot of wind area with seemingly little to resist at the base.

 

[BUGGAR]

Well, I don't see any structure to support the ears of the statue. I can't believe their structural engineers would not recognize such an oversight. In my experience, that is the first issue I would address. Have you contacted your client rep on this?

My recommendation would be to install a moment frame sideways to the main structure with a direct connection to the lobes of the ears. Simpson, et al, make pre-engineered moment frames that could tie the ears to the main structure. A moment frame would permit any required movement of the ears in extreme wind events yet retain them under major seismic forces. I see there is no public access to the ears of the statue which should shield your client from the inevitable litigation when swaying ear lobes throw someone to the floor.

Foundation? That's why most Buddha statues are sitting or lying down and have a big belly - it keeps them from falling over and thus they need no foundation, other than clearing people out of the way so the thing can be built.

Interesting project.

 

[KootK]

@racooke: dissimilar metals issues will be an issue for the designer of the superstructure. By the time that it gets to me, it's just a plain old carbon steel to concrete base plate connection.

@CEL: know of a good reference for the debonded/prestressed method? I've got a few paragraphs in a PIP document but that's it. Debond it all? Prestress to the max? Provide an anchor plate and use standard anchorage checks? Transfer shear via friction?

@Ron: torsion is an issue but it is primarily an issue for the superstructure designer. And rest assured that I plan to devise a base capable of resisting the applied loads. And "applied loads" will mean those supplied by the superstructure designer and verified by me. Keen observation with the turnbuckles. The supporting shaft will have an access hatch up the middle for just that reason.

@Buggar: I hear 'ya. The ear lobes will be liquid filled mass tuned sloshing vibration dampers. No public access.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[CELinOttawa]

There is a decent US Army Corp of Engineer's guide, but I'll be darned if I can find it online... Diwydag is a good place to start:

http://www.dsiamerica.com/products/geotechnic/dywidag-threadbarr-anchors/general-overview.html

Also, I would suggest that you have 1/2 to 2/3 bonded, depending on your specific situation, and use only a minor prestress. You're just looking to keep it all tight and allow for shrinkage, etc.

Generally I've anchored like this to bedrock, but in the case of the Alexandra bridge we "made" our own rock by pouring the old piers full of concrete. The techniques for rock are generally applicable for concrete, and conservative when used that way...

 

[Brad805]

This is a very interesting project. We have imported products from China (sunshades mainly), and the engineering can be a bit sketchy. When I asked about snow loads and drifts they seemed very puzzled. If they have an engineer registered in Canada, it could be fine, but it is the type of structure that some think falls outside the NBCC and that can lead to a headache if you are the only Canadian Eng involved (CSAS16/CWB Headaches/Steel worker unions...). Unless they have shown that they have a qualified engineer at this point, I too suspect you are amply more qualified to determine the anchorage forces and devise an appropriate base connection. While there is the liability issue from a contractual standpoint, I think this is a case where you might want to look into a few things to make sure. This is the type of project that makes the press and we all know what happens if there is ever a problem anyway.

I would research the Statue of Liberty to see what others have done with respect to dissimilar metals. Liberty had extensive repairs in 2012. I suspect you will be able to find a lot of useful discussions; however, if your role is limited to the foundation I doubt there is much for you to concern yourself with beyond the grout between the base and the Budda where it intersects your scope of works.

 

[cvg]

http://www.williamsform.com/Concret...te_Anchors/prestressed_anchor_advantages.html

 

[KootK]

@Brad: I can feel exactly those kind of headaches coming on I'm afraid. A bridge to be crossed when we come to it I suppose.

@Everybody: so we've got a concensus for prestressing. Why is that? If I told you this really was a braced frame for a mid-rise building and I was going with some good old F1554's, you wouldn't bat a collective eye. So what's so special here? And no, I was not able to maintain a straight face while typing that last bit.


The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[CELinOttawa]

What's different is a whole lot of things. Off the top I'd say:

- Lack of weight (as mentioned by others above).
- Lack of inspection/ease of access and maintenance (yes, I am assuming here).
- Lack of redundancy... This is not going to have the same number of connections as a midrise would.
- Lack of reliability/known conditions.

- Lots of "how the hell is all of this going to behave".
- Lots of secondary stresses (and potential for releases!) due to mixing of systems and materials.
- Lots of dubious workmanship.
- Lots of shrinkage (and potentially creep) in a mass foundation.

 

[chicopee]

Perhaps studying the construction of the Statue of Liberty may offer some clues.

 

[KootK]

Thanks for the list CEL. I should point out that there is actually a significant amount of weight coming down on the support structure. The entire statue (~200 metric ton) is supported by the steel skeleton frame.

I intend to go with a prestressed AB connection for all the of reasons supplied by contributors above. My scepticism regarding pretensioned anchor bolts is, in part, informed by the excerpt from PIP STE05121, shown below. In an application where construction quality is a concern, reliance on prestressing seems like it would exacerbate the reliability problem rather than alleviate it.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

The attached sketches (4 pages) show the preliminary concept for the statue support. I'd love to get some feedback on them. Note that I haven't done much with the column connection as, for now, that's still in the statue supplier's scope.

In discussing the column base connections with the statue supplier, two issues have arisen:

1) When asked about the column connections, the statue supplier recommended "just welding them down". Would that be feasible? Would there be issues with weld quality, fatigue, plumbing of the structure etc?

2) The statue supplier is insisting that the column size is as follows: wide flange; section depth = 200 mm; flange width = 500 mm. And no, I didn't miss type any of that. The statue supplier writes it that way and sends me pictures that reflect those dimensions. I can't find the section in any catalogue and, to be frank, the proportions seem unlikely to me. Anybody heard of such a thing?

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[EdStainless]

You might want to look at wind turbine foundations as a ref.
I saw one recently, 144 anchor rods, 150ksi steel, 1.5" diameter.
They were bolted into a ring that was set into about 8' of concrete, and then they projected enough to hold the base.

You might recall that when they rebuilt the Statue of Liberty all of the armature that contacted the Cu skin was replaced with 2205 duplex stainless steel.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[CELinOttawa]

I like your sketches, and the approach is a good one. I don't know if I am completely convinced as to the thicknesses, but I think we've confirmed that I tend to be more conservative than you...

I'd give serious thought to using an increased cover (2" or 2.5" as per bridge code) and a minimum of 35MPa concrete, as is required in parking garages these days.

As for the steel section, I have run accross these only second hand. I have a good buddy (childhood friend all the way through to University and beyond) who's an Engineer with ProSlide. They make what it sounds they make - Water slides. They often do business in China and he was telling me they have absolutely unbelievable sections that he couldn't see the purpose behind.

When dealing with chinese construction, you have to remember that they are a completely unique structural engineering tradition. They do not apply plastic analysis in steel, partly due to a long history of crap steel. Their steels are improving these days, but still aren't great. So it is likely that the section is compact in the extreme and made from 250MPa or so, low ductility, crap. That the welds theya are recommending are about as good an idea as our field welding was in the 1920s, with very poor notch toughness. Good luck with matching your electrodes... *sigh*

 

[CELinOttawa]

I went looking... Can't find that crazy section, but look at these numbers! CRAP!

http://www.steelfromchina.com/china-steel.html

 

[KootK]

I like your sketches, and the approach is a good one. I don't know if I am completely convinced as to the thicknesses, but I think we've confirmed that I tend to be more conservative than you...

Thanks for taking the time to check out the sketches CEL. I think that we're just conservative about different things in different ways sometimes. Which thicknesses are you concerned about? The mega-shaft thing doesn't depend on any connection to the roof slabs that tie in. It's a pure cantilever from the foundation below. At least, that's the story that I'm telling. Does that help on the thickness front any?

I'd give serious thought to using an increased cover (2" or 2.5" as per bridge code) and a minimum of 35MPa concrete, as is required in parking garages these days.

I think that you've touched on something that I'm also worried about. This is unheated space and there's really no building envelope to speak of. In that respect, it really does mimic a SE asia temple. I'll consider incorporating some parking standard durability requirements. That's clever.

Thanks for the Chinese steel info as well. I'll change my tack from assuming it's a communication error to assuming that it's a bizarre section (by NA standards at least). You called it right, the b/t on the flanges is freakishly high. The steel quality issue certainly doesn't make the "just weld it down" connection plan any more appealing.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

@EdStainless: thanks for your reply. Can you point me to anything that would show me how a turbine foundation is constructed? It's a ways outside my realm of experience.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[IRstuff]

Sees to me that you'd want a truss for the tower, but the cables don't give you truss.

TTFN
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Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

 

[KootK]

Tower by others for now IR.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[CELinOttawa]

The mega-shaft thing doesn't depend on any connection to the roof slabs that tie in. It's a pure cantilever from the foundation below. At least, that's the story that I'm telling. Does that help on the thickness front any?

Yes.