ASTM A588 steel plates cladding for a city's landmark 1

[HBMetals]

Dear engineers, I am not sure whether this is the right place to pose this question. Recently one of my friends is working on the refurbishment of our city's landmark - Liberation Monument(please see the photo attached). This monument, about 31 meters tall, was made of giant stones about 30 years ago. Now he wants to clad the whole monument with atmospheric-resistant steel plates(ASTM A588) which may have a deliberately controlled rusty color. This monument is very important to the city and we have to be very careful,

1)The city is located in northern part of China very near to Beijing, typical temperate and monsoonal climate. Well, we also have the No.1 heavily polluted air, notoriously known as the haze and fog. Is this material(A588) suitable to use in this environment? Which grade of the steel is better? What is the minimum thickness of the cladding steel plate?

2) Moreover, since it is kind of the symbol of the city, we want it to last for a long time, say 60 years at least. Can A588 plates last for such a long time? Is it possible we can cotrol the color of the rusty surface? Do different weathers(rain, snow, fog, wind, etc) in four seasons change the surface color of the cladding steel plates dramatically?

Your help is highly appreciated. Thanks in advance.

Hebei Metals Industrial Limited
www.hbmetals.com

 

[racookpe1978]

Usually, that style of self-preserving (rusted metal rejuvenating) metal looks poor up close (where people can see it clearly) or near stone or concrete because of the staining effect of the particles on the supports and piers below. In your case, I expect the artwork to look worse over time as stains build up. Bronze does not wash off as readily in the rains (and air pollution common now to China) and so bronze statues still look good hundreds of years later.

 

[HBMetals]

Racookpe1978, thanks for your prompt reply and advice. Bronze may be a good idea. However, instead of changing the whole stone monument to bronze statue, the municipal government at present just consider a metal sheet cladding. Could you please recommend a bronze specification for sheets / plates suitable for this application? Thank you. (I only familar with C95800 which is used in valves)

Hebei Metals Industrial Limited

http://www.hbmetals.com

 

[hokie66]

Before the monument is cladded, has the structural soundness been confirmed? What type stone was used for the original cladding? Is deterioration of the stone the reason for the intended refurbishment?

 

[dhengr]

HBMetals:
You should be talking with steel suppliers who would supply this type of material to you, for their recommendations on the various details. They may have some experience and color samples of their product, for your area. You are talking about cladding the stone base of the monument, right? Then, this cladding would have few structural requirements other than self weight and lateral loads from wind, EQ, maybe vehicle impact. The US products meeting ASTM A588, weather to a fairly nice mellow brown, fitting into natural settings very well. One of their disadvantages is that they weather slightly differently depending upon their direction of weather exposure; they tend to streak a bit if there is a large/regular wash of water over some small areas as opposed to others. They also have a nasty feature of staining areas below them, due to their water runoff, such as concrete piers, foundations, pavements, etc. Thus, it might be wise to install a 1 or 2' wide drainage system around the monument base, a splash and sloped drain area, which drained to the city drain/sewer system. This would catch most of the staining rain water runoff, without streaking the pavement over a larger area. Also, you need a good water tight detail at the top, around the cast base for the horse, et.al., to keep water out from behind the cladding. Otherwise, you could clad the stone base with copper panels, or some such, on a light support frame system, but this might be slightly less resistant to impact or vandal damage. Is your friend’s problem primarily that the stone base is deteriorating from the local atmospheric conditions?

 

[hokie66]

dhengr, I thought he was talking about the tall thing in the background. I wouldn't think the statue is 31 metres high.

 

[dhengr]

Hokie:
Your guess is likely slightly better than mine. I think you are right, I just thought that was some large bldgs. in the background. Damn metrics vs. ft.-n-inches. I did see that 31 and thought, will the stone base is about 10-12' high, so three times that gets you to the top of the rifle clip, and gave it no more thought. Now, I even see that the people at the base of the statue are probably sitting, so my scale is shot in any units of measure. But, what fun would it be these days, if they didn’t let us guess for a few days before they gave us some meaningful engineering info. relating to their problem? Most of my comments are still valid, but with the taller structure, the splash area has grown a bit.

 

[EdStainless]

1) I am not sure what surfaces he is looking to clad wither.
2) A Cu or Cu alloy would be a better option if cosmetics are the main concern. A light acid wash after installation will accelerate the formation of a nice natural patina.
weathering steels will take a long time to develop patina and it will not be uniform.
The other problem is that if it where someone might try washing it they can damage the patina.

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P.E. Metallurgy, Plymouth Tube

 

[HBMetals]

Dear Hokie66, dhengr & Edstainless, thanks for all your valuable advice. I didn't reply them yesterday because of time difference. For clarification, we are talking about the refurbishment of the 31-meters(102 feet) monument behind the horse statue. You are right, hokie66, the refurbishment work is required due to the deterioration of the stone. I just get more details from my friend. The main body of the monument structure was made of concrete and steel. Then its surface was cladded / covered by marble tiles which became unsteady(can't adhere to the surface firmly) on the surface. In the concern that the marble tiles might fall off and hurt people, the municipal government intended to replace all tiles with some kind of sheet metal. Their requirements are simple:

1)Safety - the new cladding material must adhere to the surface firmly and withstand different weathers.
2)Nice Looking & Long Lifespan - It is a symbol & landmark of the city and has some political implications. A gorgeous face is necessary as well as a long lifespan.
3)Interchangeable or Convenient Maintenance.

Provided above-mentioned points are met, usually there is no budget limit. So shall we try to use bronze metal sheet? Which metal grade is suitable for this job? Moreover, could you please recommend a THICKNESS for the sheet? Since we expect it to withstand severe weathers with a light mass。 Thank you very much.

Hebei Metals Industrial Limited

http://www.hbmetals.com

 

[hokie66]

OK, now we understand. Removing the marble tiles is the way to go. But there is a lot more to consider before you choose a material for the recladding. What is needed is a system, not just a material. I think China has a plentiful supply of granite, so why not replace the marble with the more enduring stone?

http://failures.wikispaces.com/Standard+Oil+-+AMOCO+Building+Marble+Facade+Failure

 

[BUGGAR]

The City of San Diego considered a tall waterfront structure clad in titanium. It was architectural so I ignored it, but the Architect had strong reasons for specifying titanium.

 

[EdStainless]

Ti, stainless steel, and Cu alloys have all been used for architectural applications.
Ti would work well in your polluted environment, it would stay looking the same (a dull matt silver) forever.
But the Ti would need to be fully supported by underlying structure since it is expensive and very thin sheet is used.

As much as I like stainless steel, and as successful as it has been I hesitate in suggesting it for your environment. You would have to use a higher performance alloy such as 2205. It is strong enough that it could be a self supporting jacket. This alloy has a good record, even neat the sea shore.
Stainless and Ti have the advantage of not changing, needing no maintenance, and not discoloring anything near by.

http://www.ssina.com/download_a_file/architect.pdf

http://www.imoa.info/molybdenum-use...nless-steels/stainless-steel-architecture.php

Cu alloys (brass or bronze) are the traditional material for statues and monuments. It would need to rely on the existing structure for some support since these alloys are not very strong. And the runoff will discolor the area around it.

http://www.copper.org

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P.E. Metallurgy, Plymouth Tube

 

[dhengr]

HBMetals:
I suspect that they have a case of fairly flexible structural elements w.r.t. lateral loads, with insufficient lateral bracing, and then tried to attach a very inflexible veneer of marble slabs to it, without sufficiently flexible joints btwn. the slabs, and without a cladding support system which would tolerate the movement. It is a piece of modern sculpture which paid little attention to the actual structure and its action, except that the entire thing should not fall over. Obviously, environmental conditions can come into play too. If the cladding is significantly attacked by air pollution, or the cladding joinery leaks and allows water behind the cladding, or if the cladding support system does not tolerate the structural movement, you will end up with problems in fairly quick order. I think your friend should get the original design drawings and make sure he understands how the structures work and deflect before he goes too much further. Then, a complete cladding system design solution is in order, as Hokie suggests. I would talk with local/national cladding suppliers for your options and their recommendations and guarantees on that account.