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Construction related questions.

Construction related questions.

Old Dec 19th 2011, 4:12 pm
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Default Construction related questions.

Alright so I have been reading about wall saws for the past 2+ weeks. I had no idea they were soo bloody expensive. I don't understand the high cost considering it is not a precision equipment, is pretty simple and straight forward technology and theres isn't much material cost.

I have bought many high end toolroom machinery made in Switzerland , Germany and the US and can't understand why something like a wall saw (hydraulic or high frequency electric motor) cost as much as precision metal working equipment.


The Pentruder hydraulic wall saw is my dream machine but no idea on cost but won't be surprised if it is the most expensive brand considering the equisiteness of the machining . Pentruder is made in Sweden.
http://www.pentruder.com/


So next up is Hilti's hydraulic models. I Googled to find price and the only luck I had was for a used one in Abu Dhabi. The chap in Abu Dhabi wants $50,000 How much did this thing cost new?? I can buy late model CNC precision lathes or mills new or used for that price or less so I am just baffled as to why it costs soo much.
http://abudhabi.dubizzle.com/classif...ic-wall-saw-3/

Heres some Hydraulic models from Husqvarna but I am pretty sure they are made by Dimas of Belgium and just branded Husky.
http://www.priorityplant.com/Wall-an...C16-40-1-0.htm

------

Ok next question.
When I lived in Abu Dhabi, I liked watching building being constructed, I love to see how things are made.

What I remember is that all the high rise building support columns were made with a rebar skeleton encased in concrete. Like the apartment towers on the Corniche near the Volcano fountain. I used to live in Baniyas Tower and used to watch the apartment block across the street go up. What I don't understand is why use a rebar skeleton instead of I-Beams. In the US I notice they use I-Beams, even for 2 or 3 story commerical buildings.

-------

Lastly, just noticed this very recent article about the UAE cancelling/putting on hold nearly $1 trillion in construction projects.
The value of construction projects scrapped or on hold in the UAE soared to $958bn in the 12 months to October, Citigroup said Tuesday, signalling the Gulf state’s battered project market is still some way from recovery.
http://www.constructionweekonline.co...s-total-958bn/
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Old Dec 19th 2011, 6:34 pm
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Default Re: Construction related questions.

wall saws are fairly complex with the hydrualic power packs, clutches, cooling systems and ability to basically generate huge rotational power. Not sure if any other portable machine can be compared to it. but those prices seem very high, also the cost of the blades (all diamond encrusted) are high and with a poor operator you can burn one out very quickly.
People now try to use wire saws where possible as they are much cheaper. Also if you are using this type of equipment usually it means someone somewhere has made a **** up.
Steel versus concrete is simple cost economics, where labour is cheap concrete wins out. Also up to certain heights steel is unenconomical (in commercial or residential work) but not in warehouse type stuff. Also over certain heights concrete is uneconomical ....lots of factors but basically your average designer can price the scheme on budget costs for each type and decide from there. Concrete also offers less complications with fireproofing and the like.

Anyhow there are many many factors in each design to make the choice
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Old Dec 19th 2011, 11:49 pm
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Default Re: Construction related questions.

Originally Posted by weasel decentral View Post
wall saws are fairly complex with the hydrualic power packs, clutches, cooling systems and ability to basically generate huge rotational power. Not sure if any other portable machine can be compared to it. but those prices seem very high, also the cost of the blades (all diamond encrusted) are high and with a poor operator you can burn one out very quickly.
People now try to use wire saws where possible as they are much cheaper. Also if you are using this type of equipment usually it means someone somewhere has made a **** up.
Steel versus concrete is simple cost economics, where labour is cheap concrete wins out. Also up to certain heights steel is unenconomical (in commercial or residential work) but not in warehouse type stuff. Also over certain heights concrete is uneconomical ....lots of factors but basically your average designer can price the scheme on budget costs for each type and decide from there. Concrete also offers less complications with fireproofing and the like.

Anyhow there are many many factors in each design to make the choice
Thanks Weasel.

The steel in the buildings I mentioned is encased in concrete just like with rebar construction. In the US they use I-Beams , be it 3 story commerical buildings or high rises. I woulda thought that even if one puts the cost of labour at negligible for the UAE, the added time it takes to build a rebar skeleton compared to I-Beams would see the latter being chosen.
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Old Dec 20th 2011, 2:00 am
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Default Re: Construction related questions.

Originally Posted by Boomhauer View Post
Thanks Weasel.

The steel in the buildings I mentioned is encased in concrete just like with rebar construction. In the US they use I-Beams , be it 3 story commerical buildings or high rises. I woulda thought that even if one puts the cost of labour at negligible for the UAE, the added time it takes to build a rebar skeleton compared to I-Beams would see the latter being chosen.

they did build one from steel

http://www.khaleejtimes.com/DisplayA...section=theuae
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Old Dec 20th 2011, 7:14 am
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Default Re: Construction related questions.

Originally Posted by Boomhauer View Post
Thanks Weasel.

The steel in the buildings I mentioned is encased in concrete just like with rebar construction. In the US they use I-Beams , be it 3 story commerical buildings or high rises. I woulda thought that even if one puts the cost of labour at negligible for the UAE, the added time it takes to build a rebar skeleton compared to I-Beams would see the latter being chosen.
The difference is huge for example take one typical column in structural steel, supply and install could be $1,500 per tonne, so a typical column might cost you $2-3,000.
For the reinforced concrete maybe 0.4 tonnes of reinforcing and even allowing 3 cubic metres of concrete per column and labour for one day, I estimate I might get the column complete for less than $750.
The only difference is the length of time taken to complete one versus the other, where labour is negligible you solve this problem by having 10,000 guys on site.
Like I mentioned before the overall purpose of the building after, what codes it must meet, fire proofing, sound proofing, seismic, end use, MEP services etc within the building and logistics of building are going to play a major part in the choice.
Also and speaking specifically about the ME, tenderers here will lie, lie and lie so a guy proposing a concrete building will claim to his naive client that he will build it as fast as any other method. When faced with that information the client will pick the cheaper price, even though he ought to know (or be advised of) some the realities.
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Old Dec 20th 2011, 8:58 am
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Default Re: Construction related questions.

also we have lots of mountains to turn into cement here, and no environmentalists to object
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Old Dec 20th 2011, 1:05 pm
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Default Re: Construction related questions.

The I-beams are covered in concrete not for the concrete's strength, but for fire protection. Steel loses much of its strength very quickly in a fire, so a multi-storey steel-framed building without adequate fire protection of the structure is a no-no.

The re-bar in concrete structures is there because concrete is strong in compression, but weak in tension or shear. The rebar adds to the tensile / shear strength of the concrete.

So, what you've compared are two entirely different structures: one, a steel structure with concrete for fire protection, and the other a concrete structure with steel for tensile / shear strength.
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Old Dec 20th 2011, 1:21 pm
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Default Re: Construction related questions.

Originally Posted by Bahtatboy View Post
The I-beams are covered in concrete not for the concrete's strength, but for fire protection. Steel loses much of its strength very quickly in a fire, so a multi-storey steel-framed building without adequate fire protection of the structure is a no-no.

The re-bar in concrete structures is there because concrete is strong in compression, but weak in tension or shear. The rebar adds to the tensile / shear strength of the concrete.

So, what you've compared are two entirely different structures: one, a steel structure with concrete for fire protection, and the other a concrete structure with steel for tensile / shear strength.
not to nit pick but yes i am going to anyhow

The steel encased in concrete is not always for that reason, in some high rise you cannot achieve the design (well with reasonable sizes) through rebar hence you achieve the area of steel using a steel section in the concrete.

Also its more typical to fire paint the structure than to encase in concrete for the protection and its a lot faster or cheaper than creating concrete forms around the structural steel.

Plus of course there is no mass concrete construction well for this type of building, all in situ concrete is reinforced.
Structural scheme is just a method of doing the same thing, be it structural steel, precast concrete, in situ reinforced concrete, prestressed, or post tensioned. The first choice is invariably cost led more than any other reason.

2 days to the holidays ..yes i am bored

Last edited by weasel decentral; Dec 20th 2011 at 1:24 pm.
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Old Dec 20th 2011, 1:32 pm
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Default Re: Construction related questions.

Generally, though...

(But well picked, nit)
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Old Dec 20th 2011, 2:32 pm
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Default Re: Construction related questions.

Originally Posted by Bahtatboy View Post
The I-beams are covered in concrete not for the concrete's strength, but for fire protection. Steel loses much of its strength very quickly in a fire, so a multi-storey steel-framed building without adequate fire protection of the structure is a no-no.

The re-bar in concrete structures is there because concrete is strong in compression, but weak in tension or shear. The rebar adds to the tensile / shear strength of the concrete.

So, what you've compared are two entirely different structures: one, a steel structure with concrete for fire protection, and the other a concrete structure with steel for tensile / shear strength.
Thanks for clearing that up.

I was wondering if rebar provided a stronger support structure better able to withstand lateral pressure cause the concrete goes through all the voids while I-Beam prevents concrete from 1 side connecting with concrete on the other side of the beam. Unless ofcourse you make holes in the beam but then you would have to strengthen the area around the hole either with additional metal or use flow drilling to make the holes. But then I figured if
I-Beam was inferior, the Americans who are experts in building high rises would not use it.

So is it purely a cost reason why Americans use I Beam and UAE uses rebar?I'm sure everyones seen pics from the early part of the 20th century where NY skyscrapers were being built with I Beam. I can certainly understand the cost issue, as my sis built a 3500 sqft house utilising traditional American wood framing and it cost just over $550,000. Labour (All Union labour) cost was the biggest chunk, which is probably why contractors opt for I-Beam over rebar, for commerical concrete structures.
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Old Dec 20th 2011, 2:47 pm
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Default Re: Construction related questions.

Originally Posted by Boomhauer View Post
Thanks for clearing that up.

I was wondering if rebar provided a stronger support structure better able to withstand lateral pressure cause the concrete goes through all the voids while I-Beam prevents concrete from 1 side connecting with concrete on the other side of the beam. Unless ofcourse you make holes in the beam but then you would have to strengthen the area around the hole either with additional metal or use flow drilling to make the holes. But then I figured if
I-Beam was inferior, the Americans who are experts in building high rises would not use it.

So is it purely a cost reason why Americans use I Beam and UAE uses rebar?I'm sure everyones seen pics from the early part of the 20th century where NY skyscrapers were being built with I Beam. I can certainly understand the cost issue, as my sis built a 3500 sqft house utilising traditional American wood framing and it cost just over $550,000. Labour (All Union labour) cost was the biggest chunk, which is probably why contractors opt for I-Beam over rebar, for commerical concrete structures.
I think you have to go back to Weasel's various posts about design selection-cost is invariably a factor, but rarely the only one. Ever wondered why some motorways in UK have flexible pavements (ie tarmac), and some rigid (ie concrete)? It is (or at least was, there may be other considerations now) to do with how far away the nearest source of either tarmac or concrete was, since the cost of transporting the material played a major part in determining the capital cost of the road. With dramatically-rising transportation costs, I imagine its still a factor.

(And before some of you start jumping up and down and saying that motorways don't have pavements, that's the correct terminology for the part of the road which vehicles run on. Pedestrians use footpaths.)
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Old Dec 20th 2011, 3:00 pm
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Default Re: Construction related questions.

So then, what is it for Christmas? Lego or Meccano?

Personally, while I love the engineering simplicity of Meccano, lego is just way cooler.
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Old Dec 20th 2011, 3:18 pm
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Default Re: Construction related questions.

Originally Posted by Millhouse View Post
So then, what is it for Christmas? Lego or Meccano?

Personally, while I love the engineering simplicity of Meccano, lego is just way cooler.
Meccano. In this day and age of PS2,Wi, Iphone and other electronic geewizardry, theres just something quite pleasing about turning bolts and screws.

Majic of Meccano. Theres also a link to a chap who built a difference engine out of Meccano.

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Old Dec 20th 2011, 3:32 pm
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Default Re: Construction related questions.

Originally Posted by Boomhauer View Post
Meccano. In this day and age of PS2,Wi, Iphone and other electronic geewizardry, theres just something quite pleasing about turning bolts and screws.

Majic of Meccano. Theres also a link to a chap who built a difference engine out of Meccano.
http://youtube.com/watch?v=FUN9H_e8aAw&feature=related
Cool. I do agree with you, but the issue I have with Meccano is the lack of locking nuts in the kits. As soon as you start playing with the stuff it all loosens and falls to bits.
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Old Dec 20th 2011, 3:39 pm
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Default Re: Construction related questions.

Originally Posted by Millhouse View Post
Cool. I do agree with you, but the issue I have with Meccano is the lack of locking nuts in the kits. As soon as you start playing with the stuff it all loosens and falls to bits.
Well you could use liquid threadlock , just depends on how much of a nuisance it is if you intend on breaking it down to build anew.
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