metal construction versus precast

[kuntay]

For industrial buildings with long spans (18-24 meters) which is more economical? Metal construction or preststressed precast concrete structures. What are the main advantages and disadvantages of these systems. Advice needed from experienced people. Thank you in advance.

 

[DaveAtkins]

Steel, being the strongest structural material readily available, should be more economical. One of steel's disadvantages is its flexibility, but this can be taken care of by using rigid frames and braced frames. Another disadvantage for steel is that it does not last very long when exposed to fire, but if this is not an issue for your project (i.e., you are using sprinklers, the building is not very large, there are not many occupants, etc.), then steel should be more economical.

DaveAtkins

 

[Ussuri]

Both steel suppliers and concrete suppliers will tell you their product is best. Steel is more economical in terms of its ability to span greater distances but it helps to define 'economical'. If by 'economical' you mean the standard engineering approach of using less material, however, in terms of programme steel may not as 'economical'.

Where I am base there is a lead in time for structural steelwork of about 15 weeks because of the current international market (a lot to do with China's massive industrial growth). Concrete on the other hand only has a lead in time of about four weeks. So your building might be finished 9 weeks early if made with concrete, and your client is earning revenue earlier. Which will put a big smile on their face, especially if its an oil refinery or a mall.

However, its not quite as simple as that because steel is faster to erect once on site. With concrete you also have to fix the rebar, which being steel might be as hard to get as structural steel. This is where the QS's make their money. But depending on size a concrete building might be finished before a steel one.

 

[civilperson]

In countries with high labor costs, the steel roof is most economical. In Mexico, Indonesia, Phillipines, etc. the concrete precast double tee will be most economical.

 

[SlideRuleEra]

I see your question from and Owner's viewpoint. For the industrial buildings at electric generating stations we "never" used precast/prestressed concrete framework - always steel. This was for several reasons:

1. Steel allows more offsite prefabrication which in turn allows faster onsite erection.

2. Hangers for field run piping, supports for for suspended electrical ductbanks, equipment access platforms, etc. can be easily welded to the steel, almost "as needed".

3. Since many industries are constantly upgrading and improving equipment and processes, steel is much easier to modify for the new loads. Also it is simpler to perform the engineering calculations for the the new loads on an existing steel structure than it is for an existing concrete structure.

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