highrise residential - concrete

huangyhg

highrise residential - concrete
please clarify this concept for me. why are modern residential highrise designed with concrete and not steel. i am particularly interested in knowing why we would see more modern steel commerial highrise and seldom residential steel highrise.
any explaination and clarifications would be appreciated. thanks
cost and the availability of source materials.
if you live in a place where there is a steel industry nearby then you'll go for steel, if there are lots of quarries then concrete.
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a major factor is story height. architects need it minimized, which flat plate concrete slab, pt or non-pt is at an advantage.
also think about fire-proofing cost.  for a steel building, you will have to pay for extra fireproofing materials between those steel beams and columns.  for residential structures, fire-rated materials must enclose each liveable unit, and it may be more economical to kill two birds with one stone: concrete continuous structural element + continuous fire-rated element.  
well... that was just an assumption, i really don't know if that is the only reason.
there are many considerations that go into selecting a steel or concrete structure.... bay size, loading, fire rating, code restrictions on height, material availability, labor market, costs and rates of inflation, architectural considerations, schedule, tenant contracts, etc.
an important consideration in making concrete competetive is that the structure must be repetitive (floor to floor heights and bay sizes) so that forms can be reused multiple times. formwork can be 50% of the structural cost.
generally, with concrete flat plates, lower floor to floor heights can be achieved which translates into savings in exterior skin, elevators and vertical mechanical runs. recently, the steel industry has been working with the precast market to develop steel products that are more competetive with concrete on floor to floor heights.