In the high rise buildings in the ,why the still use the reinforced concrete with huge amount of steel rebars instead of using the composite sections?

Normally low to medium rise buildings are desigined for gravity loads, then checked for their ability to resist lateral loads. However high rise buildings are mush more susceptible to lateral forces action, therefore the amount of materials needed for resistance of lateral forces increases at a drastically accelerating rate.

Therefore in the high rise buildings still use the reinforced concrete with huge amount of steel rebars, instead of using the composite sections.

Prepare a Base Plot form , place the steel and cover steel with water proof material

Research papers indicates that about more than fifteen storied building are economical when they are constructed composite. Off course ductility of the structure is enhance in composite construction there by enhancement in dynamic load carrying capacity. Compared to pure steel construction, more economical and less transverse movement or sway.But design standards like Euro code four are to be revised and more researches has to be done. For example, instabilities in columns like buckling, imperfections etc. I did study on this. I can give you a report.

Because you need stiffnes in a building , especialy in high Rise. Also it is  thought is that its better fire protected, but it still keeps you from a quick building time.

Think in steel, works quicker and for fire protection you have cladding, sprayconcrete or sprinkler.

But is steel rebar the only rebar? Now we have basaltfibre rebar.

Depending on the design, don't only think in concrete . allways search for alternatives

 

Reinforced concrete along with steel rebars are still highly preferred due to the excessive need to lateral forces resistance, especially in high rise buildings.

 

 

 

in my openion,using the composite section can be more econimical that the normal rebars since we reduce the concrete size and also we reducing the steel it self.

It is purely a design oriented decision. The resultant tensile forces and moments due to critical load factors, (wind, EQ etc) is the criteria for the selection of quantum of steel as a tensile material. 

The developed composite sections or the alloys invented to take care of the forces developed in the high rise structures and in compatibility with the concrete, if available, should not be a concern.

Dear Mr. Mohamad , the composite sections can be used in high rise buildings , but most of theses buildings found in rich counties and good economic enviroment whom no need for think about cost.