Cast-in-place concrete structures are very common, with their high strength and stiffness, resulting in very sturdy and rigid buildings, and the material cost per unit is fairly low as well. However, because of concretes properties, a large amount of it is needed to obtain the strength needed for the loadings it will see, as well as the skilled labor to construct a building out of it. Post tensioning introduces yet another prohibitive cost addition in the form of extra equipment and the skilled labor to construct it properly. So what could be done about this?

 

            From the alternative systems investigation, a promising design would be to construct this building using composite steel framing. Switching to a steel structure instead of a concrete structure would result in the building overall being lighter, thus lessening the total load. The thick concrete columns that currently exist could be drastically reduced in size if designed as steel columns, and steel can easily span the same lengths, and even allow for less columns and a more open floor plan. However, the spans in the redesign should remain the same, as it was found in the alternative systems report that the girders would be fairly deep as is. With switching to a lighter floor system, vibration control has to be considered, and this will be part of the redesign to make sure that there is no vibrational issues that would cause issues with the occupants. Making sure that a steel structure would also allow as many levels in the building as the original design, since the overall floor thickness would increase, will also be investigated to make sure that the same floor space can be retained while making the building lighter and more open.