For the structure of the building, the engineer could have chosen from a multitude of design options:

• Steel frame

• Diagrid 

• Cast-in-place concrete

• Precast concrete

• Wood

• Bearing wall structure 

 

After looking at the structural options available, steel and concrete frames made the most sense. A diagrid structure would have been too expensive; a wood structure would not have been able to carry the loads of the structure; and a bearing wall structure would have needed very large walls on the bottom levels in order to carry the loads, which would occupy rentable space and would affect the look of the glass exterior as well. Steel and concrete frames are simple and cheap and are both capable of handling the loads that are produced within the structure.

 

The final decision to go with concrete was made mainly because the designer was given a very cheap price quote for cast-in-place concrete. Cast-in-place concrete is also a good selection because concrete can handle high compressive loads and is fire-proof without any extra costs. Steel on the other hand, is cheap but requires fire-proofing,which is an added expense. However, there was steel framing used at the top of the building in order to make the top of the building lighter in weight and quicker to erect. The concrete frame also allowed for the facade of the building to be non-load bearing, which supported the architect’s desire for the facade to be a composition of glass and concrete panels.

Cast-in-place concrete was the best choice in our opinion, however, an improvement could have been made to the structural timeline of the project. The project began in September knowing that the structure was to be constructed with cast-in-place concrete. This meant that the project was scheduled during the coldest months of the year. Concrete does not cure when the temperature outside is too cold and this caused delays in the schedule. If the building would have started earlier in the year, the weather would have been warmer, and the concrete would not have caused delays.