The Summit at
Drexel University
Structural Description
The new Summit building is comprised of five major parts: the tower, retail space, dining space, lower level and mezzanine level, and parking garage. The tower is easily the largest component of the structure, rising 278 feet in the air and holding all 351 residential units. The majority of the structure was built with structural, reinforced concrete with the exception of the top two penthouse floors, the dining space, and the mezzanine level of the retail space, which is structural steel frame.
The envelope of the building consists of a combination of pre-cast concrete and glass panels. The glass paneling covers the majority of two sides of the building, mainly on the residential tower, while the precast concrete surrounds the other sides as well as the entire perimeter of the lower level.
Design Selection Reasoning
The design selection for Summit's structure was chosen for a variety of structural, economical, and time sensitive reasons. The concrete structure, while very heavy, is quick and cheap to build in relation to its strength and longevity. It was also mentioned by Hunter Roberts that it was the cheapest material during the design stage of construction. It is also one of the better options for sound insulation in buildings which is an important factor when designing residential apartments.
The top two floors of the tower are built with structural steel which lowers the overall dead load on the rest of the structure. These two floors house a majority of the HVAC and elevator mechanical equipment. Therefore, the smaller column widths allow wider bays for equipment.
Foundation Description
The theme throughout the building structure has been two blend two strong components together to produce an even more efficient result. This holds true for the foundations as well. The design team decided to combine the use of caissons and spread footings beneath the building to achieve a strong and sturdy base. The entire 24 story tower and lower level are supported by approximately 100 caissons driven into the ground. The caissons vary in size, the largest being 8 feet in diameter and 50 feet deep. The parking lot, however, carries much less of a load than other parts of the building, so it is completely supported by spread footings. The final area of the building, the dining area is supported by a combination of spread footings and caissons.
Possible Improvements
The structure of a building does not tend to be a component that can be improved very easily. Once the construction is underway it is hard to modify the structure without putting the entire project at risk. However, there are a few beneficial alternatives to what the design team finalized. Instead of choosing concrete, a standard steel or diagrid frame could have been chosen. This would have lightened the load of the entire building being transferred to the foundations, which may have minimized the amount of caissons needed to support the building. A diagrid system would also improve the aesthetics of the building possibly resulting in a higher demand in residency. However, a major drawback of the steel frame is cost. It would cost significantly more than concrete which was not a desire of the owner. The dinig area already has an architectural diagrid facade, but continuing this through the entire building would really enhance the appearance.
Lower Level Foundation Plan
The envelope of the structure was designed with weight in mind. The initial plan to completely surround the building in pre-cast concrete was rejected due to a possible weight restriction. This was when the glass curtain wall-like component was suggested. It is much lighter than pre-cast, however designers thought that the finished structure would look too much like an office building with an entire glass facade. Instead, they decided to cover the building with a combination of pre-cast concrete and glass panels to enhance the view from each unit and overall aesthetics of the building but still maintain the integrity of the residential structure.
Tower Column Plan
View of architectural diagrid system.