201 Extended Stay Suites
Chantilly, VA
David A. Klein
Structural Option
Master of Architectural Engineering Candidate
Advisor: Professor Thomas Boothby, Ph.D., P.E., R.A.
Structural Depth
An alternate structural design solution that has the potential to resolve the current design inefficiencies (see Revised Proposal below) is that of a complete slab redesign using post-tensioning tendons throughout. Utilizing post-tensioned slabs throughout the building will potentially allow the reduction of overall slab thickness and provide consistency to the slab thickness, reinforcement, and compressive stress rating. Post-tensioning the entire slab will also eliminate the need for post-tensioned transfer girders as the slabs will be able to span greater distances therefore eliminating the need for certain columns. Post-tensioning the slab would produce other benefits including an increased amount of open floor space on the lobby level.
Changing the current conventionally reinforced concrete slab system to a post-tensioned concrete slab system will also have an impact on the lateral system. Since the columns of the current system are engaged with the slab, they work in tandem with the concrete shear walls to resist lateral forces. If the final post-tensioned slab design involves the removal of columns, the size of the shear walls will have to be increase to withstand the higher associated loads. Aside from this possible change, the lateral force resisting system can potentially remain substantially the unchanged.
Mechanical Breadth
To complement the structural redesign described above, a mechanical system that limits vertical slab penetrations is preferred due to the addition of post-tensioning tendons. The current system involves individual fan coil units that are assigned to each individual guest room. The outside air is ducted in by rooftop air handling units and conditioned by a hydronic system supplied by rooftop air cooled chillers and rooftop boilers. The system study would consist of replacing the current hydronic fan coil system with packaged terminal air conditioner (PTAC) units of comparable capacity for each individual guest room. Both system effectiveness and cost of the alternate system would be analyzed in this study. The current hydronic system has limited slab penetrations as compared to that of a fully ducted system, however a system with even fewer penetrations can be achieved. A system that implements through-wall PTAC units would then eliminate a majority of slab penetrations due to HVAC equipment. The penetrations required for plumbing and electrical conduit will be optimized such not to interfere with critically reinforced slab areas such as column interfaces.
Lighting / Electrical Breadth
The current lighting design consists of florescent tube and compact florescent lamp lighting for the guest rooms and for a majority of the remaining spaces. A lighting / electrical design alternative for the current system is that of a fully LED lighting system for the guest rooms. To ensure that the alternate system performs equal or better than that of the current system, comparable LED luminaires will be chosen for both task and ambient lighting. Overall brightness, color temperature, and luminaire size will be considered in the final selection for the alternate lighting system. As part of this study, a system costs comparison will be performed to gain an understanding of the financial benefits of the alternate system versus the current system.