Structural Proposal: Alternative Systems

After careful consideration of multiple alternative gravity systems in Notebook B, the simplicity of the structure and fabrication makes either a steel non-composite or a traditional composite beam system the clear alternative design for the gravity system in One on Centre. This system will not increase the floor to floor height or change the architecture in the structure as there are already girders with a similar depth that will be needed to carry conventional steel shape infill beams. The use of this alternative system has the potential to change the weight of the entire building and may result in the redesign of columns in the building. A further analysis will be completed to determine whether a non-composite or composite is the best gravity system after a comparison of the new system to the existing.

 

Notebook C encompassed a structural analysis of the existing lateral system in the building and questioned whether the existing shear wall system could potentially benefit from additional lateral support at the end of the “L” shape on the south facing wing. Doing so would add support to the structure and yield desirable results for drift, sway, and stiffness for the building. A “flexibility” analysis for the movement in the end will be completed to determine if one of three systems need to be researched further or if the fourth option needs to be considered. A feasibility study of these three different systems, described below, will be done in the event that it is determined that additional lateral support is needed. The first option is a braced frame system which will dramatically reduce story drift as well as axial forces and bending moments in columns. This method is very economical, easy to erect, and doesn’t occupy a lot of space. The second option is a moment frame system. This system can be expensive and will most likely not be feasible due to the height of the building. The third option is to add another shear wall at the end of the ‘L” shape, therefore improving the current system in areas where it currently may not be performing on par with the rest of the structure. The fourth option is to be explored in the case that the flexibility analysis comes back with results yielding that the displacement at the top of the building as well as the allowable story drift ratio are both within allowance determined by the height of the building. If this is the case, it will be determined if the structure is overdesigned, and possibilities of reduction of the current system will be explored.

 

 

Breadth Topic 1: Acoustics

The acoustical breadth for One on Centre is to determine the current reverberation time for the retail space. The space under examination is in the North-East segment of the building and is a 3 story, 23’ retail space. The retail area is constructed from three main elements, a curtain wall system, steel members, and concrete. The only sound suppressing element in the space currently is gypsum wallboard. The designation of “retail” for the space makes the room rather open-ended to how it will be used which is a cause for concern to how sound will reflect off the different elements in the area potentially making it worse. Based on a preliminary analysis of the space and a volume of 50,300 cubic feet, the reverberation time is 2.14 seconds. This exceeds standard reverberation time for every category except a concert hall. Therefore, sound suppressing panels may be used or other sound suppressing elements to keep the space from exceeding acoustical reverberation time standards. Further calculations will need to be completed to determine what the acoustical opportunities there are to improve the space and what options are the most efficient and cost-effective.

 

 

Breadth Topic 2: Mechanical Duct Sizing

One on Centre’s typical bays are originally constructed from open web joists between w-shape beams. These open web joists allow for ductwork to pass through and be distributed throughout the building. By changing the building to all solid web infill beams this will cause the ducts to be run in a different path as they will need to go under the structural members for the length of the new run. The new ceiling cavity dimension will need to be determined for the maximum duct height and widths will vary accordingly.  These ducts will be resized if necessary to fit the needs of the upper levels in the residential space in accordance with ASHRAE 62.1 for ventilation using a ductulator. If resizing is needed for a run, the proper air flow (cfm) and friction (head) loss will be taken into consideration to properly size a new duct to fit the space without creating vibrations and noise disturbances. The depth added to the system from the ductwork being run under the structural members rather than through them will be considered for the overall depth of the new structural system. Floor to floor heights with this new design may be greater than the current design, but if necessary will minimally alter the façade of the building. In areas where the duct work cannot be run under the structural member, the floorplan will be altered to accommodate the HVAC equipment to ensure a proper fit under the structural system as to not increase floor to floor height.