Proposal for Redesign
1. Design Criteria.
a. Interior and exterior atmospheres should be improved via structural and lighting design.
Because the plan of the 750 East Pratt office tower is so dependent on that of the substation that it is built on, several basic architectural features beg improvement. The interior column grid is irregular, which is all the more noticeable in an open office plan. Because the anticipated scope of the project was smaller when the substation was constructed, the structural capacity of the substation allowed a height of only 10 stories over the northern part of the structure. Optimization of the structural system with consideration for the architecture of the building opens up several opportunities for improvement, including an inexpensive but dramatic increase in rentable space. Architecture must also be considered in the initial structural design and layout.
b. Structural design must be simplified and optimized through system redesign.
The main objective of this thesis project is to show how drastically the overall building structural system could be improved if the building were designed as one original project rather than as two separate projects. This can be accomplished by revamping the plan and reducing the necessity of transfer girders and connections wherever possible. Currently, the layout of the tower structural system is dependent on that of the existing substation, but the layout can be optimized to benefit the needs of both structures.
c. If possible, mechanical obstructions in structural members should be minimized.
Currently, the unusually large size and number of moment frames required to transfer lateral forces through the complicated structural system creates deep beams in inconvenient places. There are several instances where beams are penetrated by mechanical ducts, further increasing the size and weight of these members. This can most likely be avoided in redesign.
d. Floor-to-floor heights and plenum depth should remain consistent or be reduced.
Under no circumstances should plenum depth be increased as a result of this redesign. If this is an outcome of the design, one of several things must be sacrificed, including ceiling height, mechanical performance, or overall building height. All of these have negative consequences which should be avoided.
2. Structural Proposal.
The structural redesign of 750 East Pratt was first priority; however, consideration was given to each affected system in the building, and particularly to the architectural requirements. The new structural system must combine the needs of the BG&E electrical substation with those of the 15-story office tower above without overburdening either of them or using unnecessary measures to compensate one or the other. Designing this building as a unified system offers several opportunities: 1. the alteration of the column layout to optimize and enhance structural integrity, 2. the strengthening of the frame of the building to allow full utilization of the plan over 20 stories, and 3. the optimization of the lateral system to reduce material and labor costs. Redesign is contingent on all of these opportunities.
3. Architectural/Lighting Proposal.
The architectural redesign of 750 East Pratt is intended to supplement the structural improvements. The increased strength and symmetry of the structural system allowed the entire plan to support the full 20 stories of the building. If this is taken advantage of, it will inevitably alter the exterior appearance of the building. Because of the visible location and architectural importance of this particular building, consideration had to be given to the resulting impact on the view of approaching traffic on the freeway as well as pedestrians in the public space below. My goals were to preserve two concepts: 1. the integration between the low-rise industrial section (mimicked in the masonry clad electrical substation) and the high-rise commercial section (represented by the glass office tower) of Baltimore, and 2. the integration between the rectangular grid of the city to the East and the curved river to the West. Lighting of both the pedestrian space at night and the façade are critical to public safety and architectural appearance.
4. Other Considerations (Cost, HVAC).
A general cost analysis of the existing and proposed systems is necessary in order to fully gage the benefits of a unified design. Using takeoffs from RAM Frame and the original plans, the RS Means handbook, and information collected from AISC, a comparison and breakdown of the structural system materials costs of the building was conducted.
The additional rentable space allowed by the structural optimization of the north end of 750 East Pratt requires that mechanical loads be considered. A brief investigation was conducted to ensure that the increased roof area over this space could fit the additional chillers and cooling towers required for the added occupied volume.
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