Module 6 - Evaluate Your Alternatives

Image of My Model

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Image of Your Results

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Description

Before even applying my evaluation scheme, I noticed that one of my nine cases did not meet the maximum floor area requirement given it had a floor area of 1,521,086 sf which is above the maximum permissible of 1,500,000 sf. I decided to create my evaluation scheme on Excel in order to easily filter out this case but importantly to work in a visual environment where I could see all cases and parameters in a single table. I used an importance weight ranking system whereby I set the importance of each variable on a scale of 0-5. I allocated a ranking of 5 to cumulative solar insolation and floor area because these largely drive revenue streams and operational costs. San Francisco largely having a gloomy microclimate compared to other Bay Areas, solar insolation is even more attractive. Solar insolation can also allow heat penetration in the winter months, reducing the heating load. Most towers lease spaces on a per square foot basis which is why thinking from the perspective of a building owner/developer I ranked this 5. I ranked surface area a 3, given that for most buildings, the surface area does not tend to be a design driver in itself, rather other factors which may be connected to this such as views, thermal performance, lighting etc. however developers do not usually think of surface area target when regarding a new development. Lastly, I set construction cost at 4, as this is an important consideration in even seeing whether we can afford to construct the tower, however I did not give this an importance of 5 given how a factor such as solar insolation can lead to operational cost savings throughout the life of the building, cost savings which may be more attractive than the savings based on initial construction cost.

For each of the variables I was using to choose the best alternative, I first normalized rankings using interpolation to values between 0-1 with 0 being least favorable and 1 being most favorable. This required reversing the ranking for construction cost and building surface area as we wanted to optimize for lower values for these categories. Once these were calculated I then amplified them using the weighting system, before individually summing the rankings of each test case. From the results, I noticed that the best cases were on the taller end of the spectrum but also with less rotation of the tower at mid-height. My best choice for the building was case 7 which has a height of 750 ft and a mid-height rotation of 30 degrees. Apart from being the best case with the weighting system applied, this case is also more plausible from a constructibility point of view by twisting less which would reduce the complexity of construction and cost of fabricating largely custom building elements.