2 Units
- Seismic Loads on FDN
- Design Variables
- Seismic Overturning Moment = Floor Heights * Floor Weights * Floor Areas * Acceleration Demand
- In this case, I will evaluate for unitary floor weights and unitary acceleration demands. I will also assume a uniform distribution of lateral loads.
- Evaluators
- Seismic Overturning Moments Potential = Floor Heights * Floor Areas
- Most Important Tradeoffs to Consider
- Large Seismic Overturning Moments are highly undesirable. If we have a Pile FDN, we will require deeper and bigger piles in order to accommodate these loads which becomes very expensive and time consuming very quickly. However, taller buildings will accommodate more floor area, which means more money. There is a practical limit on this, which I wish to explore on this assignment.
- Net Present Value
- Design Variables
- Cost at Base Floor
- Cost Increase per Additional Floor
- Rent Price at Base Floor
- Discount Rate
- Discount Period
- Evaluators
- No project has ever started with a projected negative cashflow. It is important to calculate a net present value given the projected initial investment and an expected payment. In this case, the payment is in the form of an annuity, similar to bond payments.
- Most Important Tradeoffs to Consider
- Taller buildings will be more expensive to build. However, it is more desirable to live in an upper floor and people are willing to pay for it. In addition, one must do a sensitivity analysis to see how vulnerable the project is to changes in the discount rate (specially for high inflation periods like the current one).
- Surface Area / Volume
- Design Variables
- Heights
- Areas
- Proportions
- Evaluators
- Surface Area / Volume
- Most Important Tradeoffs to Consider
- This evaluator is related to energy efficiency in buildings (and many more things in real life). The smaller this ratio, the easier it will be to thermoregulate our building.
Square towers are so 1900s. For this example, we have a tower with an ellipse cross section with different radiuses proportions that contracts at a certain height by the user. In this case, we will vary the proportions of the ellipses and the number of floors in the structure in order to maximize the Net Present Value and minimize the Seismic Overturning Moment Potential.
We can observe that Net Present Value (Y-Axis) seems to reach a limit while the Seismic Overturning Moment Potential keeps increasing. This is given an increase in the number of floors while the R2/R1 proportion seems to stabilize. In early stages of design, soil properties are one of the few variables we may know, and we may want to limit loads on foundation systems given the type of soil profile. As we can see, the results follow to lines (yellow and orange). In the yellow line, our increase in NPN is linear with the Seismic Overturning Moment. In the orange lines, this has a lower slope which means that while we increase the risk of high FDN loads and Soil Collapse, our return in investment is diminished. Given our risk tolerance, we will take a design decision.
