FLEXIBILITY IN DESIGN - Title Page - MIT
FLEXIBILITY IN DESIGN - Title Page - MIT FLEXIBILITY IN DESIGN - Title Page - MIT
de Neufville + Scholtes D R A F T September 30, 2009Box 1.4_____________________________________________________________________________Flexible design: Tagus River BridgeThe Ponte de 25 Abril, the first bridge over the Tagus River at Lisbon, offers a good example offlexibility in design. The Salazar dictatorship inaugurated it in 1966 with a single deck forautomobile traffic, but with the strength to add on a second deck at some future time. Moreover,they also built a railroad station under the toll plaza, to minimize disruption in case Portugal everdecided to build rail connections.A generation later, Portugal was a democratic member of the European Union, whichallocated funds to develop commuter rail services throughout the region, and in 1999 the bridgereceived a second deck that carried these lines. 5When first built, designers recognized that the ultimate capacity of the bridge could belarger. Instead of trying to anticipate specific future requirements, they built for immediate use,with the flexibility to develop in many ways. In any case, if the original designers had tried todefine future requirements, they could hardly have imagined the overthrow of the dictatorship andthe creation of the European Union.The flexible design of the bridge saved money by not building too early or building morehighway capacity that might have been inappropriate. It also enabled Portugal to take advantageof the support of the European Union to create rail traffic across the river._____________________________________________________________________________Box 1.5_____________________________________________________________________________Flexibility leads to major gains: satellite fleetA detailed analysis of alternative ways to deploy geostationary satellites over different regionsshowed that a flexible system design, that enabled the system operators to reposition thesatellites as demand for broadcast services changed, greatly outperformed the system“optimized” for the specified “most likely” pattern of demand. 6As Table 1.2 shows, the flexible design increases the overall expected value. Instead oflaunching the final fleet right away, it initially launches a smaller fleet – this simultaneouslyreduces the amount initial capital expenditure, thus the amount at risk and possible losses. Theflexible design then deploys the second module sized and located according to actual need,thereby obtaining a maximum value if the demand exceeds original anticipations.[Table 1.2 here]_____________________________________________________________________________Part 1: Chapters 1 to 3 Page 14 of 69
de Neufville + Scholtes D R A F T September 30, 2009Box 1.6_____________________________________________________________________________Application of 4-step process: high-rise buildingMany developers have used “vertical flexibility” in the design of their buildings. The developmentof the Health Care Service Corporation building in Chicago illustrates the process. 7 The originaldesign for this building has the strength, the space for elevator shafts and stairs, and the planningpermissions to add 24 more stories to the original 30-story skyscraper built in the 1990s.The 4-Step Process proceeds as follows:1. The architects/developers recognize client’s uncertainty about the amount of space needed,for example because it is not possible to be sure about either the long-term growth or howzoning regulations might change to allow them greater height.2. They identify that vertical flexibility is the only realistic possibility, because they cannotincrease the area available for development.3. They explore numerous design alternatives, involving different numbers of floors for the firstand later possible additions; estimate how each might perform under the range of futurescenarios; and choose the arrangement that provides the overall best set of metrics.4. They plan for implementation by making arrangements with the multiple stakeholdersinvolved in the execution of the vertical flexibility, and monitoring developments to determinewhen (and if) they should use their design flexibility. They obtain planning permission forexpansion, operational support from the tenants, financial commitments from the bankers, etc.They then keep track of their needs for additional space. The owners inaugurated theadditional phase in 2010.[Figure 1.3 here]_____________________________________________________________________________Part 1: Chapters 1 to 3 Page 15 of 69
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de Neufville + Scholtes D R A F T September 30, 2009Box 1.6_____________________________________________________________________________Application of 4-step process: high-rise buildingMany developers have used “vertical flexibility” in the design of their buildings. The developmentof the Health Care Service Corporation building in Chicago illustrates the process. 7 The originaldesign for this building has the strength, the space for elevator shafts and stairs, and the planningpermissions to add 24 more stories to the original 30-story skyscraper built in the 1990s.The 4-Step Process proceeds as follows:1. The architects/developers recognize client’s uncertainty about the amount of space needed,for example because it is not possible to be sure about either the long-term growth or howzoning regulations might change to allow them greater height.2. They identify that vertical flexibility is the only realistic possibility, because they cannotincrease the area available for development.3. They explore numerous design alternatives, involving different numbers of floors for the firstand later possible additions; estimate how each might perform under the range of futurescenarios; and choose the arrangement that provides the overall best set of metrics.4. They plan for implementation by making arrangements with the multiple stakeholdersinvolved in the execution of the vertical flexibility, and monitoring developments to determinewhen (and if) they should use their design flexibility. They obtain planning permission forexpansion, operational support from the tenants, financial commitments from the bankers, etc.They then keep track of their needs for additional space. The owners inaugurated theadditional phase in 2010.[Figure 1.3 here]_____________________________________________________________________________Part 1: Chapters 1 to 3 <strong>Page</strong> 15 of 69
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