Mark Sarkisian, Partner, Skidmore, Owings & Merrill
David Shook, Structural Engineer, Skidmore, Owings & Merrill

Innovative planning for cities of the future is essential. Cities are the solution to responsible habitation as issues of the environment gain increasing importance. Even early at planning stages, cities, districts, parcels, and buildings can be evaluated for efficiency and environmental impacts. Design parameters such as site conditions, building height and form, structural system and materials, and anticipated construction time can be considered when evaluating design opportunities. Net useable space, specifically relating commercial value can be interactively considered based on anticipated service areas, structural systems and building shape. Considering only height limits and parcel sizes, the Parametric City Modeling™ can parametrically consider the impacts of building systems on net usable area, therefore efficiency / marketability of space. In addition, and perhaps most importantly, the algorithm can evaluate the environmental impact of these systems as well as the cost-benefits of enhanced system components over the development's service life.

Introduction

Designs for cities of the future need to be conceived by performance-based design. With decreasing material supplies and increasing demands, the cities of the future must use fewer natural resources while providing greater urban density and ultimately even the regeneration of resources. Decisions cognizant of the broader impacts on the environment and urban landscape need to be made early in the planning process through the conceptual design of districts, parcels, and buildings. Design must consider optimal net floor area efficiency, material use and resiliency to environmental disaster risks. Although efforts have been made at a broader level, little effort has been made to quantify performance at an individual parcel level. For example, municipalities can quantify fiscal and logistical impacts of increased height limits by allowing higher occupancy floor area ratios, but they do not account for potential limitations such as net usable area efficiency or embodied carbon. To quantify these and other metrics of future cities, advanced algorithms have been assembled and are used within Parametric City Modeling™ (PCM). Parameters including parcel size, building shape, building height as well as primary structural material and abnormal loading demands such as seismicity can be varied to understand their individual and collective impacts. With only the parcel size and height limit known, net usable floor area / commercial value and impacts on the environment (embodied carbon) can be evaluated. Key algorithms include:
  1. Building Systems Modeling (BSM): This algorithm calculates building systems floor area, anticipated lease spans, and net floor area given only a parcel's plan extent and height. Building systems modeled include core program, structural system, elevators, stairs, and MEP shafts.
  2. Environmental Analysis Tool™ (EA Tool): This algorithm computes embodied carbon associated with structural systems.
In the future other parameters such as shadow casting, day lighting, utility use such as water and electricity can be added with a weighting function to determine other optimal collective solutions.

With knowing only parcel sizes and height limits, PCM has been applied to the Transbay District of San Francisco, California, to evaluate net usable floor area and embodied carbon of structures. With a significant number of parcels being developed (Figure 1) the goal is to review impacts of the district as-planned as well as consider the impacts of taller height limits and variations of structural materials used for construction.

NBM&CW August 2015