A Structure for the Next Century
|Project Brief:||Design an element (system, component, building, etc.) of a sustainable city block.|
|Concept:||A system of modular concrete jack arches and a curtainwall facade forms an approach that is durable, flexible, sustainable, honest, enjoyable, and appropriate for mid-rise urban development.|
|Team:||Carl S. Sterner, Lyle Solla-Yates|
An approach to mid-rise construction that is flexible, durable, honest, sustainable, and sensuous.
The challenge: design an integral piece of a sustainable city block. We focused on designing a structural system that is durable, flexible, cost effective, and lends itself to sustainable and pedestrian-friendly design.
Buildings have several layers, each of which change at different rates over time. In medium- to high-density construction, the structure is the most durable and should be built to last and to accommodate a variety of future uses. Moving away from the structure, each successive layer is less durable and needs to be more flexible, allowing design for disassembly and simple reconfiguration by users. Buildings need good bones and flexible facades and interiors. This structure, made of concrete jack arches, is ideal for its durability and ability to accommodate changing needs.
To test its adaptability, we designed three buildings using this system. One, pictured in slide #1 above, was designed for a site in Roanoke, Virginia, as part of the Build District Roanoke project.
- Solar battery: Concrete's thermal mass is ideal for passive solar heating & cooling.
- Carbon sink: The use of fly ash or slag in concrete can reduce its carbon footprint while diverting industrial waste that would otherwise be landfilled. New technology, such as the use of magnesium silicate-based cement that absorbs carbon as it hardens, can actually make concrete carbon negative.
- Density: Concrete is appropriate for multi-story buildings, providing sufficient density to support transit and walkable communities (together with surrounding buildings).
- Extra strength: The structure is strong enough to accommodate future expansion, the addition of green roofs, etc. The use of fly ash and slag can also increase the strength of concrete.
- Durable: Concrete that is sealed properly and well-maintained can last millennia, making design for disassembly unnecessary, favoring design for adaptability.
Why jack arches?
- Efficiency: Arches take advantage of concrete's natural compressive strength, and therefore require less concrete and less steel than conventional concrete construction.
- Less steel: Steel prices are high and rising. Most structural steel is recycled, but still comes at a high energy and environmental cost. Using rebar in concrete can reduce concrete's life span by causing spalling and cracking. This design conserves steel.
- Delight: Jack arches are structurally honest, simple, elegant, and engaging to the eye and hand. Delight is important for durability: buildings survive because people love them.
- Appropriate technology: Concrete jack arches can be prefabricated off-site or made by hand on-site, depending on whether resource cost or labor cost is the driving factor.
Other design features:
- Flexible spaces: High ceilings, long spans, and large windows create a space attractive for nearly any use, extending building life. These conditions also provide excellent daylight and opportunities for views and natural ventilation.
- Flexible systems: Mechanical systems can be underfloor, where they are easily accessed and can be controlled by the user, or within more traditional dropped ceilings.
- Flexible façades: This structure can accommodate nearly any modern façade, which can be designed for disassembly and reuse.
- Off-the-shelf: This design can be achieved now, with existing technology.
To test its adaptability, we designed three buildings using this structural system. Each example is on a different site, and utilizes a different type of façade. Each responds to context and solar orientation, and creates a pedestrian-friendly urban experience.