Apr 15 2004
A proposal for developing a composite floor system incorporating structural steel and aerated concrete earned a $10,000 prize from the American Institute of Steel Construction, Inc. in a recent competition to develop innovative systems for multi-story residential construction.
The system, proposed by Keith Itzler of Dewberry-Goodkind, Inc. in New York City, is a relatively simple combination of structural steel, a tried and true construction material, and autoclaved aerated concrete (AAC), also a proven construction material. Composite action between concrete and steel is a well-established structural principle, which should be fully applicable to the combination of steel and AAC. The system proposed has a high potential for development, meets the evaluation criteria and should be beneficial to promoting the use of both steel and AAC in multi-story residential buildings.
A $5,000 second prize was awarded to Patrick M. Hasset, S.E., of Hassett Engineering in Castro Valley, CA, for his proposal for a “stiffened plate floor deck.” The proposed system utilizes a relatively thin deck plate stiffened by “closed” ribs similar to a deck system used in orthotropic steel bridge decks. Unlike bridge construction, this “Stiffened Plate Floor Deck” (SPFD) does not require fracture critical steel, and high quality control welding since the deck design is controlled primarily by deflection criteria.
“Multi-story residential is one of the fastest growing segments of the construction industry,” explained Tom Schlafly, AISC’s Director of Research. “Traditionally, much of this construction has utilized pre-cast concrete, in large part due to the desire of developers to minimize floor-to-floor heights. Recently, several steel systems have been gaining acceptance, including Girder-Slab, staggered truss, stub girder, and precast plank construction. However, additional innovative steel systems are still needed to support AISC’s mission of making structural steel the material of choice for construction.”
The competition was the second part of a project to create innovation in the design and construction of steel multi-story residential projects. For the first stage, AISC funded a four-year Faculty Fellowship Award, which was presented to Amit H. Varma, Ph.D., of Michigan State University. Varma is working on the development of innovative long-span floor systems for multi-story residential applications. The project includes the conceptualization, development, detailed analysis, design, and experimental evaluation of several candidates for long-span floor systems. Several performance criteria including behavior for construction loads, service loads, ultimate loads, fire resistance, and floor vibration are being optimized.
The second part was the competition won by Itzler and Hassett, which brought entries from architects, students, builders, inventors, and engineers. “The competition was an opportunity for applicants to develop and submit an idea that would be evaluated by peers and promoted to colleagues--without the need to conduct major research on their own,” explained Varma who—as part of his fellowship project—will further investigate the winning concepts.
A panel of consultants and contractors judged the contest submissions. The evaluation criteria included economic viability, contribution to the goal in terms of useful span and system depth, constructability, serviceability and durability. Submissions included a variety of innovative concepts. For example: innovative framing schemes to help achieve the minimum floor-to-floor height requirements in residential construction, use of new and innovative materials to provide lighter and shallower floor systems, combination of newer and traditional construction materials to develop effective floor systems, structurally efficient floor systems fabricated using traditional hot-rolled and cold-formed structural shapes, and use of prestressing to provide additional stiffness and reduce the depth of the floor system.
Source: AISC