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Form-finding and Optimization of Stability-Sensitive Footbridges

Speaker: Allison Halpern, Graduate Student
Series: MMS Brown Bag Seminars
Location: Engineering Quad E219
Date/Time: Tuesday, November 5, 2013, 12:30 p.m. - 2:00 p.m.

Abstract:

In traditional applications of computational form-finding to footbridge design, the shape of the bridge deck is predefined and the railing is ignored. Designation of the railing as a load-carrying component via integration with the bridge deck allows for both elements to be incorporated into a form-finding routine. As the deck must be easily traversable, its maximum slope is defined by accessibility guidelines, a constraint that limits the form-found deck to a shallow, funicular arch, which is susceptible to buckling. With the primary compression load path travelling through the top chord of the railing, the lack of lateral stability poses an out-of-plane buckling problem.

While form-finding methods allow for the generation of a structurally efficient form under gravity loads, optimization methods can be employed to arrive at a structural design that provides increased resistance to buckling and live loads. With the longitudinal profile of the footbridge deck constrained by accessibility guidelines, the railing geometry can be utilized to improve the stability performance of the structure under multiple loading conditions. This seminar presents a framework for utilizing form-finding algorithms, optimization techniques, and linear & nonlinear buckling analyses during the conceptual design phase to produce footbridge designs with improved structural performance.