Research Article Flutter Derivatives Identification and Aerodynamic Performance of an Optimized Multibox Bridge Deck Zhida Wang and Elena Dragomirescu Te University of Ottawa, 161 Louis Pasteur, Ottawa, ON, Canada K1N 6N5 Correspondence should be addressed to Elena Dragomirescu; elndrag@uottawa.ca Received 12 March 2016; Accepted 26 July 2016 Academic Editor: Ghassan Chehab Copyright © 2016 Z. Wang and E. Dragomirescu. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te bridge deck sections used for long-span suspension bridges have evolved through the years, from the compact box deck girders geometrical confgurations to twin-box and three-box bridge decks sections. Te latest generation of split and multiple- box bridge decks proved to have better aerodynamic behavior; thus further optimization methods are sought for such geometrical confgurations. A new type of multibox bridge deck, consisting of four aerodynamically shaped deck boxes, two side decks for the trafc lanes and two middle decks for the railway trafc, connected between them by stabilizing beams, was tested in the wind tunnel for identifying the futter derivatives and to verify the aerodynamic performance of the proposed multibox deck. Aerodynamic static force coefcients were measured for the multibox bridge deck model, scaled 1 : 80, for Reynolds numbers up to 5.1 × 10 5 , under angles of attack between −8 ∘ and 8 ∘ . Iterative Least Squares (ILS) method was employed for identifying the futter derivatives of the multibox bridge deck model, based on the results obtained from the free vibration tests and based on the frequency analysis the critical futter wind speed for the corresponding prototype of the multibox bridge was estimated at 188 m/s. 1. Introduction Afer the failure of the of the frst Tacoma Narrow Bridge at half of its design wind speed, bridge which was designed to withstand static wind load only, various methods have been adopted for analyzing the aerodynamic instability of long-span bridges, with the assistance of wind tunnel tests ([1–3], etc.). Nowadays, the aerodynamic stability criteria for suspension and cable-stayed bridges have been well- established ([4–6], etc.) and new challenges were raised in terms of the bridge deck geometrical confgurations leading to the new generation of slotted bridge deck geometries ([7–9], etc.) with improved the aerodynamic performance, which allowed the development of longer bridge spans ([10, 11]). Tese new concepts of “synthetic” futter control were discussed by Miyata [12] in an attempt to lower the futter onset wind speed, which the Japanese design standards requirements set to 80 m/s, by proposing modifcations of the deck cross section. Te “spindle-type” bridge deck he proposed had the deck divided into two symmetric box decks on the main span only, while on the lateral spans a conventional closed box deck was used; however the critical futter modes proved to be asymmetric for the main span and symmetric for the side spans. Several twin-box deck bridges have been constructed recently, such as Stonecutters Bridge of 1,377m main span [13], Tsing Ma Bridge with main span of 1,650 m [14], and Xihoumen Bridge of 1,410 m main span [11], and three-box bridge decks have also been designed for Messina Bridge [7, 15], Gibraltar Strait Bridge [16], and Sunda Strait Bridge [17]; however none of these bridges were constructed yet. In order to investigate the impact of diferent deck cross-sectional confgurations for bridges with torsional to vertical frequencies ratio lower than unity, on the aerodynamic stability, but also on the cost reductions, implied by the construction solution, Bartoli et al. [18] analyzed several deck cross sections using the same width and then increased width with regard to the reference Messina Bridge, but eliminating the middle deck. Also most of the mass of Hindawi Publishing Corporation Advances in Civil Engineering Volume 2016, Article ID 8530154, 13 pages http://dx.doi.org/10.1155/2016/8530154