Flutter Derivatives Identification and Aerodynamic Performance of an Optimized Multibox Bridge Deck

Zhida Wang,Elena Dragomirescu

doi:10.1155/2016/8530154

Abstract

The bridge deck sections used for long-span suspension bridges have evolved through the years, from the compact box deck girders geometrical configurations to twin-box and three-box bridge decks sections. The latest generation of split and multiple-box bridge decks proved to have better aerodynamic behavior; thus further optimization methods are sought for such geometrical configurations. A new type of multibox bridge deck, consisting of four aerodynamically shaped deck boxes, two side decks for the traffic lanes and two middle decks for the railway traffic, connected between them by stabilizing beams, was tested in the wind tunnel for identifying the flutter derivatives and to verify the aerodynamic performance of the proposed multibox deck. Aerodynamic static force coefficients were measured for the multibox bridge deck model, scaled 1 : 80, for Reynolds numbers up to 5.1 × 105, under angles of attack between −8° and 8°. Iterative Least Squares (ILS) method was employed for identifying the flutter 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 flutter wind speed for the corresponding prototype of the multibox bridge was estimated at 188 m/s.

Highlights

After the failure of the of the first 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 ([1,2,3], etc.)
The curve of A∗1 derivative for multibox deck is very similar to the results reported for Messina Bridge deck section until a reduced wind speed of around 6.0 and gradually increases, locating between the Stonecutters and Messina Bridge decks
Except for small, H1∗, H2∗, A∗1, AH∗23∗, flutter and A∗3 derivative, which flutter derivatives was very registered values between the results reported for Messina Bridge triplebox deck and the Stonecutters Bridge twin-deck, indicating a very good aerodynamic performance for this new type of multibox bridge deck

Summary

Introduction

After the failure of the of the first 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 ([1,2,3], etc.). The aerodynamic stability criteria for suspension and cable-stayed bridges have been wellestablished ([4,5,6], etc.) and new challenges were raised in terms of the bridge deck geometrical configurations leading to the new generation of slotted bridge deck geometries ([7,8,9], etc.) with improved the aerodynamic performance, which allowed the development of longer bridge spans ([10, 11]) These new concepts of “synthetic” flutter control were discussed by Miyata [12] in an attempt to lower the flutter onset wind speed, which the Japanese design standards requirements set to 80 m/s, by proposing modifications of the deck cross section. The flutter performance of the proposed multideck bridge section was discussed with regard to the thin plate flutter theory and was compared with the flutter derivatives reported in the literature for other bridges with one, two, and three decks configurations

Experimental Setup for the Multibox Bridge Deck Model

Aerodynamic Response of the Multibox Bridge Deck Model

Flutter Analysis of the Multibox Bridge Deck Model

Findings

Conclusions