Flutter stabilization of long-span bridges by means of wings and improving these wings considering conventional wing design

It is obvious fact that the cable-supported bridges, including both cablestayed bridges and suspension bridges, are choosen more day by day around the world because of their sufficiency for long spans. Even though they let the engineers to span long distances, this type of long span birdges are known generally remarkably flexible, in terms of damping is low efficient and in the sense of weight is light. Thus, these long-span cable supported bridges can also be susceptible to wind effects. The oscilation of the long-span bridges and aerodynamic stability of cable-stayed bridges are one of the major concern in bridge engineering. For example, the Tacoma Narrows suspension bridge, which had a main span of 853m and was built to link the Olympic Peninsula with the rest of the state of Washington, oscillated through large displacements at a wind speed of about 19 m/s and collapsed on November 7, 1940, only four months and six days after the bridge was opened to the public. As compared to other types of bridges, long-span cable-supported bridges are remarkably flexible. Since cable-stayed bridges are extremely slender, unexpected results of the wing effects on these bridges and aerodynamic problems in cable-supported bridges led engineers to concern about wind effects. Although cable-stayed bridges have been found surprisingly stable aerodynamically, several bridges have required special improvement against wind action on bridges. The different engineering branches have in common to improve engineering problems through their perspective and people from around the world labor to contribute technical progress in their related field. Not only in the scientific field, but also in practice, research to optimize issues and to figure out the new solutions to relevant questions. Due to its delicate construction, suspension bridges brings specific problems with the need to be considered already in the design. One of these problems is the wind generated flutter, a problem of stability for the suspension bridges is particularly vulnerable. A wind load is a highly unsteady operation. At the critical wind speed known as the air forces act in resonance with the bridge and lead to the steady growth of the amplitudes. This swings the bridge with the flutter natural frequency, which is always located between the rotational natural frequency and the natural bending frequency. Flutter occurs only when the rotational natural frequency is above the natural frequency of the bending vibration. At very low and very high frequency ratios flapping is prevented or impeded. In the previous studies, it was found found ways to stabilaze this oscillation such as increasing the rotational stiffness and forming the deck shape as aerodynamic body. An increase in the difference between the first bending frequency and the first rotational natural frequency has a favorable effect on the critical wind speed. Improving the deck section from conventional form to the aerodynamic shape is one of these studies which was carried out in practical field. This new method has been already studied and the necessary prior arrangments has been identified in former master subject. The former subject was investigated to increase the flutter resistance of long-span bridges. The resulting air forces there are means of one or both sides attached wing structure contributing to raising the critical wind speed of the overall system. The wings were only intended to contribute to stability and flutter not participating in the load transfer. They were not used as a roadway or sidewalk, but should be able to be manufactured and installed as low as possible. Furthermore, they should have been as light as possible and not interfere with the overall aesthetics of the bridge. In this work, considering these ideas and the knowledge which mentioned above, it has been intended to improve the attached wing structures from the previous plate-like wing structure to symmetric elliptic airfoil sectioned wing structure by using conventional wing design.