Some Wind-Resistant Performance Of FRP Cable-Stayed Bridges

Since the beginning of the 21st century, the construction of bridges in China has entered an era of rapid developments that the spans of cable-stayed bridges and suspension bridges have both rewritten the span records. However, numerous bridges, still in their service stage, are suffered from serious corrosion and fatigue problems. It is these problems that threaten the structural durability and service life and bring new challenges to the bridge designers. Recently, FRP materials have gained increasing attentions from the engineers due to their extraordinary material properties, such as corrosion immune, fatigue resistant characteristics, lightweight and high strength.In this dissertation, a three-span FRP cable-stayed bridge system with FRP main girder and cables is proposed. For economic reasons, the bridge towers adopts the traditional materials—the reinforced concrete. Relatively systematic investigations of the FRP bridge deck system and wind-resistance performances of FRP cable-stayed bridges are carried out. The main works in this paper are as follows:1. A FRP bridge deck is proposed, and based on this deck, a FRP streamline shaped box girder is put forward. And then, the steel cables of one steel box girder cable-stayed bridge are replaced by FRP cables using the equivalent stiffness method. The bridge tower remains the reinforced concrete structure. Thus, a FRP cable-stayed bridge is completed, which contributes the research platform of the following research.2. Based on the equation of the self-excited force by SCANLAN, and the theory of forced oscillation method for measuring the flutter derivatives, the CFD method is taken to simulate the wind field, so as to obtain the flutter derivatives for the streamline shaped box girder of the three-span bridge. Subsequently, two flutter analysis method, namely the two-dimensional SCANLAN method and the three-dimensional full order flutter analysis method, are taken to calculate the flutter critical wind speed of the FRP cable-stayed bridge, which is compared with the results of the steel box girder bridge.3. Based on the concept of the coefficient of the tri-component static forces and CFD techniques, the coefficients for the static force are calculated by numerical simulations on the platform FLUENT6.3. And then, the aerostatics stability analysis of the bridge can be carried. In every analysis, the FRP bridge and the steel bridge are analyzed respectively, and the .results are compared with each other.4. Based on the WAWS (Weighted Amplitude Wave Superposition) method, the wind field of the bridge is simulated, and the wind speed time series are obtained. Afterwards, the wind speed time series can be transformed to buffet forces time series, so the time domain buffeting analysis of the FRP cable-stayed bridge and steel cable-stayed bridge can be performed respectively.5. From the aspects of self-weight and flutter critical wind speed, the ultimate span of FRP cable-stayed bridge is explored, and the span limit of this bridge under some certain circumstances is advised.In conclusion, compared with the steel cable-stayed bridge, the wind-resistant capability of FRP cable-stayed bridge decreases to some extent. However, in the ultimate span domain, FRP is an ideal material to replace the traditional steel and reinforced concrete materials in long-span cable-stayed bridges. The application of FRP can make best of its advantages, thus it can lighten the self-weight and increase the durability of bridges.