The Dynamic Response Of Submerged Floating Tunnel Under Random Seismic Excitation

Submerged floating tunnel (SFT), also as known as the Archimedes Bridge, is a new hydraulic structure. It is suspended in water in the joint action of its own weight, buoyancy and anchoring system. Based on Archimedes’principle, it is also known as Archimedes bridge. Submerged floating tunnel shows its unique ability to leap in waters where can’t cross by the traditional bridges and tunnels. Submerged floating tunnel is composed by floating tunnel tube structure, anchoring system, and combination of structure between the pipe sections and connected to the cross-strait revetment structure. Due to the special circumstances of the submerged floating tunnel, the tunnel would be subject to a variety of environmental loads, such as waves, currents, earthquakes, etc.Currently, submerged floating tunnel structural response research work focuses on the structural response of the tube under different load and anchor cable structure response. It gives more research on waves, currents and loads, less on earthquake extreme environmental loads of relatively. Dynamic response of the submerged floating tunnel under the ultimate load of the earthquake and the tube and anchor cable of submerged floating tunnel system are studied in this thesis. The concept of floating tunnel, characteristics and overview of development are introduced. The research progress on the structural dynamic response of the floating tunnel under load of the domestic and foreign scholars in recent years are summarized. Then the purpose and significance of the study are discussed.The main contents are as follows:(1)Considering fluid and structure interaction coupling, Structural dynamics equation of submerged floating tunnel under earthquake is established by simplifying anchor cable for straight model. Inputting earthquake acceleration power spectrum through the virtual excitation method, solving the structural dynamics equation, dynamic response of anchor cable under the action of earthquake is analyzed and the displacement and speed power spectrum of the anchor cable are obtained. By the analysis of displacement and speed power spectral, random earthquake excitation suspended in water tunnel anchor cable under the action of dynamic behavior is achieved. (2)Regarding the system connecting tube body and energy dissipation device as research object, the connection pipe body-energy dissipation device vibration model is established. By the use of pseudo-excitation method for the vibration differential equation, the system dynamic response of tube under the action of earthquake is analyzed and the displacement and speed power spectrum of tube are obtained. By the analysis of displacement and speed power spectral, random earthquake excitation suspended in water tunnel tube under the action of dynamic behavior is achieved.