THE NEW TREND OF COMPARTMENT STEEL-CONCRETE-STEEL COMPOSITE STRUCTURES IN IMMERSED TUNNELS
Yu-Tao Guo 1,2, Jian-Sheng Fan 1,2* and Jian-Guo Nie 1,2
1 China Key Lab. of Civil Engineering Safety and Durability of China Education Ministry, Dept. of Civil Engineering, Tsinghua University, Beijing, China
2 Beijing Engineering Research Center of Steel and Concrete Composite Structures, Beijing, China
The compartment steel-concrete-steel (CSCS) sandwich composite structures which are characterized with orthogonal longitudinal and transverse steel diaphragms (webs) exhibit superiorities in capacity and construction efficiency compared to traditional engineering structures, offering a competitive choice for the application of mega immersed tunnels. The history and development of immersed tunnels have been reviewed and it is found that there had been three historical stages: steel shell structures; reinforced concrete (RC) structures and steel-concrete-steel composite structures. The utilizations of SCS composite structures in immersed tunnels are summarized and different types of SCS structures are presented. To reveal the mechanisms of the out-of-plane performances of CSCS composite structures, bending and shear tests are designed and conducted by the authors. It is found that the current design method cannot predict the shear capacity satisfactorily and some of the structural restrictions could be loosen. Based on the literature review and the tests, several suggestions have been proposed for the design of CSCS composite structure immersed tunnels.
Steel-concrete-steel composite structure; Metal and composite structure; Immersed tunnel; Mega structure; Bending capacity; Shear capacity