Development and application of steel-concrete-steel composite structures in immersed tunnels
Song Shenyou1 Nie Jianguo2,3 Xu Guoping4 Fan Jiansheng2,3 Tang Liang4 Guo Yutao2,3
1. Administration of Shenzhen-Zhongshan Passage, Guangzhou 510600, China;
2.Key Lab of Civil Engineering Safety and Durability of the Ministry of Education, Tsinghua University, Beijing 100084, China;
3. Beijing Engineering Research Center of Steel and Concrete Composite Structures, Beijing 100084, China;
4. CCCC Highway Consultants Co., Ltd., Beijing 100088, China
Abstract：Immersed tunnels have been increasingly applied to large-scale submerged tunnel projects in recent years, especially for the large-scale submarine tunnels. To study the development trend of the immersed tunnels and offer guidance for engineering design, the history of the immersed tunnels is reviewed and summarized into three stages, namely, steel shell-reinforced concrete structure, reinforced concrete structure, and steel-concrete-steel composite structure. It is found that the compartment steel-concrete-steel (CSCS) composite structures, which are characterized by longitudinal and transverse diaphragms and stiffening ribs, shall be superior to traditional structural forms, and may become a development trend of large-scale immersed tunnels in the future, which is worth being studied and discussed further. Although many researches have focused on steel-concrete-steel composite structures, the investigations on revealing the mechanisms of the out-of-plane performances of CSCS composite structures are still absent, and moreover, current design methods in the concrete code are relatively conservative. Based on the previous studies, 3 beam bending tests and 3 beam shear tests are conducted. Experimental results disclose that current bending design method may lead to good agreements with the experiments, but the restrictions on the spacing of ribs can be relaxed further considering theconstitution requirements on local buckling of flange. However, current shear design method may often result in lower values than the experimental results, and hence the design is relative conservative. Based on theoretical analysis, a shear design method considering the combination of the anti-shear mechanisms of steel-concrete composite truss and steel web is proposed, which agrees well with the test results with a certain margin.
