Mechanical behaviors and experimental study of submerged floating tunnel subjected to local anchor-cable failure. (1st June 2020) - Xiang, Yiqiang
Highlights: Dynamic responses of SFT subjected to local anchor-cable failure are studied. The optimized "finished state" of the SFT is established. The transient processes after cable breakage are monitored. Dynamic evaluation indexes are used to evaluate the impact effects. Abstract: Submerged floating tunnel (SFT) is a new type of cable-supported structure system for strait crossing. Once the local anchor-cable suddenly fails, it will inevitably cause evident vibration and internal force redistributions of the structure. In order to study the dynamic responses and mechanical behaviors of the SFT subjected to abrupt anchor-cable breakage, a model test is conducted by a set of sensors installed on SFT for cable force, tube displacement and strain measurements. The transient dynamic signals following cable failure are tested and analyzed. Dynamic amplification factor (DAF) and dynamic coefficient (DC) are respectively used to evaluate the impact effect from the cable failure. Meanwhile, finite element simulations are also performed within ABAQUS. The establishments of the finished state of SFT before cable breakage and the dynamic cable failure process are presented both in the model test and FE model. Comparisons between the FE predicted values and the experimental results show a good agreement. On this basis, some influence factors are discussed in different cases of the cable-loss positions and the cable forces of ruptured cable, etc. The results show that the finished state of SFT under dead load (tube redundant buoyancy) after cable-force optimizations is more reasonable than that directly applying dead load without any cable-force adjustments, with more uniform cable force distribution and smaller tube deformation. Although the SFT suffers strong oscillations after sudden cable-breakage incident, no progressive collapse occurs when the safety margin of the rest structure is sufficient. The dynamic effect on remaining cable members due to sudden cable failure can be evaluated by DC method. A DC value of 1.5 is recommended to ensure the safety of SFT anchor-cables. When cable failure happens at the mid span of the tunnel, the deformation of SFT tube is most critical.