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As the first waterproof component of the immersed tunnel, it is very important to ensure the remaining compression of the GINA gasket to resist external water intrusion. This paper proposed a method for determining warning thresholds for the remaining compression of the GINA gasket based on a material-to-mechanical analysis. In terms of material analysis, two factors that affect the GINA gasket are investigated: rubber hardness and cross-sectional shape, and they are adopted as the basis for subsequent mechanical analysis. In terms of mechanical analysis, uneven settlement during the operation period is considered to be the major cause of joint deformation, which is further divided into four modes: bending, shear, expansion, and torsion, with the computation model of the GINA gasket established to obtain the warning threshold. After that, a graded early warning method is adopted, and corresponding thresholds are given after an investigation of previous studies, which are validated by a three-dimensional finite element analysis. The deformation monitoring data between the E28 and E29 elements of the Hong Kong–Zhuhai–Macao Bridge Immersed Tunnel are used to verify the proposed method. The results show that the GINA gasket of the Hong Kong–Zhuhai–Macao Bridge Immersed Tunnel is currently in a safe state, and its deformation is much lower than the minimum warning level. [ABSTRACT FROM AUTHOR]

The segmental joints are the weak parts of the immersed tunnel structure, and their deformation characteristics are closely correlated with the waterproof behavior and structural safety of the whole tunnel. In order to study the deformation characteristics of the segmental joints of immersed structure, in this paper, the E13 pipe section in the natural foundation section of an immersed tunnel in the Hong Kong-Zhuhai-Macao Bridge is taken as the research object, and the model test of the immersed tunnel is carried out. The similarity ratio of the model to the prototype is determined according to the actual engineering scale and the capability of the model test system, and the plexiglass is selected as the model material of the immersed tunnel according to the similarity of elastic modulus and density. In the test, various working conditions, including back-silting load and different prestress control values, are analyzed, and the influence of settlement and opening of the immersed tunnel is obtained, along with the stress-strain characteristics of the segment joints. Results show that the increase of the back-silting load will increase the element settlement and the expansion of the segment joints, but the application of prestress increases the overall stiffness of the element, which can effectively restrain the settlement of element and the expansion of joints. Furthermore, based on the model test conditions, a finite element model is established to simulate the mechanical behavior of the immersed tunnel. The settlement curve and stress-strain curve of the numerical analysis are found to be similar to those obtained from the model test, which verifies the reliability of the model test. [ABSTRACT FROM AUTHOR]

Modular building is an innovative construction method and imposes unique assembly requirements. Modular structures may exhibit different global responses and unexpected resisting mechanisms under loading scenarios. However, there is limited research dealing with collapse behavior of steel-framed modular structures exposed to fire. This paper studies numerically the fire-induced collapse behavior of the modular framed steel structures. A six-story modular structure is designed. Finite element analysis is conducted to investigate global deformation, load transfer pattern, structural resisting mechanisms and collapse process of the structures exposed to fire. A series of parametric analysis is conducted to study influences of load ratio, cross-sectional dimensions of columns and fire locations. Results show that the modular structure designed based on Hong Kong building code survives against single module fire, but collapses during traveling fire. The overturning action, bracing effect and double-beam system are developed under fire scenarios. A geometrically unstable system is developed against traveling fire. Moreover, damage spreads from the columns close to the fire compartment to those far away. The robustness of modular structures is greatly influenced by its load ratios and cross-sectional dimensions of the columns. The findings can be adopted as valuable tools for recognizing the vulnerable structural components and critical loading mechanisms of modular structure exposed to fire. A practical design method is proposed to evaluate the final collapse state of the modular structures exposed to fire with good accuracy and efficiency and this provides a practical solution for the structural engineers to process the collapse state of modular structures. • Study fire-induced collapse behaviors of steel-framed modular structures. • Recognize vulnerable frame members of modular structures against fire. • Identify critical loading mechanisms of modular structures against fire. • Investigate influences of load ratios, column sections and fire locations. • Develop a design method to assess collapse state of modular structures against fire. [ABSTRACT FROM AUTHOR]

Numerical modelling, particularly fully-coupled hydro-mechanical large-deformation models, greatly helps in properly simulating the complex failure and post-failure mechanisms of rainfall-induced landslides. The affected soils, in fact, evolve from none or small deformation rates to large deformation rates during the initiation stage and vice-versa during deposition, with relevant interactions between the solid skeleton and interstitial water. The Material Point Method (MPM) has the potential to reproduce entirely those complex processes. However, a comparison with standard tools (e.g. FEM : Finite Element Method, LEM : Limit Equilibrium Method) may guide in the optimal choice (or in the combined use) of the various modelling approaches. A framework is here proposed based on a multi-tool approach consisting in the combination of: a) no-deformation LEM , b) small-deformation FEM , c) large-deformation MPM. The LEM slope stability analyses are performed for a realistic assessment of the major slip surface(s) and to back-analyse uncertain slope parameters. The FEM stress-strain analyses assess the progressive failure, the onset of initial velocity and the later acceleration of the landslide body, until large deformations occur in the slope and numerical convergence of FEM is lost. The MPM analyses are used to reproduce the whole landslide process, from the initiation to propagation and final deposition. Such an integrated framework is tested for an international landslide benchmark (the 1995 Fei Tsui Road landslide in Hong Kong). The results achieved through the different approaches are discussed in relation to the wide scientific literature available for the general topics and the specific case study. The paper highlights that the fully-coupled hydro-mechanical large-deformation model properly reproduces the complex failure and post-failure mechanisms of rainfall-induced landslides. However, no-deformation LEM analyses and small-deformation FEM analyses allow a reasonable understanding of both the pre-failure stage and the failure mechanism. These more traditional tools are confirmed as indispensable tools in the engineering practice and research. • Analysis of an unsaturated slope failure and post-failure stages. • Combining and comparing different approaches. • Modelling of progressive failure. • MPM compared to standard tools. [ABSTRACT FROM AUTHOR]