• Geomechanics and Engineering
• /
• v.33 no.5
• /
• pp.439-451
• /
• 2023

The construction of shield tunnelling in urban sites is facing serious risks from complex and changeable underground conditions. Construction problems in the sand-clay mixed ground have been more reported in recent decades for its poor control of soil loss in tunnel face, ground settlement and supporting pressure. Since the limitations of observation methods, the conventional physical modelling experiments normally simplify the tunnelling to a plane strain situation whose results are not reliable in mixed ground cases which exhibit more complicated responses. We propose a new method for the study of the mixed ground tunnel through which mixed lays are simulated with transparent soil surrogates exhibiting different mechanical properties. An experimental framework for the transparent soil modelling of the mixed ground tunnel was established incorporated with the self-developed digital image correlation system (PhotoInfor). To understand better the response of face stability, ground deformation, settlement and supporting phenomenon to tunnelling excavation in the sand-clay mixed ground, a series of case studies were carried out comparing the results from cases subjected to different buried depths and mixed phenomenon. The results indicate that the deformation mode, settlement and supporting phenomenon vary with the mixed phenomenon and buried depth. Moreover, a stratigraphic effect exists that the ground movement around mixed face reveals a notable difference.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.5
• /
• pp.435-441
• /
• 1984

The matrix method, as an effective FEM formulation for the analysis of rigid-plastic deformation, was applied to the bore expanding of anisotropic sheet metal. The effect of planar anisotropy on sheet metal deformation was studied for bore expanding process under the uniform radial stretching condition, and the results were compared with isotropic and normal anisotropic solutions. Experiments were carried out using a flat punch for cold-rolled sheet metal. The experimental results were compared with computations from the matrix method with the boundary conditions corresponding to actual experiment. Both in theory and experiment, it is found that the maximum thinning which results in necking occurs in the direction of the minimum R-value. The results also suggest that the matrix method is efficient for analyzing planar anisotropic sheet metal. The comparison between theory and experiment suggests that Hill's theory of planar anisotropy is somewhat exaggerated. However, the theoretical predictions are in qualitative agreement with the experimental results.

• Structural Engineering and Mechanics
• /
• v.68 no.5
• /
• pp.603-619
• /
• 2018

In this research, an effective computational technique is carried out for nonlinear and post-buckling analyses of cracked imperfect composite plates. The laminated plates are assumed to be moderately thick so that the analysis can be carried out based on the first-order shear deformation theory. Geometric non-linearity is introduced in the way of von-Karman assumptions for the strain-displacement equations. The Ritz technique is applied using Legendre polynomials for the primary variable approximations. The crack is modeled by partitioning the entire domain of the plates into several sub-plates and therefore the plate decomposition technique is implemented in this research. The penalty technique is used for imposing the interface continuity between the sub-plates. Different out-of-plane essential boundary conditions such as clamp, simply support or free conditions will be assumed in this research by defining the relevant displacement functions. For in-plane boundary conditions, lateral expansions of the unloaded edges are completely free while the loaded edges are assumed to move straight but restricted to move laterally. With the formulation presented here, the plates can be subjected to biaxial compressive loads, therefore a sensitivity analysis is performed with respect to the applied load direction, along the parallel or perpendicular to the crack axis. The integrals of potential energy are numerically computed using Gauss-Lobatto quadrature formulas to get adequate accuracy. Then, the obtained non-linear system of equations is solved by the Newton-Raphson method. Finally, the results are presented to show the influence of crack length, various locations of crack, load direction, boundary conditions and different values of initial imperfection on nonlinear and post-buckling behavior of laminates.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2003.03a
• /
• pp.365-368
• /
• 2003

Despite of the simple equipment and operation, DMT has been widely used to obtain various soil parameters and those parameters have been successfully applied to geotechnical design practice. Among them, the estimation of horizontal coefficient of consolidation is so useful that many researchs recently have been carried out. However, simulation of the penetration of the DMT blade is complex due to the inherent difficulty on analyzing a plane strain deformation of the soil around blade. Therefore, empirical and semi-empirical methods that use the theoretical solution developed fur piezocone with some assumptions have been used to estimate the coefficient of consolidation from Dilatometer dissipation test. In this paper, coefficients of consolidation c$\_$h/ which were obtained using equivalent radius that is same area with the DMT blade and optimization technique are compared with those obtained from Oedometer test and other interpretation methods. It was found that a new method used in this study can give more precise horizontal coefficient of consolidation than other methods do.

• Structural Engineering and Mechanics
• /
• v.57 no.2
• /
• pp.281-294
• /
• 2016

The paper is devoted to study a mesh-free analysis method of structural elements of engineering structures based on B-spline Wavelet Basis Function. First, by employing the moving-least square method and the weighted residual method to solve the structural displacement field, the control equations and the stiffness equations are obtained. And then constructs the displacement field of the structure by using the m-order B-spline wavelet basis function as a weight function. In the end, the paper selects the plane beam structure and the structure with opening hole to carry out numerical analysis of deformation and stress. The Finite Element Method calculation results are compared with the results of the method proposed, and the calculation results of the relative error norm is compared with Gauss weight function as weight function. Therefore, the clarification verified the validity and accuracy of the proposed method.

• Architectural research
• /
• v.18 no.3
• /
• pp.113-120
• /
• 2016

The stability and resistance of the plates under in-plane loading is crucial in the design of structures. For the assessment of structural stability, it is necessarily required to have accurate finite element technologies. Therefore, the enhanced 9-node plate (Q9-ANS) element is introduced for the linear buckling analysis of plate where the critical buckling load has to be determined. The Q9-ANS is developed with the Reissner-Mindlin (RM) assumptions which consider transverse shear deformation of the plate. Assumed shear strain is used to alleviate the shear locking phenomenon. Numerical examples are carried out to verify the performance of the Q9-ANS element in calculation of critical buckling load of the plates.

• Steel and Composite Structures
• /
• v.24 no.6
• /
• pp.741-751
• /
• 2017

A steel slit shear wall has vertical slits and when it is under lateral loads, the section between these slits has double-curvature deformation, and by forming a flexural plastic hinge at the end of the slit, it dissipates the energy on the structure. In this article, Experimental, numerical and analytical analyses are performed to study the effect of slit shape and edge stiffener on the behavior of steel slit shear wall. Seismic behavior of three models with different slit shapes and two models with different edge stiffener shapes are studied and compared. Hysteresis curves, energy dissipation, out of plane buckling, initial stiffness and strength are discussed and studied. The proposed slit shape reduces the initial stiffness, increases the strength and energy dissipation. Also, edge stiffener shape increases the initial stiffness significantly.

• Transactions of Materials Processing
• /
• v.11 no.4
• /
• pp.332-340
• /
• 2002

The light guide plate of the TFT-LCD reflects the light originated from the light source, and guides the light to the front side of LCD so that we can see images vividly. This paper is concerned with tile injection molding of the light guide plate for the reflective typed LCD related to IMT-2000. The finite element analysis has been carried out based on the pine stress theory to predict both the thermal stresses of the products in the post-filling stage and the in-plane deformation behavior of the products after ejection process. Based on the simulation results, the mold for the light guide plate of a 2inch sized LCD has been designed.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.11a
• /
• pp.107-110
• /
• 2005

In this study we investigated the shear and forming behavior of chain stitched multi-axial warp knitted fabric preform, so called non-crimp fabric (NCF). The picture frame test was performed to characterize the shear behavior of NCF and also provide material properties for the numerical simulation of its deformation behavior. The forming behavior of NCF with chain stitch were investigated using hemispherical forming tools. The experimental results show that processing conditions such as blank holder force (BHF) and preform shape are crucial to determining the forming behavior of NCF. For instance, an asymmetric formed shape, which is due to the stitches introduced to NCF, turns into a symmetric one as BHF increases. Furthermore the in-plane and out-of buckling (wrinkle), the severance of which were quantified using image processing method, decreases significantly as BHF increases.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.459-459
• /
• 2011

Graphene has many fascinating material properties such as high electron mobility, high optical transparency, excellent thermal conductivity, superior Young's modulus, etc. Several studies have recently found that single-layer graphene is chemically more reactive than few-layer graphene when supported on silicon dioxide substrates with sub-nm roughness. In this study, we have investigated the influence of substrates on chemical reactivity of graphene. Morphology and thermal oxidation behavior of graphene on atomically flat mica substrates were studied by atomic force microscopy (AFM) and Raman spectroscopy compared to graphene on SiO2/Si substrates. Notably, oxidation of single-layer graphene proceeds more slowly on mica than SiO2/Si. Detailed analysis led to a conclusion that deformation along the out-of-plane direction enhances reactivity of graphene.