• Geomechanics and Engineering
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• v.6 no.5
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• pp.455-467
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• 2014

As the traffic increased, the original capacity of the tunnel has been unable to meet the needs, so it must be expanded. Based on the features of tunnel, the intermittent trough method must be supposed for tunnel enlarging. Under the situation on the buried deep of the tunnel, it could be used the reasonable arch axis model to descript the past covered rock pressure for mechanism calculating of self-bearing arch. Then establish the three-arch combination effectible model for the analysis which is relied on the tunneling enlarging to Chongqing Yu-Zhou tunnel. It has determined the proper width for the intermittent trough in shallow buried tunnel enlarging.

• Journal of Korean Association for Spatial Structures
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• v.18 no.3
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• pp.83-91
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• 2018

In this study, we investigated the dynamic stability of the system and the semi-analytical solution of the shallow arch. The governing equation for the primary symmetric mode of the arch under external load was derived and expressed simply by using parameters. The semi-analytical solution of the equation was obtained using the Taylor series and the stability of the system for the constant load was analyzed. As a result, we can classify equilibrium points by root of equilibrium equation, and classified stable, asymptotical stable and unstable resigns of equilibrium path. We observed stable points and attractors that appeared differently depending on the shape parameter h, and we can see the points where dynamic buckling occurs. Dynamic buckling of arches with initial condition did not occur in low shape parameter, and sensitive range of critical boundary was observed in low damping constants.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.161-168
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• 2004

The dynamic instability of snapping phenomena has been studied by many researchers. Few papers deal with dynamic buckling under loads with periodic characteristics, and the behavior under periodic excitations is expected to be different from behavior under STEP excitations. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidally shaped arch structures are subjected to sinusoidally distributed excitations with pin-ends. The mechanisms of dynamic indirect snapping of shallow arches are especially investigated under not only STEP function excitations but also under sinusoidal harmonic excitations, applied in the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equation of motion, and examined by Fourier spectral analysis in order to get the frequency-dependent characteristics of the dynamic instability for various load levels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.819-823
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• 2003

The differential equations governing the shape of displacement for the shallow parabolic arch subjected to multiple dynamic point step loads were derived and solved numerically The Runge-Kutta method was used to perform the time integrations. Hinged-hinged end constraint was considered. Based on the Budiansky-Roth criterion, the dynamic critical point step loads were calculated and the dynamic stability regions for such loads were determined by using the data of critical loads obtained in this study.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.5
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• pp.8-13
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• 2004

In order to better understand the characteristics of the flow field around the submerged hydrofoil of finite span with high speed and shallow submergence. a numerical code which can solve the flow around a fast lifting body under the free surface was developed and used to obtain various interesting features of the flow. The code was based on the panel method of Hess( 1972), and the free surface condition was linearized to conform with the assumption of the high Froude number. It is shown that the effect of the change of submerged depth. angle of attack and aspect ratio upon the sectional lift coefficient is rather significant for the case of the chosen example wing, which has the rectangular planform. Since Lee(2002)'s theoretical results were for the wing of elliptical planform, the direct comparison of the two results was not possible. It seems that more computational results are in need to compare the theoretical and the numerical prediction in detail.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.1
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• pp.75-89
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• 2014

In recent years, utilization of underground space has been increasing in various parts of the world. In particular, open-cut method is usually applied to the shallow depth excavation. However some problems such as extreme traffic congestion and unstability of adjacent structures etc. might occur. In order to cope with these problems, the M-CAM (Modified Cellular Arch Method) method was proposed to excavate soil tunnels at shallow depth with secured enough stability and minimized construction period. In this study, sensitivity analysis was performed to predict the influence of the size of CPW(Continuous Pile Wall) and ground conditions on the behavior of the tunnel. First of all, embedded depth and diameter (or thickness) of CPW, coefficient of lateral earth pressure, and ground conditions were selected as parameters that could affect tunnel stability. Meanwhile, FLAC 2D based on finite difference method was used for numerical analysis. As a result of this study, it was checked out that embedded depth among sizes of CPW had a greatest influence on the stability of a tunnel.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.69-76
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• 2003

We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal harmonic excitation with pin-ends. In nonlinear dynamics, examining the characteristics of attractor on the phase plane and investigating the dynamic buckling process are very important thing for understanding why unstable phenomena are sensitively originated by various initial conditions. In this study, the direct and the indirect snap-buckling of shallow arches considering geometrical nonlinearity are investigated numerically and compared with the step excitation critical load.

• Proceeding of KASS Symposium
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• 2008.05a
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• pp.107-112
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• 2008

This paper investigates the variation of post-buckling behaviours of 2-dimensional shallow arch type truss after sizing optimization. The mathematical programming technique is used to produce the optimum member size of 2D arch truss against a central point load. Total weight of structure is considered as the objective function to be minimized and the displacement occurred at loading point and member stresses of truss are used as the constraint functions. The finite difference method is used to calculate the design sensitivity of objective function with respect to design variables. The postbuckling analysis carried out by using the geometrically nonlinear finite element analysis code ISADO-GN. It is found to be that there is a huge change of post-buckling behaviour between the initial structure and optimum structure. Numerical results can be used as useful information for future research of large spatial structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.3
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• pp.1-9
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• 1986

Dynamic stability of parabolic shallow arches, which are supported by hinges at both ends, is investigated. The Runge-Kutta method is used to perform time integrations of the differential equations of motion with proper boundary conditions. Based on Budiansky-Roth criterion, dynamic critical load combinations are evaluated numerically for cases of step loads of infinite duration and impulse loads, individually. The results are plotted to get interaction curves. The loci of the dynamic critical loads, which are obtained in this study, are proposed as boundaries between the dynamic stability and instability regions for the parabolic shallow arches. The results for the parabolic shallow arches are also compared with those for sinusoidal arches of the same arch rises. According to the investigation, the dynamic stability regions for the parabolic arches are larger than those for the sinusoidal arches. However, it is shown that the arch rise is the more governing factor than the shape.

• Nonlinear Functional Analysis and Applications
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• v.27 no.2
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• pp.405-432
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• 2022

Cracks in beams and shallow arches are modeled by massless rotational springs. First, we introduce a specially designed linear operator that "absorbs" the boundary conditions at the cracks. Then the equations of motion are derived from the first principles using the Extended Hamilton's Principle, accounting for non-conservative forces. The variational formulation of the equations is stated in terms of the subdifferentials of the bending and axial potential energies. The equations are given in their abstract (weak), as well as in classical forms.