• Journal of the Korean Society of Hazard Mitigation
• /
• v.6 no.4 s.23
• /
• pp.57-65
• /
• 2006

In this study, hydraulic model same as natural channel with junction area and curved reach is constructed, and after that the variation of difference of the water surface elevation at cross section in junction area is analyzed using constructed hydraulic model. In junction area, the variation of maximum water level based on downstream section is more affected in discharge ratio at upstream than downstream. The maximum water level increased as closed to junction and the peak level appeared at just downstream of junction. The slope of water elevation at cross section is affected in section shape and decreased as discharge ratio is reduce. The expressed formulas developed in the channel consist of constant curvature and section shape showed difference of 60% with measured value, but the suggested formula in this study to compute difference of water surface elevation showed difference of 10% with measured value.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.485-490
• /
• 2000

The effect of curvature, rotation, variable cross-section can make very complex flow pattern in turbo-machinery such as Pumps, compressors, turbines, In this study of turbulent flow characteristics rotating $90^{\circ}$ curved duct under a Plane rate of strain condition is computationally analyzed. The objective of this study is to understand the complex turbulent flow phenomena in turbo-machinery passage by analyzing the modeled rotating $90^{\circ}$ curved duct flow. RSM(Reynolds Stress Model) was employed for the turbulence modeling of Reynolds stress in momentum equations proposed by Shin(1995). The three dimensional computational code which adopts RSM for trubulence modeling was newly developed for the generalized curvilinear coordinate.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.906-915
• /
• 2004

Derivation procedures of exact dynamic stiffness matrices of thin-walled curved beams subjected to axial forces are rigorously presented for the spatial free vibration analysis. An exact dynamic stiffness matrix is established from governing equations for a uniform curved beam element with nonsymmetric thin-walled cross section. Firstly this numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. Thus, displacement functions of dispalcement parameters are exactly derived and finally exact stiffness matrices are determined using clement force-displacement relationships. The natural frequencies of the nonsymmetric thin-walled curved beam are evaluated and compared with analytical solutions or results by ABAQUS's shell elements in order to demonstrate the validity of this study.

• Structural Engineering and Mechanics
• /
• v.33 no.3
• /
• pp.307-323
• /
• 2009

This article presents the differential system that governs the mechanical behaviour of a curved-beam element, with varying cross-section area, subjected to generalized load. This system is solved by an exact procedure or by the application of a new numerical recurrence scheme relating the internal forces and displacements at the two end-points of an increase in its centroid-line. This solution has a transfer matrix structure. Both the stiffness matrix and the equivalent load vector are obtained arranging the transfer matrix. New structural matrices have been defined, which permit to determine directly the unknown values of internal forces and displacements at the two supported ends of the curved-beam element. Examples are included for verification.

• Structural Engineering and Mechanics
• /
• v.33 no.4
• /
• pp.447-484
• /
• 2009

The spatially coupled buckling, in-plane, and lateral bucking analyses of thin-walled Timoshenko curved beam with non-symmetric, double-, and mono-symmetric cross-sections resting on elastic foundation are performed based on series solutions. The stiffness matrices are derived rigorously using the homogeneous form of the simultaneous ordinary differential equations. The present beam formulation includes the mechanical characteristics such as the non-symmetric cross-section, the thickness-curvature effect, the shear effects due to bending and restrained warping, the second-order terms of semitangential rotation, the Wagner effect, and the foundation effects. The equilibrium equations and force-deformation relationships are derived from the energy principle and expressions for displacement parameters are derived based on power series expansions of displacement components. Finally the element stiffness matrix is determined using force-deformation relationships. In order to verify the accuracy and validity of this study, the numerical solutions by the proposed method are presented and compared with the finite element solutions using the classical isoparametric curved beam elements and other researchers' analytical solutions.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.341-344
• /
• 2006

A study for the nonlinear analysis of segmentally erected curved PSC(prestressed concrete) cable-stayed bridge considering the effects due to large deflections is presented. Various case studies regarding the effects of the material nonlinearities and the geometric nonlinearities on the behavior of segmentally erected curved PSC cable-stayed bridge are conducted. The numerical results on the bridge which has relatively low stress profile through the bridge deck section like the example herein show that the geometric nonlinearities has more significant effects on the structural behavior than the material nonlinearities.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1281-1288
• /
• 1994

Beams curved in plan are often designed with the circular curved member system including warping effects. In this study, the curved bridges are idealized as the circular curved member system with singly symmetric cross sections and simply supported ends. Displacement fields of them to satisfy the boundary conditions are expanded by Fourier series and the governing equation of natural frequencies of them is derived. The distributions of the characteristics of natural frequencies of them are shown according to the variations of relevant parameters-angle of intersection, curvature, and parameter of symmetry of cross section which can represent the properties of the curved bridges. A parametric study is conducted to investigate the effect of relevant parameters on natural frequencies.

• 한국가시화정보학회:학술대회논문집
• /
• 2007.11a
• /
• pp.116-118
• /
• 2007

Three-dimensional (3D) velocity field information of a laminar flow in a curved micro tube of circular cross-section has been measured using a digital micro holographic particle tracking velocimetry (HPTV). The temporal evolution of instantaneous velocity field of a water flow in a curved micro tube of $100\;{\mu}\;m$ and $300\;{\mu}\;m$ in inner diameter was obtained. The 3D mean velocity field distribution was obtained quantitatively by statistical-averaging of instantaneous velocity fields. At low Dean number (De), a secondary flow was not generated in the curved tube. With increasing Dean number, the secondary flow constituted of two large-scale counter-rotating vortices was formed due to enhanced centrifugal force. To reveal the flow characteristics of high Dean numbers, trajectories of fluid particles were evaluated experimentally from the 3D velocity fields data measured by the HPTV technique. The present experimental results, especially the 3D particle trajectories, would be helpful to design and to understand the mixing phenomena in 3D curved passages of various curved micro-tubes or micro-channels.

• Structural Engineering and Mechanics
• /
• v.88 no.1
• /
• pp.83-94
• /
• 2023

An accurate and highly efficient inverse element labelled iPCB is developed based on the inverse finite element method (iFEM) for real-time shape estimation of plane-curved structures (such as arch bridges) utilizing onboard strain data. This inverse problem, named shape sensing, is vital for the design of smart structures and structural health monitoring (SHM) procedures. The iPCB formulation is defined based on a least-squares variational principle that employs curved Timoshenko beam theory as its baseline. The accurate strain-displacement relationship considering tension-bending coupling is used to establish theoretical and measured section strains. The displacement fields of the isoparametric element iPCB are interpolated utilizing nonuniform rational B-spline (NURBS) basis functions, enabling exact geometric modelling even with a very coarse mesh density. The present formulation is completely free from membrane and shear locking. Numerical validation examples for different curved structures subjected to different loading conditions have been performed and have demonstrated the excellent prediction capability of iPCBs. The present formulation has also been shown to be practical and robust since relatively accurate predictions can be obtained even omitting the shear deformation contributions and considering polluted strain measures. The current element offers a promising tool for real-time shape estimation of plane-curved structures.

• Proceedings of the KSME Conference
• /
• 2000.11b
• /
• pp.467-472
• /
• 2000

Most of the past experimental or analytical studies were performed for the curved bend with a square cross-section. Velocity profiles and Reynolds stresses of the turbulence flow in the 270 degree bend with circular cross-section were measured by a hot-wire anemometer. The mean velocity of primary flowing direction effected by the downstream of bend in the entry region of the bend. The flow in the inner part of the bend slowed the distribution velocity relatively large and unsymmetric phenomenon. In the strong secondary flow occurred when the flow passed in the region of 45 degree to 90 degree. The secondary flow appeared very large value in the neighbor region of inner wall.