• Journal of the Korea Concrete Institute
• /
• v.17 no.4 s.88
• /
• pp.535-542
• /
• 2005

Two series of experiments on the performance of beam-column joints in High-Strength Reinforced concrete frames were carried out. Main experimental parameters were : concrete strength, column axial load and amount of joint hoop reinforcement. Test result showed that the ultimate shear strength of exterior joints increased of column axial compressive force and the amount of the joint hoop reinforcements. Through the regression analysis on the 24data, the following equation is obtained $jv_u=(2.935{\times}10-3\;{\rho}jw{\cdot}fy\;+\;0.365){\sqrt{f_{ck}}}$

• Journal of the Korea Concrete Institute
• /
• v.11 no.3
• /
• pp.81-88
• /
• 1999

In order to properly evaluate the shear strength of reinforced concrete circular columns due to the transverse shear reinforcement, the average of fractions of forces generated along the circular transverse hoops across the shear failure plane in the loading direction is calculated. For this, the center-to-center diameter of circular transverse hoops. spacing and the crack angle measured to the column longitudinal axis are considered. Using these variables, an equation representing the effective section area of circular transverse shear steel is proposed. The study result shows that the constant parameter. used for the calculation of the effective section area of circular hoops over the last 10 years, should not universally be applied any more. The use of the constant parameter may not seriously do harm to the evaluation of shear strength for circular columns with non-seismically designed transverse hoop reinforcement, since it gives slightly conservative results. However. for well-confined circular columns with close spacing or circular steel jacketing. it gives about 20% overestimation of the shear capacity contributed by the transverse hoop steel.

• Journal of Aerospace System Engineering
• /
• v.12 no.1
• /
• pp.47-56
• /
• 2018

In this paper, the structural analysis of the Geostationary Korea Multi-Purpose Satellite-2 (GEO-KOMPSAT-2) tubing system is discussed, and the structural integrity of the tubing system is assessed by comparative analysis with the results of overseas partner AIRBUS. Securing structural reliability of the tubing system is a very important key element of the propulsion system of the GEO-KOMPSAT-2 satellite. Therefore, FE modeling of the propulsion tubing was carried out directly using the CAE program, and structural analysis was performed to evaluate the stress state under launch conditions. Hoop stress, axial stress, bending stress, and torsion stress were calculated according to diverse load conditions by using pressure stress analysis, thruster alignment analysis, sine qualification load analysis, and random qualification load analysis. From the results, the Margin of Safety (MoS) of the tubing system is evaluated, and we can verify the structural integrity of the tubing system when subjected to various launch loads.

• Computers and Concrete
• /
• v.29 no.4
• /
• pp.219-235
• /
• 2022

Strengthening slender reinforced concrete (RC) columns is a challenge. They are susceptible to overall buckling that induces bending moment and axial compression. This study presents the precise three-dimensional finite element modeling of slender RC columns strengthened with fiber-reinforced polymer (FRP) composites sheets with various patterns under concentric or eccentric compression. The slenderness ratio λ (height/width ratio) of the studied columns ranged from 15 to 35. First, to determine the optimal modeling procedure, nine alternative nonlinear finite element models were presented to simulate the experimental behavior of seven FRP-strengthened slender RC columns under eccentric compression. The models simulated concrete behavior under compression and tension, FRP laminate sheets with different fiber orientations, crack propagation, FRP-concrete interface, and eccentric compression. Then, the validated modeling procedure was applied to simulate 58 FRP-strengthened slender RC columns under compression with minor eccentricity to represent the inevitable geometric imperfections. The simulated columns showed two cross sections (square and rectangular), variable λ values (15, 22, and 35), and four strengthening patterns for FRP sheet layers (hoop H, longitudinal L, partial longitudinal L_w, and longitudinal coupled with hoop LH). For λ=15-22, pattern L showed the highest strengthening effectiveness, pattern L_w showed brittle failure, steel reinforcement bars exhibited compressive yielding, ties exhibited tensile yielding, and concrete failed under compression. For λ>22, pattern L_w outperformed pattern L in terms of the strengthening effectiveness relative to equivalent weight of FRP layers, steel reinforcement bars exhibited crossover tensile strain, and concrete failed under tension. Patterns H and LH (compared with pattern L) showed minor strengthening effectiveness.

• Geomechanics and Engineering
• /
• v.31 no.3
• /
• pp.237-248
• /
• 2022

Nowadays, more and more subway tunnels were planed and constructed underneath the ground of urban cities to relieve the congested traffic. Potential damage may occur in existing tunnel if the new tunnel is constructed too close. So far, previous studies mainly focused on the tunnel-tunnel interactions with circular shape. The difference between circular and horseshoe shaped tunnel in terms of deformation mechanism is not fully investigated. In this study, three-dimensional numerical parametric studies were carried out to explore the effect of different tunnel shapes on the complicated tunnel-tunnel interaction problem. Parameters considered include volume loss, tunnel stiffness and relative density. It is found that the value of volume loss play the most important role in the multi-tunnel interactions. For a typical condition in this study, the maximum invert settlement and gradient along longitudinal direction of horseshoe shaped tunnel was 50% and 96% larger than those in circular case, respectively. This is because of the larger vertical soil displacement underneath existing tunnel. Due to the discontinuous hoop axial stress in horseshoe shaped tunnel, significant shear stress was mobilized around the axillary angles. This resulted in substantial bending moment at the bottom plate and side walls of horseshoe shaped tunnel. Consequently, vertical elongation and horizontal compression in circular existing tunnel were 45% and 33% smaller than those in horseshoe case (at monitored section X/D = 0), which in latter case was mainly attributed to the bending induced deflection. The radial deformation stiffness of circular tunnel is more sensitive to the Young's modulus compared with horseshoe shaped tunnel. This is because of that circular tunnel resisted the radial deformation mainly by its hoop axial stress while horseshoe shaped tunnel do so mainly by its flexural rigidity. In addition, the reduction of soil stiffness beneath the circular tunnel was larger than that in horseshoe shaped tunnel at each level of relative density, indicating that large portion of tunneling effect were undertaken by the ground itself in circular tunnel case.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.2E
• /
• pp.53-58
• /
• 1998

In this paper, we study the response of several anisotropic systems to buried transient line loads. The problem is mathematically formulated based on the equations of motion in the constitutive relations. The load is in form of a normal stress acting with arbitrary axis on the plane of monoclinic symmetry. Plane wave equation is coupled with vertical shear wave, longitudinal wave and horizontal shear wave. We first considered the equation of motion in reference coordinate system, where the line load is coincident with symmetry axis of the orthotrioic material. Then the equation of motion is transformed with respect to general coordiante system with azimuthal angle by using transformation tensor. The load is first described as a body force in the equations of the motion for the infinite media and then it is mathematically characterized. Subsequently the results for semi-infinite spaces is also obtained by using superposition of the infinite medium solution together with a scattered solution from the free surface. Consequently explicit solutions for the displacements are obtained by using Cargniard-DeHoop contour. Numerical results which are drawn from concrete examples of orthotropic material belonging to monoclinic symmetry are demonstrated.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.3E
• /
• pp.35-42
• /
• 1998

Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. It is known that the fourier method has advantages in memory requirements and computing speed over conventional methods such as FDM and FEM, because the Fourier method needs less grid points for achieving the same accuracy. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

• Transactions of Materials Processing
• /
• v.12 no.2
• /
• pp.116-122
• /
• 2003

In the Prestressed die design for cold working, many constraining conditions should be considered to insure the die safety and to improve the dimension accountancy products. Among the constraining conditions, yielding conditions, diameter ratios and interferences between rings are very important. . In this paper, therefore, flexible tolerance method was used in order to search the optimum values of design variables. The maximum inner pressure is used as objective function in this numerical analysis. In the design Process, it was also involved the safety factor to the yield strength of each ring by considering the allowable tensile or compressive hoop stress in each ring. The proposed technique has been applied to the die design of backward extrusion process, and it's analytical results have been compared with that of the conventional design method.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.3
• /
• pp.707-715
• /
• 1994

This study presents thickness optimization for the pressure vessel domes subject to internal pressure and axial force simultaneously. The considered typical pressure vessel domes are ellipsoidal and tori-spherical domes with skirt and nozzle part. These pressure vessel domes under loading have higher stress concentration on geometric discontinuity parts. Therefore, thickness optimization of axi-symmetric pressure vessel domes is essentially concerned on minimizing this stress concentration. The objective function is minimization of weight of pressure vessel dome. The design variable is thickness of dome and cylinder. Considered constraint is Von Mises equivalent stress. In the optimization procedure, ANSYS code is used. The equivalent and hoop stress of original shape domes are compared with those of optimal shape domes. And optimal thicknesses for pressure vessel domes are presented.

• Proceedings of the KIEE Conference
• /
• 2006.04b
• /
• pp.77-79
• /
• 2006

변압기에서 단락기계력에 대한 계산 분야는 수직력에 의한 Beam Bending, Tillting, 절연물 압축력과 수평력에 의한 Hoop, Compression 등이 있다. 본 논문은 전력용변압기 내부의 자계를 자기영상법을 이용하여 구하고 계산된 자계를 이용하여 단락 기계력을 구하는 방법을 제안하고자 한다. 또한 기존 FEM과 자기영상법과의 계산결과를 비교하였다.