• Steel and Composite Structures
• /
• v.39 no.5
• /
• pp.565-581
• /
• 2021

In this paper the buckling analysis of the nanoplate made of arbitrary bi-directional functionally graded (BDFG) materials with small scale effects are investigated. To study the small-scale effects on buckling load, the Eringen's nonlocal theory is applied. Employing the principle of minimum potential energy, the governing equations are obtained. Generalize differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the buckling load of BDFG nanoplates. These models can degenerate into the classical models if the material length scale parameter is taken to be zero. Comparison between the results of GDQ method and other papers for buckling analysis of a simply supported rectangular nano FGM plate reveals the accuracy of GDQ method. At the end some numerical results are presented to study the effects of material length scale parameter, plate thickness, aspect ratio, Poisson's ratio boundary condition and side to thickness ratio on size dependent Frequency.

• Steel and Composite Structures
• /
• v.38 no.3
• /
• pp.305-317
• /
• 2021

The mechanical behavior of the outer square inner circular concrete-filled dual steel tubular (SCCFT) stub columns under axial compression is investigated by means of experimental research, numerical analysis and theoretical investigation. Parameters such as diameter ratio, concrete strength and steel ratio were discussed to identify their influence on the mechanical properties of SCCFT short columns on the basis of the experimental investigation of seven SCCFT short columns. By establishing a finite element model, nonlinear analysis was performed to discuss the longitudinal and transverse stress of the dual steel tubes. The longitudinal stress characteristics of the core and sandwich concrete were also analyzed. Furthermore, the failure sequence was illustrated and the reasonable cross-section composition of SCCFT stub column was proposed. A formula to predict the axial load capacity of SCCFT stub column was advanced and verified by the results from experiment and the finite element.

• Journal of Institute of Convergence Technology
• /
• v.12 no.1
• /
• pp.7-12
• /
• 2022

The reduction ratio of the magnetic gear is determined by the ratio of the number of poles between the high-speed permanent magnet layer and the low-speed permanent magnet layer. In general, it is known that the greater the least common multiple of both poles, the smaller the torque ripple called by cogging of the magnetic force generated in the magnetic gear. However, little is known about the effect of the harmonic modulator that filters the magnetic field in the magnetic gear to magnetically couple the high-speed side and the low-speed side except for the number of poles. In this study, torque ripple characteristics according to changes in modulator shape such as opening ratio and tooth thickness are analyzed using a finite element analysis tool.

• Journal of Korean Society of Forest Science
• /
• v.99 no.6
• /
• pp.808-815
• /
• 2010

This study is to give informations about management Situations and investment returns to someone who will newly cultivate schizandra or expand area of culture. This study used IRR, B/C Ratio and NPV for beneficial analysis. We surveyed fifty one among schizandra cultivation farmhouses in chief producing districts Gangwon Inje, Gyeongbuk Munkyung, Kyungnam Sancheong and Jeonnam Whasoon in Korea from May till September in 2009. So this study surveyed about inputted labors and materials, land price and etc. by working process to calculate producing and operating cost. Fruits of schizandra are sold from 5,000 won to 6,000 won per kg at locals. And IRR(Internal Rate of Returns), B/C Ratio and incomes ratio is calculated by three senarios 5,000 won, 5,500 won and 6,000 won per kg at locals. Discount rate is 3.00%. As the result of this study IRRs are -16.00%, -6.91%, 0.40% one after another and B/C Ratios are 0.81, 0.89, 0.97 one after another. And schizandra cultivation isn't profitable. When price of schizandra fruits is 6,200 won per kg, IRR is 3.00% and B/C Ratio is 1.00. Therefore, if price of schizandra fruits is over 6,200 won per kg, we judge that it is profitable. And income ratio is 23.9% on 6,200 won per kg.

• Journal of Korean Association for Spatial Structures
• /
• v.16 no.3
• /
• pp.47-58
• /
• 2016

Cable network system is a flexible lightweight structure which curved cables can transmit only tensile forces. The weight of cable roof dramatically can reduce when the length becomes large. The cable network system is too flexible, most cable systems are stabilized by pretension forces. The tensile force of cable system is greatly influenced by the sag ratio and pretension forces. Determining initial sag ratio of cable roof system is essential in a design process of cable structures. Final sag ratio and pretension depends on initial installed sag and on proper handling during installation. The design shape of cable system has an affect on the sag and pretension, and must be determined using well-defined design philosophy. This paper is carried out the comparative data of the deflection and tensile forces on the geometric non-linear analysis of cable network systems according to sag ratio. The study of cable network system is provided to technical informations for the design of a large span cable roof, analytical results are compared with the results of other researchers. Structural nonlinear analysis of systems having cable elements is relatively complex than other rigid structural systems because displacements are large as a reason of flexibility, initial prestress is applied to cables in order to increase the rigidity, and then divergence of nonlinear analysis occurs rather frequently. Therefore, cable network systems do not exhibit a typical nonlinear behavior, iterative method that can handle geometric nonlinearities are necessary.

• KIEAE Journal
• /
• v.14 no.6
• /
• pp.93-97
• /
• 2014

Curtain wall system of office buildings has recently become very common in Korea. As the multi-layer curtain glazing is exposed to outdoor environment, it is very subjected to direct environmental impact. Consequently, breakage and cracks of glazing due to heat expansion is frequently observed. This study explores various causes and aspects for destruction of multi-layer glazing. A sensitivity analysis was performed on the basis that thermal changes causes damage to the multi-layer glazing. Air temperature in air cavity within the multi-layer glazing was examined to find its effect on multi-layer glazing breakage. Analysis showed high deflection to depth ratio of 1:1.8 and that higher the aspect ratio, smaller is the deflection. Allowable pressure showed that the weakest value is for aspect ratio of 1:2.9. Sensitivity analysis by the area of the glazing showed that as area of glazing becomes higher, allowable pressure and deflection-depth ratio becomes smaller. For allowable pressure and allowable deflection-depth within air cavity, the glazing breakage occurred at least $107^{\circ}C$. The results from glazing breakage by thermal factor shows that it is hard to break the glazing with only an increase in air cavity temperature in multi-layer glazing applied in buildings.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.2
• /
• pp.214-221
• /
• 2001

This paper describes the design of 3-component force/moment sensor with the force and moment ratio of wide range. It can measure the x-direction force Fx, y-direction force Fy and z-direction moment Mz simultaneously. In order to accurately measure forces and moment using 3-component force/moment sensor, it should get suitable force and moment ratio(the ratio of force Fx=200 N and moment Mz=20 Nm is ten to one), and small interference error. In this paper, in order to design the 3-component force/moment sensor with the force and moment ratio of wide range, the procedures are performed as follow : 1) the derivation of the equations to predict the bending strains on the surfaces of the plate-beams under the force or the moments, 2) the determination of the size of the sensing elements of the force/moment sensor by using the derived equations, 3) the Finite Element Method(FEM) analysis and the characteristic test for confirming the strains from the theory analysis, 4) the selection of the attachment locations of the strain gages of each sensor, 5) the analysis of the rated strain and the interference error at the attachment location of strain gages. It reveals that the rated strains calculated from the derived equations make a good agreement with the results from the Finite Element Method analysis and the characteristic test.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.1
• /
• pp.54-64
• /
• 2007

This study is a fundamental research in order to establish the design code of recycled aggregate concrete structure. The structural properties of recycled aggregate concrete such as flexure, shear, fatigue, compression, and bond development are experimentally investigated and confirmed. In this study, laboratory-scale reinforced concrete beam, column, and pull-out test specimens using recycled coarse aggregate are manufactured. Then, the structural performances of recycled aggregate concrete according to replacement ratios of recycled coarse aggregate are evaluated. Also, finite element analysis using commercial code DIANA is carried out to predict the test results and the analysis results are compared with test results in this study. Structural test results showed that the structural performances of recycled aggregate concrete specimens with 60% replacement ratio are reduced by approximately 15-20%. These results indicated that the replacement ratio of recycled coarse aggregate within 30% is a suitable to use for structural members. The results of finite element analysis showed that the specimens with 30% replacement ratio possessed similar or more excellent structural performance than normal concrete specimens. However, recycled aggregate concrete with 60% replacement ratio of recycled coarse aggregate must be carefully considered for structural applications due to significant decrease of the failure loads.

• Journal of the Korea Concrete Institute
• /
• v.29 no.1
• /
• pp.77-84
• /
• 2017

In this study, the structural performance of high strength concrete (HSC) column-normal strength concrete (NSC) slab connection was investigated according to confinement effects, aspect ratio (h/c) and strength ratio ($f^{\prime}_{cc}/f_{cs}$). The study was conducted by using finite element analysis. To verify the analysis methods, the experiments and analyses results were compared. The specimens were classified by connection types including interior column, edge column, corner column and isolated column. As a result, ultimate strength of interior column was larger than other specimens. Also, the axial stresses of connection were decreased when the aspect ratio was increased. As the strength ratio between column and slab was increased, the ultimate strength of specimens was also increased until the strength ratio was reached to 1.83.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.5
• /
• pp.3146-3152
• /
• 2014

This paper investigates the determinants for the controlling power and the concentration of the subcontracting trade between the downstream producer and the upstream supplier using a survey data for the IT industry in Gyeonggi-Do. The estimation results of the ordered logit and least square analyses are as follows. First, a firm. s controlling power across the downstream producer and the upstream supplier in the subcontracting trade would grow bigger when the company is bigger, more manufacture-oriented, and has higher ratio of export in sales. Second, the analysis for the upstream suppliers indicates that the higher dependent ratio of the subcontracting trade in the sales, the lower the concentration ratio of the R&D in the sales. Lastly, the analysis of the downstream producers indicates that the higher the dependent ratio of the subcontracting trade in the sales, the higher the concentration ratio of the R&D in the sales, which is distinctively contrast with the analysis result of the upstream suppliers. The overall estimation results are, hence, unsupporting to the transaction cost theory which predicts the increase of R&D investments in both downstream producer and upstream supplier.