• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.3
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• pp.277-289
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• 2005

The study examines the limit strength for steel cable-stayed bridges. A case studies have been performed in order to evaluate the limit strength lot steel cable-stayed bridges using nonlinear inelastic analysis approach and bifurcation point instability analysis approach, effective tangent modulus $(E_f)$ method. To realize it, a practical nonlinear inelastic analysis condoling the initial shape is developed. In the initial shape analysis, updated structural configuration is introduced instead of initial member forces for beam-column members at every iterative step. Geometric and material nonlinearities of beam-column members are accounted by using stability function, and by using CRC tangent modulus and parabolic function, respectively Besides, geometric nonlinearity of cable members is accounted by using secant value of equivalent modulus of elasticity. The load-displacement relationships obtained by the proposed method are compared well with those given by other approaches. The limit strengths evaluated by the proposed nonlinear inelastic analysis for the proposed cable-stayed bridges with tee dimensional configuration compared with those by the inelastic bifurcation point instability analyses.

• Archives of design research
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• v.15 no.3
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• pp.259-270
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• 2002

In 1995, When people read a poem, the image that a poet intends to convey to readers shows in various colors according to the status of their emotion. Poetry is a bridge as well as a text, which connects this world and the poet's world. In such relationship, the communication through Types occurs. The realm of application of modern typography is widening due to the development of the Internet and mass media, and the ways of expression of which are changing with the help of lots of softwares. So, the modern typography is re-born as an organic language which is alive, breathing. Therefore, Types has the structural character similar to that of Typography, which is a language of image, creating today's movement, time, and space. The already existing poetry contains meanings but has a descriptive structures. On contrary, compared with the former, the type appeared in Hangul Concrete Poetry., itself is a poem in another realm due to the formality native to Hangul, and which appears in non-linear structure. So, in this thesis, I will analyze the formality and non-linear structure of Hangul Typography in order to widen the realm of research on typography, which is a very meaningful trial to visualize the literature.

• Computers and Concrete
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• v.27 no.2
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• pp.99-109
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• 2021

Experimental and discrete element methods were used to investigate the effects of echelon non-persistent joint on the failure behaviour of joint's bridge area under uniaxial compressive test. Concrete samples with dimension of 150 mm×100 mm×50 mm were prepared. Uniaxial compressive strength and tensile strength of concrete were 14 MPa and 1MPa, respectivly. Within the specimen, three echelon non-persistent notches were provided. These joints were distributed on the three diagonal plane. the angle of diagonal plane related to horizontal axis were 15°, 30° and 45°. The angle of joints related to diagonal plane were 30°, 45°, 60°. Totally, 9 different configuration systems were prepared for non-persistent joint. In these configurations, the length of joints were taken as 2 cm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increase by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Journal of Advanced Navigation Technology
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• v.28 no.3
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• pp.309-314
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• 2024

Avionics Intercom performs communication between pilot, co-pilot and crews in aircraft. In the case of developing intercom in the aircraft modification development project, additional communication equipment or avionics equipment is configured to link the existing intercom with the headsets. Newly designed intercom needs a configuration that receives an aircraft headset microphone and transmits a microphone signal to the existing intercom, and these signals are required to perform signal quality above a certain level. To satisfy these requirements, microphone transmitter circuit has designed and tested, but quality factors of signal were not suitable. In order to avoid the issue, eliminate transmitter and apply signal bridge circuit considered with load effect, and it meets requirements. In this paper, the test results for the signal quality for each configuration are reviewed.

• Structural Engineering and Mechanics
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• v.20 no.5
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• pp.543-558
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• 2005

The natural frequencies of a long span bridge vary during its construction and it is thus difficult to apply traditional tuned liquid column dampers (TLCD) with a fixed configuration to reduce bridge vibration. The restriction of TLCD imposed by frequency tuning requirement also make it difficult to be applied to structure with either very low or high natural frequency. A semi-active tuned liquid column damper (SATLCD), whose natural frequency can be altered by active control of liquid column pressure, is studied in this paper. The principle of SATLCD with adaptive tuning capacity is first introduced. The analytical models are then developed for lateral vibration of a structure with SATLCD and torsional vibration of a structure with SATLCD, respectively, under either harmonic or white noise excitation. The non-linear damping property of SATLCD is linearized by an equivalent linearization technique. Extensive parametric studies are finally carried out in the frequency domain to find the beneficial parameters by which the maximum vibration reduction can be achieved. The key parameters investigated include the distance from the centre line of SATLCD to the rotational axis of a structure, the ratio of horizontal length to the total length of liquid column, head loss coefficient, and frequency offset ratio. The investigations demonstrate that SATLCD can provide a greater flexibility for its application in practice and achieve a high degree of vibration reduction. The sensitivity of SATLCD to the frequency offset between the damper and structure can be improved by adapting its frequency precisely to the measured structural frequency.

• Wind and Structures
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• v.21 no.2
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• pp.223-239
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• 2015

Open decks are a widely used deck configuration in long-span cable-stayed bridges; however, incorporating aerodynamic countermeasures are advisable to achieve better aerodynamic performance than a bluff body deck alone. A sectional model of an open deck cable-stayed bridge with a main span of 400 m was selected to conduct a series of wind tunnel tests. The influences of five practical aerodynamic countermeasures on flutter and vortex-induced vibration (VIV) performance were investigated and are presented in this paper. The results show that an aerodynamic shape selection procedure can be used to evaluate the flutter stability of decks with respect to different terrain types and structural parameters. In addition, the VIV performance of $\prod$-shaped girders for driving comfortableness and safety requirements were evaluated. Among these aerodynamic countermeasures, apron boards and wind fairings can improve the aerodynamic performance to some extent, while horizontal guide plates with 5% of the total deck width show a significant influence on the flutter stability and VIV. A wind fairing with an angle of $55^{\circ}C$ showed the best overall control effect but led to more lock-in regions of VIV. The combination of vertical stabilisers and airflow-depressing boards was found to be superior to other countermeasures and effectively boosted aerodynamic performance; specifically, vertical stabilisers significantly contribute to improving flutter stability and suppressing vertical VIV, while airflow-depressing boards are helpful in reducing torsional VIV.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.400-408
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• 2007

In this paper, development of the 8kW parallel module converter is presented. For a effective configuration of FB-PWM converter, this paper proposes 4-parallel operation of 2 kw-module. FB converter of 2-kW module is controlled by phase shut PWM and in order to achieve ZVZCS, the simple auxiliary circuit is applied in secondary side. In order to achieve ZCS, control logic for auxiliary circuit operation is designed to reset the primary current during free-wheeling period. For output current sharing of 4-modules, the charge control is employed. The charge control logic is designed with phase shift PWM logic. Voltage controller is implemented by using DSP(TMS320LF2406) with A/D conversion data of the output current and voltage of each module. The developed converter is installed in PCU(Power Conditioning Unit) for HSG(High Speed Generator) in a vehicle and health monitoring system is implemented for vehicle operation test. Finally, performance of the developed converter is proved under practical operation of HSG.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.823-831
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• 2011

According to the development of loading equipments, it is usual to change or replace the existing stores. It has been known that pylon-mounted under stores strongly affect aircraft dynamics characteristics due to the change of aerodynamics. To predict the aerodynamics and aero-elasticity is essentially requested with considering the configuration and shape of external stores during the development of aircraft and/or external stores. In this paper, computational fluid dynamics and computational structure dynamics interaction methodology are applied for prediction of aerodynamic characteristics for F-5 aircraft's horizontal tail with various shape of external stores. FLUENT and ABAQUS were used to calculate fluid and structural dynamics. Code-bridge was made base on the globally supported radial basis function to execute interpolation and mapping. As a result, even though the aeroelasticity of the horizontal tail slightly changes according to the shape of external store, the flutter was not occurred at the considered flight conditions in this study.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.43-50
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• 2002

This paper describes a simplified numerical procedure for analyzing the response of bridge pier foundations due to riverbed scouring. A computationally efficient algorithm to analyze the behavior of a pile group is proposed by considering soil-pile, pile-cap, and pile-fluid interactions. The complex phenomenon of the pile-soil interaction is modeled by discrete nonlinear soil springs (p-y, t-z and q-z curves). The pile-cap interaction is considered by geometric configuration of the piles in a group and connectivity conditions between piles and the cap. The pile-fluid interaction is incorporated into the procedure by reducing the stiffness of the soil-pile reactions as a result of nonlinearity and degradation of the soil stiffness with river bridge scouring. Through the numerical study, it is shown that the maximum bending moment increases with increasing scour depth. Thus it is desirable to check the stability elf pile groups based on soil-pile and pile-cap interactions by considering scouring depth in the riverbed.

• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1135-1152
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• 2015

Most of current bridge decks are made of reinforced concrete and often deteriorate at a relatively rapid rate in operational environments. The quick deterioration of the deck often impacts other critical components of the bridge. Another disadvantage of the concrete deck is its high weight in long-span bridges. Therefore, it is essential to examine new materials and innovative designs using hybrid system consisting conventional materials such as concrete and steel with FRP plates which is also known as composite deck. Since these decks are relatively new, so it would be useful to evaluate their performances in more details. The present study is dedicated to Hat-Shape composite girder with concrete slab. The structural performance of girder was evaluated with nonlinear finite element method by using ABAQUS and numerical results have been compared with experimental results of other researches. After ensuring the validity of numerical modeling of composite deck, parametric studies have been conducted; such as investigating the effects of constituent properties by changing the compressive strength of concrete slab and Elasticity modulus of GFRP materials. The efficacy of the GFRP box girders has been studied by changing GFRP material to steel and aluminum. In addition, the effect of Cross-Sectional Configuration has been evaluated. It was found that the behavior of this type of composite girders can be studied with numerical methods without carrying out costly experiments. The material properties can be modified to improve ultimate load capacity of the composite girder. strength-to-weight ratio of the girder increased by changing the GFRP material to aluminum and ultimate load capacity enhanced by deformation of composite girder cross-section.