• Title/Summary/Keyword: scaled model tests

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A Statistical Approach for the Size Effect on the Strength of CFRP (탄소섬유 복합재의 강도 크기효과에 관한 통계적 접근)

  • Hwang, Tae-Kyeong;Kim, Hyung-Kun;Kim, Seong-Eun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.472-476
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    • 2011
  • This paper presents the results of theoretical analysis and experimental test to verify the size effect on the fiber strength of filament wound pressure vessel. As a test method, a series of fully scaled hoop ring tests with filament wound carbon fiber-epoxy has been conducted. Test results showed remarkable size effect on fiber strength. And, as an analytical method, the WWLM(Weibull weakest link model) and SMFM(sequential multi-step failure model) were considered and compared to hoop ring test data. The analysis results showed significantly lower fiber strength value than that of test data. Through the modification of length size effect, modified SMFM is suggested. The fiber strengths from modified SMFM showed good agreement with test data.

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Dynamic Response Analysis of Caisson Structure by Acceleration Measurement (가속도 계측을 통한 항만시설용 케이슨 구조체의 동적응답 분석)

  • Lee, So-Young;Kim, Jeong-Tae;Kim, Heon-Tae;Park, Woo-Sun
    • Journal of Ocean Engineering and Technology
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    • v.23 no.1
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    • pp.114-121
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    • 2009
  • In this study, acceleration responses of caisson structures under various environmental conditions are experimentally examined as a basic study to develop the health assessment technique for harbor structures. To achieve the objective, three approaches are implemented. Firstly, a target caisson structure is selected and its small-scaled caisson is constructed in the laboratory. Secondly, a finite element model of the caisson is generated to identify dynamic responses of the baseline structure. Thirdly, experimental tests are performed on the caisson model to examine dynamic responses under various boundary conditions and impact locations. Four different boundary conditions, 'standing on concrete floor', 'standing on styrofoam block', 'standing on sand-mat' and 'hanging by crane', are considered and correlation coefficients of frequency response functions between four states are analyzed.

Size effect on tensile strength of filament wound CFRP composites (필라멘트 와인딩 탄소섬유 복합재의 인장강도 크기 효과)

  • Hwang, T.K.;Doh, Y.D.;Kim, H.G.
    • Composites Research
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    • v.24 no.5
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    • pp.1-8
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    • 2011
  • This paper presents the results of theoretical analysis and experimental test to show the size effect on the fiber strength of filament would pressure vessel. First, a series of fully scaled hoop ring tests with filament would carbon-epoxy were conducted, which exhibited a remarkable size effect on the fiber strength. Next, the failure analyses using WWLM(Weibull Weakest Link Model) and the SMFM(Sequential Multi-step Failure Model) were performed and compared to the hoop ring test data, as well as to unidirectional specimens test data from the literature. It was found that the analysis results significantly underestimated the fiber strengths compared to the test data. In this study, a modified SMFM was proposed through the modification of the length size effect. The fiber strengths from modified SMFM analysis showed good agreement with the test data.

The Evaluation on Behavior of Segmental Grid Retaining Wall by Model Test (압밀주입에 의한 지반개량 특성고찰)

  • Kim, Sang-Su;Bae, Woo-Seok;Lee, Jong-Kyu
    • 기술발표회
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    • s.2006
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    • pp.162-171
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    • 2006
  • Segmental Grid Retaining Wall is one of the segmental grid retaining walls using headers and stretchers to establish the framework of the wall In this method, grids formed by the intersection of headers and stretchers are generally filled with the gravel to maintain the weight of the wall Therefore, the construction can be carried out with higher speed and much economically when compared with the concrete retaining wall Furthermore, it has high drain capacity, and environmentally friendly aspects also have been pointed out because the possibility of the planting at the front of the wall However, in the segmental grid retaining wall method, the relative movement between the individual headers and stretchers was generally recognized, and stress redistribution in the gravel filling was also observed when subjected to the external loading and self-weight of filling Therefore, it has been thought that the distribution of the earth pressure in the segmental grid retaining wall system differ from that of the concrete retaining wall In this study, the surcharge tests using the scaled model segmental grid retaining wall was carried out to observe the distribution of the earth pressure in the segmental grid retaining wall The earth pressure was measured in the six specified height of wall, and the distribution of the pressure was analyzed. Furthermore, the earth pressure by computation or by the test using the concrete retaining wall was also considered to make comparison

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Measurement of aerodynamic coefficients of tower components of Tsing Ma Bridge under yaw winds

  • Zhu, L.D.;Xu, Y.L.;Zhang, F.;Xiang, H.F.
    • Wind and Structures
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    • v.6 no.1
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    • pp.53-70
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    • 2003
  • Tsing Ma Bridge in Hong Kong is the longest suspension bridge in the world carrying both highway and railway. It has two H-shape concrete towers, each of which is composed of two reinforced concrete legs and four deep transverse prestressed concrete beams. A series of wind tunnel tests have been performed to measure the aerodynamic coefficients of the tower legs and transverse beams in various arrangements. A 1:100 scaled 3D rigid model of the full bridge tower assembled from various tower components has been constructed for different test cases. The aerodynamic coefficients of the lower and upper segments of the windward and leeward tower legs and those of the transverse beams at different levels, with and without the dummy bridge deck model, were measured as a function of yaw wind angle. The effects of wind interference among the tower components and the influence of the bridge deck on the tower aerodynamic coefficients were also investigated. The results achieved can be used as the pertinent data for the comparison of the computed and field-measured fully coupled buffeting responses of the entire bridge under yaw winds.

Theoretical and Experimental Studies on Dynamic Behavior of a Damaged Ship in Waves (파랑중 손상선박의 거동에 관한 이론적 실험적 연구)

  • Lee, Dong-Kon;Hong, Sa-Young;Lee, Gyeong-Joong
    • Journal of the Society of Naval Architects of Korea
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    • v.43 no.1 s.145
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    • pp.1-14
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    • 2006
  • To improve maritime safety, it is very important not only to make safer design and operation but also to do proper response in case of maritime casualty. The large-scaled casualties will be caused by loss of structural strength and stability due to the progressive flooding and enlargement of damage by the effect of waves and wind. To prevent foundering and structural failure, the prediction of ship motion behavior of damaged ship in wave is necessary. This paper describes the motion behavior of damaged ship in waves through theoretical and experimental studies. A time domain theoretical model of damaged ship motions and accidental flooding, which can be applied to any type of ship or arrangement and considers the effects of flooding of compartments, has been developed. The model tests have been carried out in regular and irregular waves with different wave heights and directions in ship motion basin. Those were performed for three different damaged conditions such as engine room bottom damage, side shell damage and bow visor damage of a Ro-Ro ship. Comparison of theoretical and experimental results was performed.

Evaluation of Seakeeping Performance for an Amphibious Vehicle in Regular Head Waves Using Scaled Model (축소 모형을 활용한 선수 규칙파 중 수륙양용장갑차의 내항 성능 평가)

  • Youngmin Heo;Myungjun Jeon;Hyeon Kyu Yoon
    • Journal of the Society of Naval Architects of Korea
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    • v.61 no.2
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    • pp.77-87
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    • 2024
  • In the present study, seakeeping performance for an amphibious vehicle in regular head waves was analyzed and evaluated experimentally and numerically. First, seakeeping tests were performed to confirm the vehicle's motion response of heave, pitch motion and vertical acceleration in restricted wavelength ratio conditions for a simplified vehicle shape. Numerical analyses were also conducted for a simplified vehicle shape to validate the numerical solver. To simulate the vehicle's motions, multi-degrees of freedom were calculated by a dynamic fluid-body interaction solver in STAR-CCM+. Comparison between numerical and experimental results was carried out for a simplified vehicle shape. Numerical results are in good agreement with experimental results. Second, numerical analyses were performed for a detailed vehicle shape considering seaway wavelength conditions. The seakeeping performance for an amphibious vehicle was evaluated by comparing with the existing ship's seakeeping performance standards.

Experimental research on design wind loads of a large air-cooling structure

  • Yazhou, Xu;Qianqian, Ren;Guoliang, Bai;Hongxing, Li
    • Wind and Structures
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    • v.28 no.4
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    • pp.215-224
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    • 2019
  • Because of the particularity and complexity of direct air-cooling structures (ACS), wind parameters given in the general load codes are not suitable for the wind-resistant design. In order to investigate the wind loads of ACS, two 1/150 scaled three-span models were designed and fabricated, corresponding to a rigid model and an aero-elastic model, and wind tunnel tests were then carried out. The model used for testing the wind pressure distribution of the ACS was defined as the rigid model in this paper, and the stiffness of which was higher than that of the aero-elastic model. By testing the rigid model, the wind pressure distribution of the ACS model was studied, the shape coefficients of "A" shaped frame and windbreak walls, and the gust factor of the windbreak walls were determined. Through testing the aero-elastic model, the wind-induced dynamic responses of the ACS model was studied, and the wind vibration coefficients of ACS were determined based on the experimental displacement responses. The factors including wind direction angle and rotation of fan were taken into account in this test. The results indicated that the influence of running fans could be ignored in the structural design of ACS, and the wind direction angle had a certain effect on the parameters. Moreover, the shielding effect of windbreak walls induced that wind loads of the "A" shaped frame were all suction. Subsequently, based on the design formula of wind loads in accordance with the Chinese load code, the corresponding parameters were presented as a reference for wind-resistant design and wind load calculation of air-cooling structures.

CFD Analysis on Base Region of Small Scaled 4 Nozzle Clustered Engine Configuration (CFD를 이용한 축소형 공기 클러스터드 노즐의 저부 유동 분석)

  • Kim, Seong-Lyong;Kim, In-Sun
    • Aerospace Engineering and Technology
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    • v.11 no.1
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    • pp.68-77
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    • 2012
  • Flow characteristics of base region of small scaled 4 nozzle clustered engine has been analyzed with CFD approach along with the tests of numerical methods. The numerical test shows that Spalart-Allmaras turbulence model is appropriate for the present research. Plumes expanded from nozzles exits collide with each other and make high pressure stagnation region. Some of collided plumes expand again reversely into the base region with supersonic speeds. The reversed plume in the base region goes out to the outer region through the minimum vent area formed by the nearest nozzle exterior surfaces. But different from the empirical theory, the minimum vent area does not play a role of throat. Additionally the temperature of the nozzle inner surface strongly affects the temperature of the reversed plumes.

Real-time Vibration Control of Cable Bridges using a Shear-type MR Damper-Focusing on Power Model and Lyapunov Control (전단형 MR 댐퍼를 이용한 케이블 교량의 실시간 진동제어-파워 모델 및 리야프노브 제어 중심으로)

  • Heo, Gwanghee;Lee, Chinok;Jeon, Seunggon;Kim, Chunggil;Jeon, Joonryong
    • Journal of the Earthquake Engineering Society of Korea
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    • v.21 no.5
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    • pp.215-226
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    • 2017
  • In this paper, an experimental study was carried out for vibration control of cable bridges with structurally flexible characteristics. For the experiment on vibration control, a model bridge was constructed by reducing the Seohae Grand Bridge and the shear type MR damper was designed using the wind load response measured at Seohae Grand Bridge. The shear type MR damper was installed in the vertical direction at the middle span of the model bridge, and dynamic modeling was performed using the power model. The tests of the vibration control were carried out by non-control, passive on/off control and Lyapunov control method on model bridge with scaled wind load response. The performance of the vibration control was evaluated by calculating absolute maximum displacement, RMS displacement, absolute maximum acceleration, RMS acceleration, and size of applied power using the response (displacement, acceleration, etc.) from the model bridge. As a result, the power model was effective in simulating the nonlinear behavior of the MR damper, and the Lyapunov control method using the MR damper was able to control the vibration of the structure and reduce the size of the power supply.