• Title/Summary/Keyword: design bending moment

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The Experimental Study on the Effect of Track System on the Integral Behavior of Railway Bridge (궤도시스템이 철도교량의 정.동적거동에 미치는 영향에 관한 실험적 연구)

  • Sung, Deok-Yong;Park, Yong-Gul;Choi, Jung-Youl;Kim, Sung-Il
    • Journal of the Korean Society for Railway
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    • v.13 no.2
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    • pp.186-193
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    • 2010
  • Track system and periodic live load are characteristics of railway bridges. In the design and construction of railway bridge, periodic live load increases the importance of dynamic behavior. And It is well known that behavior of railway bridge may be affected by track system in real bridge. Through experimental study, static and dynamic behaviors were investigated. Deflection and stress due to bending moment were measured, the location of neutral axis of each section, natural frequency, damping ratio were analyzed for each three track systems - girder only, installed ballast track system and installed concrete slab track system. According to measured values for the each type of track system, concrete track system increases the stiffness of bridge by 50%, and ballast system does by 7%, dynamic responses of structure change linearly with the magnitude of load and location of neutral axis of each sections varies with each track system. Damping ratio is almost equal without and with track. Therefore, the effects of track system on the integral behaviors of railway bridge can not be ignored in the design of bridge, especially in the case of concrete slab track system. So study of the quantitative analysis method for effects of track system must be performed.

Study on Fatigue Behavior and Rehabilitation of Stringer with Coped Section(I) -Experimental Study on Static and Fatigue Behavior- (절취부를 갖는 세로보의 피로거동과 보수·보강에 관한 연구(I) -정적거동 및 피로거동의 실험적 고찰-)

  • Hwang, Yoon Koog;Chang, Dong Il
    • Journal of Korean Society of Steel Construction
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    • v.9 no.3 s.32
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    • pp.363-375
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    • 1997
  • This study encompasses the performance of static and fatigue test for the 8 large scale test specimens to clarify the fatigue behavior of coped stringer and the effect of the repair and strengthening on the damaged stringer of the floor system in steel railway bridges. For the purpose of the research, the actual stress wave for the existing bridge was measured, the basic stress range frequency histogram was made and the equivalent stress range was calculated. Using the result from the equivalent stress range made by adjusting the stress range, the static and fatigue test was carried out by identifying the previous rehabilitation and after. As the result of the static tests, it was revealed that the level of local stress under the S1 specimen test of the real equivalent stress range was similar to tensile strength of the test material, and it was consistent with the requirement of the initiation condition of the fatigue crack. Through the various rehabilitation methods to the damaged specimens, the effects of the repair and reinforcement were analyzed. According to the results of the repair of effect, bolting the high tension bolt over the stop hole was confirmed to be more adequate method than drilling only stop hole to delay the fatigue crack growth. Futhermore, in case of the stringer subjected by bending moment, the reinforcement over the upper flange side was determined to be a useful strengthening method, and the reinforcement to the web of the stringer was not appropriate to accomodate as a adequate strengthening method. Also it was confirmed that the category of the fatigue design for the coped stringer met with the category E specified on the fatigue design criteria of the Highway Standard Specification in Korea.

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Design and Structural Safety Evaluation of 1MW Class Tidal Current Turbine Blade applied Composite Materials (복합재료를 적용한 1MW급 조류 발전 터빈 블레이드의 설계와 구조 안전성 평가)

  • Haechang Jeong;Min-seon Choi;Changjo Yang
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.28 no.7
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    • pp.1222-1230
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    • 2022
  • The rotor blade is an important component of a tidal stream turbine and is affected by a large thrust force and load due to the high density of seawater. Therefore, the performance must be secured through the geometrical and structural design of the blade and the blade structural safety to which the composite material is applied. In this study, a 1 MW class large turbine blade was designed using the blade element momentum (BEM) theory. GFRP is a fiber-reinforced plastic used for turbine blade materials. A sandwich structure was applied with CFRP to lay-up the blade cross-section. In addition, to evaluate structural safety according to flow variations, static load analysis within the linear elasticity range was performed using the fluid-structure interactive (FSI) method. Structural safety was evaluated by analyzing tip deflection, strain, and failure index of the blade due to bending moment. As a result, Model-B was able to reduce blade tip deflection and weight. In addition, safety could be secured by indicating that the failure index, inverse reserve factor (IRF), was 1 or less in all load ranges excluding 3.0*Vr of Model-A. In the future, structural safety will be evaluated by applying various failure theories and redesigning the laminated pattern as well as the change of blade material.

Seismic performance assessment of single pipe piles using three-dimensional finite element modeling considering different parameters

  • Duaa Al-Jeznawi;Jitendra Khatti;Musab Aied Qissab Al-Janabi;Kamaldeep Singh Grover;Ismacahyadi Bagus Mohamed Jais;Bushra S Albusoda;Norazlan Khalid
    • Earthquakes and Structures
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    • v.24 no.6
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    • pp.455-475
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    • 2023
  • The present study investigates the non-linear soil-pile interaction using three-dimensional (3D) non-linear finite element models. The numerical models were validated by using the results of extensive pile load and shaking table tests. The pile performance in liquefiable and non-liquefiable soil has been studied by analyzing the liquefaction ratio, pile lateral displacement (LD), pile bending moment (BM), and frictional resistance (FR) results. The pile models have been developed for the different ground conditions. The study reveals that the results obtained during the pile load test and shaking cycles have good agreement with the predicted pile and soil response. The soil density, peak ground acceleration (PGA), slenderness ratio (L/D), and soil condition (i.e., dry and saturated) are considered during modeling. Four ground motions are used for the non-linear time history analyses. Consequently, design charts are proposed depended on the analysis results to be used for design practice. Eleven models have been used to validate the capability of these charts to capture the soil-pile response under different seismic intensities. The results of the present study demonstrate that L/D ratio slightly affects the lateral displacement when compared with other parameters. Also, it has been observed that the increasing in PGA and decreasing L/D decreases the excess pore water pressure ratio; i.e., increasing PGA from 0.1 g to 0.82 g of loose sand model, decrease the liquefaction ratio by about 50%, and increasing L/D from 15 to 75 of the similar models (under Kobe earthquake), increase this ratio by about 30%. This study reveals that the lateral displacement increases nonlinearly under both dry and saturated conditions as the PGA increases. Similarly, it is observed that the BM increases under both dry and saturated states as the L/D ratio increases. Regarding the acceleration histories, the pile BM was reduced by reducing the acceleration intensity. Hence, the pile BM decreased to about 31% when the applied ground motion switched from Kobe (PGA=0.82 g) to Ali Algharbi (PGA=0.10 g). This study reveals that the soil conditions affect the relationship pattern between the FR and the PGA. Also, this research could be helpful in understanding the threat of earthquakes in different ground characteristics.

Effects of Encapsulation Layer on Center Crack and Fracture of Thin Silicon Chip using Numerical Analysis (봉지막이 박형 실리콘 칩의 파괴에 미치는 영향에 대한 수치해석 연구)

  • Choa, Sung-Hoon;Jang, Young-Moon;Lee, Haeng-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.1
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    • pp.1-10
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    • 2018
  • Recently, there has been rapid development in the field of flexible electronic devices, such as organic light emitting diodes (OLEDs), organic solar cells and flexible sensors. Encapsulation process is added to protect the flexible electronic devices from exposure to oxygen and moisture in the air. Using numerical simulation, we investigated the effects of the encapsulation layer on mechanical stability of the silicon chip, especially the fracture performance of center crack in multi-layer package for various loading condition. The multi-layer package is categorized in two type - a wide chip model in which the chip has a large width and encapsulation layer covers only the chip, and a narrow chip model in which the chip covers both the substrate and the chip with smaller width than the substrate. In the wide chip model where the external load acts directly on the chip, the encapsulation layer with high stiffness enhanced the crack resistance of the film chip as the thickness of the encapsulation layer increased regardless of loading conditions. In contrast, the encapsulation layer with high stiffness reduced the crack resistance of the film chip in the narrow chip model for the case of external tensile strain loading. This is because the external load is transferred to the chip through the encapsulation layer and the small load acts on the chip for the weak encapsulation layer in the narrow chip model. When the bending moment acts on the narrow model, thin encapsulation layer and thick encapsulation layer show the opposite results since the neutral axis is moving toward the chip with a crack and load acting on chip decreases consequently as the thickness of encapsulation layer increases. The present study is expected to provide practical design guidance to enhance the durability and fracture performance of the silicon chip in the multilayer package with encapsulation layer.

Evaluation of Minimum Depth Criterion and Reinforcement Effect of the Soil Cover in a Long-span Soil-steel Bridge (장지간 지중강판구조물의 최소토피고 평가 및 토피지반 보강에 대한 수치해석)

  • 이종구;조성민;정현식;김명모
    • Journal of the Korean Geotechnical Society
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    • v.20 no.5
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    • pp.67-78
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    • 2004
  • Soil-steel bridges are made of flexible corrugated steel plates buried in the well-compacted granular soil. One kind of possible collapses of these structures could be initiated by shear or tension failure in the soil cover subjected to vehicle loads. Current design codes provide the requirements for the minimum depth of the soil cover to avoid problems associated with soil cover failures. However, these requirements were developed for short span (less than 7.7 m) structures which are made of unstiffened plates of standard corrugation (150$\times$50 m). Numerical analyses were carried out to investigate the behavior of long span soil steel bridges according to thickness of the soil cover. The span of structures were up to 20 m and deep corrugated plates (381$\times$140 m) were used. The analysis showed that the minimum cover depth of 1.5 m could be sufficient to prevent the soil cover failure in the structures with a span exceeding 10 m. Additional analyses were performed to verify the reinforcement effect of the concrete relieving slab which can be a special feature to reduce the live-load effects. Analyses revealed that the bending moment of the conduit wall with a relieving slab was less than 20% of that without a relieving slab in a case of shallow soil cover conditions.

Proposed Reduction Factor of Cyclic p-y Curves for Drilled Shafts in Weathered Soil (풍화토 지반에 근입된 현장타설말뚝의 Cyclic p-y 곡선의 감소계수 제안)

  • Kim, Byung-Chul;Jeong, Sang-Seom;Ko, Jun-Young
    • Journal of the Korean Geotechnical Society
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    • v.31 no.2
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    • pp.47-63
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    • 2015
  • A fundamental study of drilled shafts subjected to lateral cyclic loading in weathered soil was carried out based on field tests and numerical analysis. The emphasis was given on quantifying the cyclic p-y curve function from lateral cyclic loading tests and three-dimensional finite element analysis. Lateral cyclic loading tests and three-dimensional finite element analysis were carried out to investigate the behavior of drilled shafts according to the direction of cyclic loading. Based on the field tests and numerical analysis, a modified lateral load transfer relationship and design chart with degradation factors were proposed by considering the characteristics of cyclic loading. It was found that the prediction by the proposed p-y curve function is in good agreement with the general trends observed by in-situ measurements, and it represents a practical improvement in the prediction of lateral displacement and bending moment distribution of drilled shafts subjected to cyclic loading.

The Reinforcing Effect of Blade Attached Pile to Support Submerged Breakwater (보강날개로 보강된 수중잠제 지지말뚝의 보강효과 분석)

  • Jeong, Sangseom;Hong, Moonhyun;Ko, Jun
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.4
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    • pp.863-874
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    • 2015
  • The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

Lateral Behavior of Hybrid Composite Piles Using Prestressed Concrete Filled Steel Tube Piles (긴장력이 도입된 콘크리트 충전 강관말뚝을 사용한 복합말뚝의 수평거동 특성)

  • Park, No-Won;Paik, Kyu-Ho
    • Journal of the Korean Geotechnical Society
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    • v.34 no.12
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    • pp.133-143
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    • 2018
  • Concrete filled steel tube (PCFT) piles, which compose PHC piles inside thin steel pipes, were developed to increase the flexural strength of the pile with respect to the horizontal load. In order to compare the flexural strength of PCFT pile with that of steel pipe pile, several flexural tests were performed on the PCFT and steel pipe piles with the same diameter and the P-M curves for both piles were constructed by the limit state design method. Four test piles were also installed and lateral pile load tests were performed to compare the lateral load capacities and lateral behaviors of the hybrid composite piles using PCFT piles and the existing piles such as HCP and steel pipe piles. The flexural test results showed that the flexural strength of PCFT piles was 18.7% higher than that of steel pipe piles with thickness of 12mm and the same diameter, and the mid-span deflection of piles was 50% lower than that of steel pipe piles at the same bending moment. From the P-M curves, it can be seen that the flexural strength of PCFT piles subjected to the vertical load is greater than that of steel pipe piles, but the flexural strength of PCFT piles subjected to the pullout load is lower than that of steel pipe piles. In addition, field pile load tests showed that the PCFT hybrid composite pile has 60.5% greater lateral load capacity than the HCP and 35.8% greater lateral load capacity than the steel pipe pile when the length of the upper pile in hybrid composite piles was the same.

A Study on the Optimal Location of the Inclinometer and Strain Gauge in Small-Scale Underground Excavation (소규모 지하굴착에서 지중경사계와 변형률계의 최적 위치 선정에 대한 연구)

  • Gichun Kang;Jinuk Park;Byeongjin Roh;Jiahao Sun;Seong-Kyu Yun
    • Journal of the Korean Geosynthetics Society
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    • v.22 no.2
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    • pp.23-33
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    • 2023
  • Currently, there are cases in Korea where economic damage has occurred due to the ambiguity instrument installation and operation standards in the construction of temporary earth retaining wall, failing to prevent collapse of temporary earth retaining wall at the construction site in advance. Therefore, in this study, a numerical analysis was conducted to find the appropriate installation location of the inclinometer and strain gauge among the installed instruments shown in the design drawing of the temporary earth retaining wall. As a results, It was found that the installation position of the underground inclinometer is the corner of the retaining wall in the case of plane-deformation analysis, and the most displacement occurs in the center of the excavation surface in the case of 3D analysis. When the stress and moment are comprehensively analyzed, the corner is judged to be a vulnerable point. In the case of the strain gauge, In plane-deformation analysis and 3D analysis, the maximum bending stress occurred at the wale connection where the end of the strut and the counter strut are in contact. At this point, it is analyzed that it is necessary to focus on installing and managing the connection to prevent accidents from being vulnerable.