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Analysis of Performance Tests and Friction Characteristics of a Friction Type Isolator Considering Train Load Conditions (열차 하중조건을 고려한 마찰형 방진장치 성능시험 및 마찰특성 분석)

  • Koh, Yong-Sung;Lee, Chan-Young;Ji, Yong-Soo;Kim, Jae-Wang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.3
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    • pp.694-702
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    • 2017
  • In the case of an elevated railway station, structure borne noise and vibration due to structural limitations allow the load and vibration from railway vehicles to be directly transmitted to the station structure, resulting in an increase in the number of civil complaints from customers and staff of the station. The floating slab track system, which is well known as one of the solutions for reducing the noise and vibration from elevated railway stations, usually contains rubber mounts or rubber pads under the railway slab which act as a damper. These types of device have the disadvantage that is difficult to predetermine the exact stiffness and damping ratio under the nonlinear loads resulting from train services. In this study, an isolator with a friction type of wedge is introduced, which can be applied to floating slab track systems and to be designed with precisely the required stiffness. Furthermore, a comparative analysis of the stiffness between the designed and experimental values is carried out, while the damping ratio, which is closely related to the friction wedge blocks, is deduced according to the train load condition. The performance tests of the isolator were conducted in accordance with the DIN 45673-7 standard which includes both static and dynamic load tests. The load conditions for the performance tests are designed to conform to the DIN standard related to the weight of the train and rail track, in order to perform vertical and horizontal load tests, so as to ensure the secure structural safety of the railway. Also, by checking the change aspect of the friction coefficients of the friction elements according to the loading rate, the vibration reduction performance of the friction type isolator with variable loading rate conditions is examined.

Shear Resistance of Unreinforced Cast-In-Place Anchors in Uncracked and Cracked Concrete by Seismic Qualification Tests (지진모의실험에 의한 비균열 및 균열콘크리트에 매입된 비보강 선설치앵커의 전단 저항강도 평가)

  • Park, Yong Myung;Kim, Tae Hyung;Kim, Dong Hyun;Jo, Sung Hoon;Lee, Jong Han
    • Journal of Korean Society of Steel Construction
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    • v.27 no.3
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    • pp.347-357
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    • 2015
  • In this study, an experimental study was performed to evaluate the concrete breakout strength of unreinforced cast-in-place anchors by seismic qualification test under shear loading. The CIP anchors tested herein were 30mm in diameter with an edge distance of 150mm and an embedment depth of 240mm in uncracked and cracked concrete. The cracked specimen consisted of orthogonal and parallel crack to the loading direction, respectively. The dynamic loading sequence during the seismic qualification test was determined based on CSA N287.2, ACI 355.2 and ETAG 001 codes. After the dynamic loading, the static loading was applied until failure occurs. The shear resistance by seismic qualification tests showed almost the same strength as that obtained from the static tests in uncrcaked and cracked concrete, respectively. Meanwhile, the breakout depth did not reach $8d_0$, therefore the modified strength equation of ACI 318-11 could estimate properly the concrete breakout strength, which does not consider effective bearing length.

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.

Pseudo-Static Behaviors of U-shaped PSC Girder with Wide Flanges (확폭플랜지를 갖는 U형 프리스트레스 거더의 유사정적거동)

  • Rhee, In-Kyu;Lee, Joo-Beom;Kim, Lee-Hyeon;Park, Joo-Nam;Kwak, Jong-Won
    • Proceedings of the KSR Conference
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    • 2008.11b
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    • pp.993-999
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    • 2008
  • A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

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Development of Impact Factor Response Spectrum with Tri-Axle Moving Loads and Investigation of Response Factor of Middle-Small Size-RC Slab Aged Bridges (3축 이동하중을 고려한 충격계수 응답스펙트럼 개발 및 중소규모 RC 슬래브 노후교량 응답계수 분석)

  • Kim, Taehyeon;Hong, Sanghyun;Park, Kyung-Hoon;Roh, Hwasung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.67-74
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    • 2019
  • In this paper the response factor is investigated for middle and small size-RC slab aged bridges. The response factor consists of static and dynamic response factors and is a main parameter in the frequency based-bridge load carrying capacity prediction model. Static and dynamic response factors are determined based on the frequency variation and the impact factor variation respectively between current and previous (or design) states of bridges. Here, the impact factor variation is figured out using the impact factor response spectrum which provides the impact factor according to the natural frequency of bridges. In this study, four actual RC slab bridges aged over 30 years after construction are considered and their span length is 12m. The dynamic loading test in field using a dump truck and eigenvalue analysis with FE models are conducted to identify the current and previous (or design) state-natural frequencies of the bridges, respectively. For more realistic considerations in the moving loading situation, the impact factor response spectrum is developed based on tri-axle moving loads representing the dump truck load distribution and various supporting conditions such as simply supported and both ends fixed conditions. From the results, the response factor is widely ranged from 0.21to 0.91, showing that the static response factor contributes significantly on the results while the dynamic response factor has a small effect on the result. Compared to the results obtained from the impact factor response spectrum based on the single axle-simply supported condition, the maximum percentage difference of the response factors is below 3.2% only.

Assessment of p-y Behaviors of a Cyclic Laterally Loaded Pile in Saturated Dense Silty Sand (조밀한 포화 실트질 모래지반에서 횡방향 반복하중을 받는 말뚝의 p-y 거동 평가)

  • Baek, Sung-Ha;Choi, Changho;Cho, Jinwoo;Chung, Choong-Ki
    • Journal of the Korean Geotechnical Society
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    • v.35 no.11
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    • pp.97-110
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    • 2019
  • Piles that support offshore wind turbine structures are dominantly subjected to cyclic lateral loads of wind, waves, and tidal forces. For a successful design, it is imperative to investigate the behavior of the cyclic laterally loaded piles; the p-y curve method, in which the pile and soil are characterized as an elastic beam and nonlinear springs, respectively, has been typically utilized. In this study, model pile tests were performed in a 1 g gravitational field so as to investigate the p-y behaviors of cyclic laterally loaded piles installed in saturated dense silty sand. Test results showed that cyclic lateral loads gradually reduced the overall stiffness of the p-y curves (initial stiffness and ultimate soil reaction). This is because the cyclic lateral loads disturbed the surrounding soil, which led to the decrement of the soil resistance. The decrement effects of the overall stiffness of the p-y curves became more apparent as the magnitude of cyclic lateral load increased and approached the soil surface. From the test results, the cyclic p-y curve was developed using a p-y backbone curve method. Pseudo-static analysis was also performed with the developed cyclic p-y curve, confirming that it was able to properly predict the behaviors of cyclic laterally loaded pile installed in saturated dense silty sand.

Fatigue Behavior of Prestressed Concrete Beams Using FRP Tendons (FRP 긴장재를 이용한 프리스트레스트 콘크리트 보의 피로 거동)

  • Kim, Kyoung-Nam;Park, Sang-Yeol;Kim, Chang-Hoon
    • Journal of the Korea Concrete Institute
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    • v.23 no.2
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    • pp.135-144
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    • 2011
  • Recently, researches about fiber reinforced polymer (FRP) which has excellent durability, corrosion resistance, and tensile strength as a substitution material to steel tendon have been actively pursued. This study is performed to examine FRP tendon used prestressed beam's safety under service load. The specimen was a prestressed concrete beam with internal bonded FRP tendon. In order to compare the member fatigue capacity, a control specimen of a prestressed concrete beam with ordinary steel tendon was tested. A fatigue load was applied at a load range of 60%, 70%, and 80% of the 40% ultimate load, which was obtained though a static test. The fatigue load was applied as a 1~3 Hz sine wave with 4 point loading setup. Fatigue load with maximum 1 million cycles was applied. The specimen applied with a load ranging between 40~60% did not show a fatigue failure until 1 million cycles. However, it was found that horizontal cracks in the direction of tendons were found and bond force between the tendon and concrete was degraded as the load cycles increased. This fatigue study showed that the prestressed concrete beam using FRP tendon was safe under a fatigue load within a service load range. Fatigue strength of the specimen with FRP and steel tendon after 1 million cycles was 69.2% and 59.8% of the prestressed concrete beam's static strength, respectively.

Representation of Dynamic Stiffness Matrix with Orthogonal Polynomials (직교다항식을 이용한 구조계의 축약된 동강성행렬 표현)

  • 양경택;최계식
    • Computational Structural Engineering
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    • v.6 no.2
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    • pp.95-102
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    • 1993
  • A modeling method is described to provide a smaller structural dynamic model which can be used to compare finite element model of a structure with its experimental counterpart. A structural dynamic model is assumed to be represented by dynamic stiffness matrix. To validate a finite element model, it is often necessary to condense a large degrees of freedom (dofs) to a relatively small number of dofs. For these purpose, static reduction techniques are widely used. However, errors in these techniques are caused by neglecting frequency dependent terms in the functions relating slave dofs and master dofs. An alternative method is proposed in this paper in which the frequency dependent terms are considered by expressing the reduced dynamic stiffness matrix with orthogonal polynomials. The reduced model has finally a minimum set of dofs, such as sensors and excitation points and it is under the same condition as the physical system. It is proposed that the reduced model can be derived from finite element model. The procedure is applied to example structure and the results are discussed.

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Load-carrying Capacity of Thermal Prestressed Steel Beam with Eccentric Bracket (편심 브라켓 설치 온도프리스트레싱 강재보의 하중저항 성능)

  • Kim, Sang-Hyo;Jung, Chi-Young;Choi, Kyu-Tae;Ahn, Jin-Hee
    • Journal of Korean Society of Steel Construction
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    • v.22 no.6
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    • pp.563-572
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    • 2010
  • This study evaluates the load-carrying capacity of a thermal prestressed steel beam with an eccentric bracket. The steel beam that is proposed in this study has an eccentrically installed cover plate through application of the eccentric bracket. The eccentric bracket helps the steel beam achieve greater sectional stiffness and more efficiently induces prestress. A material non-linear characteristic applied finite element analysis was also conducted to check the validity of the experiments. The results of this study showed that the structural stiffness, yield load, and ultimate strength of the TPSM-applied steel beam with the eccentric bracket increased due to the eccentricity of the cover plate.

Flexural Behavior Characteristics of Steel I-Beam Strengthened by the Post-tensioning Method on the Field Experiment (현장실험을 통한 외부 후긴장 Steel I-Beam의 휨 거동 특성)

  • Cho, Doo-Yong;Park, Dae-Yul;Park, Sun-Kyu
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.6 no.3
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    • pp.151-158
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    • 2002
  • Recently, the externally prestressed unbonded steel I-beam bridges have been increasingly built. The mechanical behavior of prestressed steel I-beams which are with external unbonded tendon is different from that of normal bonded PSC beams in a point of that the slip of tendons at deviators and the change of tendon eccentricity occurs, when external loads are applied in external unbonded steel I-beams. The concept of prestressing steel structures has not been widely considered, in spite of long and successful history of prestressing concrete members. In this study, The field experiment on prestressed steel I-beams has been performed in the various aspects of prestressed I-beam including the tend on type and profile.