• Title/Summary/Keyword: load-displacement

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Calculation of Deflection Using the Acceleration Data for Concrete Bridges (가속도 계측 자료를 이용한 콘크리트 교량의 처짐 산정)

  • Yun, Young Koun;Ryu, Hee Joong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.5
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    • pp.92-100
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    • 2011
  • This paper describes a numerical modeling for deflection calculation using the natural frequency response that is measured acceleration response for concrete bridges. In the formulation of the dynamic deflection, the change amounts and the transformed responses about six kinds of free vibration responses are defined totally. The predicted response can be obtained from the measured acceleration data without requiring the knowledge of the initial velocity and displacement information. The relationship between the predicted response and the actual deflection is derived using the mathematical modeling that is induced by the process of a acceleration test data. In this study, in order to apply the proposed response predicted model to the integration scheme of the natural frequency domain, the Fourier Fast Transform of the deflection response is separated into the frequency component of the measured data. The feasibility for field application of the proposed calculation method is tested by the mode superposition method using the PSC-I bridges superstructures under several cases of moving load and results are compared with the actually measured deflections using transducers. It has been observed that the proposed method can asses the deflection responses successfully when the measured acceleration signals include the vehicle loading state and the free vibration behavior.

Characteristics of Shear Behavior of Reinforced Concrete Beams Strengthened with Near Surface Mounted CFRP Strips (CFRP 스트립 표면매립공법으로 보강된 철근콘크리트 보의 전단거동 특성)

  • Han, Sang Hoon;Hong, Ki Nam;Shin, Byoung Gil;Lim, Jin Mook;Kwak, So Shin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.5
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    • pp.178-189
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    • 2011
  • Tests and analyses were performed in this study to assess the shear strength of Reinforced Concrete(RC) members strengthened by the Near Surface Mounted(NSM) technique in shear, which is drawing attention as an alternative to the Carbon Fiber Reinforced Polymer(CFRP) bonding strengthening technique. Four-point bending tests were performed on 7 RC specimens without any shear reinforcement. The test variables such as the inclination of CFRP strip (45 degrees and 90 degrees), and the spacing of CFRP strip (250mm, 200mm, 150mm, 100mm) were considered. Through the testing scenarios, the effect of each test variable on the failure mode and the shear strength of the RC members strengthened by the NSM technique in shear were assessed. The test results show that the specimens with CFRP strips at 45 degrees go to failure as a result of the strip fracture, but the specimens with CFRP strips at 90 degrees go to failure as a result of the slip of strips. Strips at 45 degrees was the more effective than strips at 90 degrees, not only in terms of increasing beam shear resistance but also in assuring larger deformation capacity at beam failure. In addition, the RBSN analysis appropriately predicted the crack formation and the load-displacement response of the RC members strengthened by the NSM technique in shear.

Dynamic Response of PSC I shape girder being used wide upper flange in Railway Bridge (확장된 상부플랜지 PSC I형 거더교의 동특성 및 동적안정성 분석)

  • Park, Jong-Kwon;Jang, Pan-Ki;Cha, Tae-Gweon;Kim, Chan-Woo;Jang, Il-Young
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.4
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    • pp.125-135
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    • 2015
  • The tendency of more longer span length being required economical in railway bridges is studying about PSC I shaped girder. In this case, it is important to analyze and choose the effective girder section for stiffness of bridge. This study investigates the dynamic properties and safety of PSC I shaped girder being used wide upper flange whose selection based on radii and efficiency factor of flexure for railway bridge in different span type. In addition, 40m PSC Box girder bridge adopted in Honam high speed railway is further analyzed to compare dynamic performance of PSC I shaped girder railway bridge with same span length. Time history response is acquired based on the mode superposition method. Static analysis is also analyzed using standard train load combined with the impact factor. Consequently, the result met limit values in every case including vertical displacement, acceleration and distort.

Evaluation of Uplift Forces Acting on Fastening Systems at the Bridge Deck End Considering Nonlinear Behaviors of the Fastening Systems (체결장치 비선형 거동을 고려한 교량 단부에서의 체결장치 압상력 평가)

  • Yang, Sin Chu;Kim, Hak Hyung;Kong, Jung Sik
    • Journal of the Korean Society for Railway
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    • v.20 no.4
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    • pp.521-528
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    • 2017
  • In this study, vertical loading tests were conducted to investigate the nonlinear behaviors of the fastening systems that have generally been used in the concrete track of domestic railway lines. Nonlinear load-displacement curve models were derived based on the test results. The uplift forces generated in the fastening systems were evaluated by applying the derived nonlinear models as well as the existing linear models. The influence of the factors on the maximum uplift force of the fastening system was analyzed through a parameter study on the distance between neighboring sleepers, the horizontal distance between the center of the bearing and the nearest fastening system from the deck end, and the height of the bridge girder. From the evaluation results it is known that, for economical track and bridge design, due to deck end deformation, it is necessary to consider the nonlinear behavior of the fastening system in the calculation of the uplift force of the fastening systems.

Performance Evaluation of RC Slabs Strengthened by Stiff Type PolyUrea (경질형 폴리우레아로 보강된 RC 슬래브의 성능 평가)

  • Park, Jeong Cheon;Lee, Sang Won;Kim, Sung Bae;Kim, Jang-Ho Jay
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.6A
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    • pp.457-464
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    • 2011
  • An experimental study was performed to evaluate the possibility of using stiff type PolyUrea(PU) on RC slab as a strengthening material. Stiff type PU(STPU) was sprayed on the bottom surface of the slab specimens, which were then attached with CFRP or GFRP sheets. Also the evaluation of the bond capacity, the single most influential parameter on strengthening of RC structures, was carried out the flexural capacity evaluation test results showed that the load carrying capacity of the PU specimen was greater and less than the unstrengthened and FRP sheet attached specimens, respectively. The STPU specimens showed a ductile flexural behavior in the plastic displacement range. With respect to bond capacity, the bond strength of all of the specimen exceeded the code required bond strength of 1.5 MPa. Also, the STPU sprayed specimen without using epoxy resin did not peel off when the tensile grip was applied for testing. The stability of the PU bond failure indicate a good bond strength of PU when applied to concrete.

Nonlinear Lateral Behavior and Cross-Sectional Stress Distribution of Concrete Rocking Columns (콘크리트 회전형 기둥의 비선형 횡방향 거동 및 단면응력 분포 분석)

  • Roh, Hwa-Sung;Hwang, Woong-Ik;Lee, Hu-Seok;Lee, Jong-Seh
    • Journal of the Korea Concrete Institute
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    • v.24 no.3
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    • pp.285-292
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    • 2012
  • Fixed connection is generally used for beam and column connections of concrete structures, but significant damages at the connection due to severe earthquakes have been reported. In order to reduce damages of the connection and improve seismic performance of the connection, several innovative connections have been suggested. One newly proposed connection type allows a rotation of the connection for applications in rotating or rocking beams, columns, and shear walls. Such structural elements would provide a nonlinear lateral force-displacement response since their contact depth developed during rotation is gradually reduced and the stress across the sections of the elements is non-linearly distributed around a contact area, which is called an elastic hinge region in the present study. The purpose of the present study is to define the elastic hinge region or length for the rocking columns, through investigating the cross-sectional stress distribution during their lateral behavior. Performing a finite element analysis (FEA), several parameters are considered including axial load levels (5% and 10% of nominal strength), different boundary conditions (confined-ends and cantilever types), and slenderness ratios (length/depth = 5, 7, 10). The FEA results showed that the elastic hinge length does not directly depend on the parameters considered, but it is governed by a contact depth only. The elastic hinge length started to develop after an opening state and increased non-linearly until a rocking point(pre-rocking). However, the length did not increase any more after the rocking point (post-rocking) and remained as a constant value. Half space model predicting the elastic hinge length is adapted and the results are compared with the numerical results.

Experimental Evaluation of Bi-directionally Unbonded Prestressed Concrete Panel Blast Resistance Behavior under Blast Loading Scenario (폭발하중 시나리오에 따른 2방향 비부착 프리스트레스트 콘크리트 패널부재의 폭발저항성능에 대한 실험적 거동 평가)

  • Choi, Ji-Hun;Choi, Seung-Jai;Cho, Chul-Min;Kim, Tae-Kyun;Kim, Jang-Ho Jay
    • Journal of the Korea Concrete Institute
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    • v.28 no.6
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    • pp.673-683
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    • 2016
  • In recent years, frequent terror or military attack by explosion, impact, fire accidents have occurred. Particularly, World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. Also, nuclear power plant incident on Mar. 11 of 2011. These attacks and incidents were raised public concerns and anxiety of potential terrorist attacks on major infrastructures and structures. Therefore, the extreme loading researches were performed of prestressed concrete (PSC) member, which widely used for nuclear containment vessel and gas tank. In this paper, to evaluate the blast resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, blast tests were carried out on $1,400{\times}1,000{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PSC), prestressed concrete with rebar (PSRC) specimens. The applied blast load was generated by the detonation of 55 lbs ANFO explosive charge at 1.0 m standoff distance. The data acquisitions not only included blast waves of incident pressure, reflected pressure, and impulse, but also included displacement, acceleration, and strains at steel, concrete, PS tendon. The results can be used as basic research references for related research areas, which include protective design and blast simulation under blast loading.

Inelastic Nonlinear Analysis of Arch Truss and Space Truss Structures (아치 트러스 및 공간 트러스 구조의 비탄성 비선형 거동해석)

  • Kim, Kwang-Joong;Jung, Mi-Roo;Kim, Yeon-Tae;Baek, Ki-Youl;Lee, Jae-Hong
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.5
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    • pp.47-58
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    • 2008
  • Spatial structure is an appropriate shape that resists external force only with in-plane force by reducing the influence of bending moment, and it maximizes the effectiveness of structural system. With this character of the spatial structure, generally long span is used. As a result, large deflection is accompanied from the general frame. the structure is apt to result in a large deflection even though this structure experiences a small displacement in absence. Usually, nonlinear analysis in numerical analysis means geometric nonlinearity and material nonlinearity and complex nonlinearity analysis considers both of them. In this study, nonlinear equation of equilibrium considering geometric nonlinearity as per finite element method was applied and also considered the material nonlinearity using the relation of stress-strain in element. It is applied to find unstable result for tracing load-deflection curve in the numerical analysis tech. especially Arc-length method, and result of the analysis was studied by ABAQUS a general purpose of the finite element program. It is found that the present analysis predicts accurate nonlinear behavior of plane and space truss.

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Simulation and Experimental Investigation of Reverse Drawing Process for Manufacture of High-Capacity Aluminum Liner (대용량 알루미늄 라이너의 성형을 위한 역 드로잉 공정 해석 및 실험)

  • Lee, Seungyun;Cho, Sungmin;Lee, Sunkyu;Lyu, Geunjun;Kim, Soyoung;Kang, Sunghun
    • Journal of the Korean Institute of Gas
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    • v.20 no.4
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    • pp.78-84
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    • 2016
  • In this work, finite element investigations were carried out to optimize reverse drawing process design for manufacture of high-capacity aluminum liner used in fuel cell vehicle. The tensile tests with aluminum alloy Al6061 annealed at $350^{\circ}C$ were carried out to obtain the flow stresses. In order to estimate more accurate flow stresses after necking, the flow stresses were estimated from the comparison of load vs. displacement curves which were obtained from experimental and simulation results of tensile tests. In case of finite element analyses of reverse drawing processes, it was focused on the effects of process designs such as punch and die designs, blank holding force, drawing ratio and the clearance between the punch and blank holder on the generation of wrinkle and fracture of the blank and partially heated punch. However, it was revealed that experimental results still show the fracture at the end of 2nd drawn cup, although partially heated punch is used. Nevertheless, the drawn cup can be used because the sufficient length of the drawn cup for the next flow forming process and spinning process was obtained.

Seismic Behavior and Economic efficiency Analysis of Bridge for PSC I-Shaped Girder of isolated device (지진격리장치를 갖는 PSC I형 거더교량의 지진거동 특성 및 경제성 분석)

  • Shin, Yung-Seok;Park, Jang-Ho;Choi, Kwang-Soo;Hong, Soon-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.21 no.2
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    • pp.145-151
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    • 2008
  • The research so far has primarily analyzed efficiency improvement but in this research, it analyzes the characteristics of earthquake behavior, with changed pier heights, through ordinary and seismic analysis. For this, the kind of bridge bearing has been changed against PSC I-shaped bridge, which is mostly used in practice, and at all times earthquake analysis has been performed with through height of pier. Especially considering sectional power resulting from earthquake analysis, displacement of PSC I-shaped bridge bearing, diameter of pier pillar by earthquake load, and upper spare gap have been analyzed. In case of high-pear, seismic isolated device is decided as proper for cars' driving and for management of bridge since it decreases movement of upper structure, than elastic bearing, reducing size of elastic connect device, and it's been analyzed it is effective for improvement of fine view and economic efficiency reducing section of lower bridge structure. Finally, when design PSC I-shaped bridge bearing, for the proper structure and high-pier side, applying seismic isolated device through precise inner analysis is proper than applying equal elastic bearing.