• Title/Summary/Keyword: Load carrying

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Dynamic Change of Stresses in Subsoil under Concrete Slab Track Subjected to Increasing Train Speeds (열차 증속에 따른 콘크리트 궤도 노반의 동적 응력 변화)

  • Lee, Tae-Hee;Choi, Chan-Yong;Nsabimana, Ernest;Jung, Young-Hoon
    • Journal of the Korean Geotechnical Society
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    • v.29 no.10
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    • pp.57-66
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    • 2013
  • Societal interest on a faster transportation demands an increase of the train speed exceeding current operation speed of 350 km/h. To trace the pattern of variations in displacements and subsoil stresses in the concrete slab track system, finite element simulations were conducted. For a simple track-vehicle modeling, a mass-point system representing the moving train load was developed. Dynamic responses with various train speeds from 100 to 700 km/h were investigated. As train speeds increase the displacement at rail and subsoil increases nonlinearly, whereas significant dynamic amplification at the critical velocity has not been found. At low train speed, the velocity of elastic wave carrying elastic energy is faster than the train speed. At high train speed exceeding 400 km/h, however, the train speed is approximately identical to the elastic wave velocity. Nonlinearity in the stress history in subsoil is amplified with increasing train speeds, which may cause significant plastic strains in path-dependent subsoil materials.

Lubrication Analysis of Infinite Width Slider Bearing with a Micro-Groove: Part 3 - Effect of Groove Shape (미세 그루브가 있는 무한폭 Slider 베어링의 윤활해석: 제3보 - 그루브 형상의 영향)

  • Park, TaeJo;Jang, InGyu
    • Tribology and Lubricants
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    • v.36 no.4
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    • pp.193-198
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    • 2020
  • Fluid film bearings are among the best devices used for overcoming friction and reducing wear. Surface texturing is a new surface treatment technique used for processing grooves and dimples on the lubricated surface, and it helps to minimize friction further and improve the wear resistance. In several studies, parallel surfaces, such as thrust bearings and mechanical face seals, have been investigated, but most sliding bearings have a convergent film shape. This paper presents the third part of a recent study and focuses on the effect of the groove shape on the lubrication performance of inclined slider bearings, following the two previous papers on the effects of the groove position and depth. We adopted the continuity and Navier - Stokes equations to conduct numerical analyses using FLUENT, which is a commercial computational fluid dynamics code. The groove shape adopted in the numerical analysis is rectangular and triangular, and its depth is varied. The results show that the streamlines, pressure distributions, and groove shape significantly influence the lubrication performance of the inclined slider bearing. For both shapes, the load-carrying capacity (LCC) is maximum near the groove depth, where vortices occur. In the shallow grooves, the LCC of the rectangular shape is higher, but in deeper grooves, that of the triangular shape is higher. The deeper the rectangular groove, the higher the decrease in the frictional force. The results of this study can be used as design data for various sliding bearings.

A Study on Fire Resistance Character of a Tunnel and an Underground Structure (터널 및 지하구조물의 내화특성에 관한 연구)

  • Yoo, Sang-Gun;Kim, Jung-Joo;Park, Min-Yong;Kim, Eun-Kyum;Lee, Jun-Suk
    • Journal of the Korean Society for Railway
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    • v.13 no.2
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    • pp.194-200
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    • 2010
  • Recently, a longitudinal tunnel construction has increased because of subway construction extension, geomorphological effect and the development of construction Technologies etc. When the fire occurs in a tunnel and an underground structure, the many damage of human life and the economic losses are caused. In Korea, fire resistance character study of a tunnel and an underground structure is proceeding. However, when a concrete is exposed to high temperature, study of load carrying capacity reduction and stability evaluation for spalling of a concrete is not enough. Therefore in this study, fire resistance character of a concrete evaluated according to time heating temperature curve(RABT and RWS) and a result compared on virtual fire accident in order to apply fire scenario. Also this study performed thermo-mechanical coupled analysis of a FEM-based numerical technique and estimated fire-induced damage of a tunnel and an underground structure.

Confined Effect of Concrete Compressive Members Strengthened with Carbon Fiber Laminate (탄소섬유판으로 횡보강된 콘크리트 압축부재의 보강성능)

  • Chung, Lan;Lee, Hee-Kyoung;Kim, Sung-Chul;Yoo, Seong-Hoon;Kim, Joong-Koo
    • Magazine of the Korea Concrete Institute
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    • v.10 no.6
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    • pp.345-352
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    • 1998
  • Compressive strength of concrete compression members strengthend with carbon fiber laminate(CFL) were studied from the test results. Test parameters are spacing, thickness, width, ply and spliced length of carbon fiber laminates. Specimens strength with sheets failed with sudden tensile rupture of the laminate, which indicate very brittle failure mode. Test result shows that closer spacing and to increas thickness of CFL is more effective. But strengthening ratio with 1-ply CFL is more effective than that of specimen with 2-ply CFL. Compressive strength capacity of specimen splied 24cm shows almost similar strength to that of non-spliced specimen. The ultimate load carrying of specimen strengthened with CFL ranges 1.11~1.86 times of that of non-strengthened specimen.

Structural Behavior of Flexurally Reinforced FRP-Concrete Composite Compression Member with FRP (FRP로 휨보강된 FRP-콘크리트 합성압축재의 구조적 거동)

  • Park, Joon-Seok;Joo, Hyung-Joong;Nam, Jeong-Hun;Yoon, Soon-Jong
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.1 no.3
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    • pp.10-16
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    • 2010
  • In construction industries, new construction materials are needed to overcome some problems associated with the use of conventional construction materials due to the change of environmental and social requirements. Accordingly, the requirements to be satisfied in the design of civil engineering structures are diversified. As a new construction material in the civil engineering industries, fiber reinforced polymeric plastic (FRP) has a superior corrosion resistance, high specific strength/stiffness, etc. Therefore, such properties can be used to mitigate the problems associated with the use of conventional construction materials. Nowadays, new types of bridge piers and marine piles are being studied for new construction. They are usually made of concrete filled fiber reinforced polymeric plastic tubes (CFFT). In this paper, a new type of FRP-concrete composite pile which is composed of reinforced concrete filled FRP tube (RCFFT) is proposed to improve compressive strength as well as flexural strength. The load carrying capacity of proposed RCFFT compression member is discussed based on the result of experimental and analytical investigations.

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Estimation of Local Stress Change of Wall-Thinned Pipes due to Fluid Flow (유체유동에 의한 감육배관의 국부응력변화 평가)

  • Kim Young-Jin;Song Ki-Hun;Lee Sang-Min;Chang Yoon-Suk;Choi Jae-Boong
    • Journal of the Korean Institute of Gas
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    • v.10 no.3 s.32
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    • pp.7-12
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    • 2006
  • In this paper, a new evaluation scheme is suggested to estimate load-carrying capacities of wall thinned pipes. At first, computational fluid dynamics analyses employing steady-state and incompressible flow are carried out to determine pressure distributions in accordance with conveying fluid. Then, the variational pressures are applied as input condition of structural finite element analyses to calculate local stresses at the deepest point. The efficiency of proposed scheme was proven from comparison to conventional analyses results and it is recommended to consider the fluid structure interaction effect for exact integrity evaluation.

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A Study of Interference-Free Home PLC based on the Binary ZCD Code (연속직교 상관특성을 갖는 아진 코드 기반의 구내용 PLC에 관한 연구)

  • Cha, Jae-Sang;Kim, Seong-Kweon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.2
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    • pp.38-44
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    • 2006
  • In this paper, a new interference-free Home CDMA-PLC(Code Division Multiple Access-Power Line Communication) system based on the binary ZCD(Zero Correlation Duration) spreading code is proposed as a key solution to overcome the previous problems. Binary ZCD spreading code sets with enlarged family sizes are generated by carrying out a chip-shift operation of the preferred pairs. The properties or the proposed ZCD-PLC systems are effective for MPI(Multi-Path Interference) and MAI (Multiple Access Interference) cancellation in the CDMA-PLC systems. By BER performance simulation, we certified the availability of proposed ZCD-CDMA-PLC system.

Simulation of PZT monitoring of reinforced concrete beams retrofitted with CFRP

  • Providakis, C.P.;Triantafillou, T.C.;Karabalis, D.;Papanicolaou, A.;Stefanaki, K.;Tsantilis, A.;Tzoura, E.
    • Smart Structures and Systems
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    • v.14 no.5
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    • pp.811-830
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    • 2014
  • A numerical study has been carried out to simulate an innovative monitoring procedure to detect and localize damage in reinforced concrete beams retrofitted with carbon fiber reinforced polymer (CFRP) unidirectional laminates. The main novelty of the present simulation is its ability to conduct the electromechanical admittance monitoring technique by considerably compressing the amount of data required for damage detection and localization. A FEM simulation of electromechanical admittance-based sensing technique was employed by applying lead zirconate titanate (PZT) transducers to acquire impedance spectrum signatures. Response surface methodology (RSM) is finally adopted as a tool for solving inverse problems to estimate the location and size of damaged areas from the relationship between damage and electromechanical admittance changes computed at PZT transducer surfaces. This statistical metamodel technique allows polynomial models to be produced without requiring complicated modeling or numerous data sets after the generation of damage, leading to considerably lower cost of creating diagnostic database. Finally, a numerical example is carried out regarding a steel-reinforced concrete (RC) beam model monotonically loaded up to its failure which is also retrofitted by a CFRP laminate to verify the validity of the present metamodeling monitoring technique. The load-carrying capacity of concrete is predicted in the present paper by utilizing an Ottosen-type failure surface in order to better take into account the passive confinement behavior of retrofitted concrete material under the application of FRP laminate.

Experimental compressive behavior of novel composite wall with different width-to-thickness ratios

  • Qin, Ying;Chen, Xin;Zhu, Xing-Yu;Xi, Wang;Chen, Yuan-Ze
    • Steel and Composite Structures
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    • v.36 no.2
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    • pp.187-196
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    • 2020
  • Double skin composite wall system owns several structural merits in terms of high load-carrying capacity, large axial stiffness, and favorable ductility. A recently proposed form of truss connector was used to bond the steel plates to the concrete core to achieve good composite action. The structural behavior of rectangular high walls under compression and T-shaped high walls under eccentric compression has been investigated by the authors. Furthermore, the influences of the truss spacings, the wall width, and the faceplate thickness have been previously studied by the authors on short walls under uniform compression. This paper experimentally investigated the effect of width-to-thickness ratio on the compressive behavior of short walls. Compressive tests were conducted on three short specimens with different width-to-thickness ratios. Based on the test results, it is found that the composite wall shows high compressive resistance and good ductility. The walls fail by local buckling of steel plates and crushing of concrete core. It is also observed that width-to-thickness ratio has great influence on the compressive resistance, initial stiffness, and strain distribution across the section. Finally, the test results are compared with the predictions by modern codes.

Elasto-plastic time history analysis of an asymmetrical twin-tower rigid-connected structure

  • Wu, Xiaohan;Sun, Yanfei;Rui, Mingzhuo;Yan, Min;Li, Lishu;Liu, Dongze
    • Computers and Concrete
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    • v.12 no.2
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    • pp.211-228
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    • 2013
  • The structure analyzed in this paper has particular building style and special structural system. It is a rigid-connected twin-tower skyscraper with asymmetrical distribution of stiffness and masses in two towers. Because of the different stiffness between the north and the south towers, the torsion seismic vibration is significant. In this paper, in order to study the seismic response of the structure under both frequent low-intensity earthquakes as well as rare earthquakes at the levels of intensity 7, the analysis model is built and analyzed with NosaCAD. NosaCAD is an nonlinear structure analysis software based on second-development of AutoCAD with ObjectARX. It has convenient modeling function, high computational efficiency and diversity post-processing functions. The deformations, forces and damages of the structure are investigated based on the analysis. According to the analysis, there is no damage on the structure under frequent earthquakes, and the structure has sufficient capacity and ductility to resist rare earthquakes. Therefore the structure can reach the goal of no damage under frequent earthquakes and no collapse under rare earthquakes. The deformation of the structure is below the limit in Chinese code. The time sequence and distribution of damages on tubes are reasonable, which can dissipate some dynamic energy. At last, according to forces, load-carrying capacity and damage of elements, there are some suggestions on increasing the reinforcement in the core tube at base and in stiffened stories.