• Title/Summary/Keyword: axial forces

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Seismic Performance Evaluation of Reinforced Concrete Columns Under Constant and Varying Axial Forces (일정 및 변동 축력을 받는 철근콘크리트 기둥의 내진성능 평가)

  • Lee, Do Hyung
    • Journal of the Earthquake Engineering Society of Korea
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    • v.28 no.1
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    • pp.59-65
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    • 2024
  • This paper describes the seismic performance evaluation of reinforced concrete bridge columns under constant and varying axial forces. For this purpose, nine identical circular reinforced concrete columns were designed seismically by KIBSE (2021) and KCI (2021). A comparison of lateral forces with theoretical strength shows that the safety factor for columns under varying axial forces is less marginal than those under constant axial forces. In addition, columns under varying axial forces exhibit significant fluctuations in the hysteretic response due to continuously varying axial forces. This is particularly prominent when many varying axial force cycles within a specific lateral loading cycle increase. Moreover, the displacement ductility of columns under varying axial forces does not meet the code-specified required ductility in the range of varying axial forces. All varying axial forces affect columns' strength, stiffness, and displacement ductility. Therefore, axial force variation needs to be considered in the lateral strength evaluation of reinforced concrete bridge columns.

Studies on Coupled Vibrations of Diesel Engine Propulsion Shafting (2nd Report : Analyzing of Forced Vibration with Damping) (디젤기관 추진축계의 연성진동에 관한 연구 (제2보: 강제 감쇠 연성진동 해석))

  • 이돈출;김의간;전효중
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2000.11a
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    • pp.99-107
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    • 2000
  • With the results of calculation for natural frequencies, the forced reponses of coupled vibration of propulsion shafting were analysed by the modal analysis method. For the forced response analysis, axial exciting forces, axial damper/detuner, propeller exciting forces and damping coefficients were extensively investigated. As the conclusion of this study, some items are cleared as next. - The torsional amplitudes are not influenced by the radial excitation forces. - The axial vibrational amplitudes are influenced by the tangential exciting forces. An increase of amplitude is observed for the speed range in the neighbourhood of any torsional critical speed. - The coupling effect becomes larger if torsional and axial critical speed are closer together. - The axial exciting force of propeller is relatively strong, comparing with those of axial forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, as a resume one can say, that- Torsional vibration calculation with the classical one dimension model is still valid. - The influence of torsional excitation at each crank upon the axial vibration is impotent, especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimension model is insufficient in most of cases. - The torsional exciting torque of propeller can be neglected in most of cases. But, the axial exciting forces of propeller can not be neglected for calculating axial vibration of propulsion shafting.

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Test and Evaluation of the CWR on Steel Plate Girder Railway Bridge (판형교 장대레일 부설에 따른 계측 및 평가)

  • Min Kyung-Joo;Shim Hyun-Woo;An Yong-Deuk
    • Proceedings of the KSR Conference
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    • 2005.05a
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    • pp.568-573
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    • 2005
  • To the installed CWR (Continuously Welded Rail) on steel plate girder bridges without ballast, shoes were replaced by the shoe for reduced axial force. During 9 months, from summer to winter, expansion by a temperature on girders, axial forces by a temperature on CWR, etc. are tested and the results are evaluated. Also, with the numerical analysis, the results - axial forces by a temperature on CWR, deformations of girders, etc. are compared and evaluated. From the longitudinal displacement on girders, occurred by run of trains, because of looking for the stability, the bearings for reducing axial forces are applied to the railway bridges. It is verified that the bearings for reducing axial forces disperse the axial forces by a temperature from the measurement of the forces on CWR of plate girder bridges,.

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Studies on Coupled Vibrations of Diesel Engine Propulsion Shafting(2nd Report: Analyzing of Forced Vibration with Damping) (디젤기관 추진축계의 연성진공에 관한 연구(제2보 : 강제 감쇠 연성진동해석))

  • 전효중;이돈출;김의간;김정렬
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.3
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    • pp.563-572
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    • 2001
  • With the results of calculation for natural frequencies the reponses of forced coupled vibration of propulsion shafting system were investigated by the modal analysis method. For the forced vibration response analysis, the axial exciting forces, the axial damper/detuner, propeller exciting forces and damping coefficients were extensively considered. As the conclusion of this study, some items are cleared as follows.-The torsional vibration amplitudes are not influenced by the radial excitation forces of the crank shaft. -The axial vibration amplitudes are influenced by the tangential exciting forces as well as the radial exciting forces of the crank shaft. The increase of the amplitudes is observed in the speed range at the neighbourhood of any torsional critical speed. 1The closer the torsional and axial critical speed. the larger coupling effect becomes. -The axial exciting force of propeller is relatively strong comparing with axial exciting forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, the following conclusions are obtained. -Torsional vibration calculation with the classical one dimensional model is still valid. -The influence of torsional excitation at each crank upon the axial vibration is improtant. especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimensional model is inaccurate in most of cases.

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Performance Improvement on Plate Girder Bridges Through Continuous Welded Rail (판형교 장대화에 따른 성능 개선)

  • Min, Kyung-Joo;Bahn, Gul-Yong;Ryu, Yeon-Jong
    • Proceedings of the KSR Conference
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    • 2007.05a
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    • pp.1439-1449
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    • 2007
  • The challenging aspect of CWR (continuous welded rail) is the additional axial forces in rails, mainly due to the thermal expansion of steel plate girder and rail itself. It has been found that these axial forces are proportional to girder length, total bridge length and bolt tightening forces. Also these forces are dependent to girder support conditions, types of bearings and their arrangements. With CWR, the authors' previous studies show that performance improvements like noise reduce, fatigue resistances and bearing durability increment can be expected. In addition to these effects, secondary effects due to the semi integral behavior between rail and bridge girder also can be expected. Special bearings which can reduce the absolute maximum axial forces have been developed, and applied to real 100m span bridge. The performance improvements were verified through site measurements and numerical analysis. The purpose of this study is to confirm the expected performance improvement aspects of steel plate girder bridges with CWR. To verify these aspects, girder stiffness changes, rail axial force changes, girder displacements and noise level were thoroughly measured and compared.

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Behaviour of flush end-plate beam-to-column joints under bending and axial force

  • da Silva, Luis Simoes;de Lima, Luciano R.O.;da S. Vellasco, Pedro C.G.;de Andrade, Sebastiao A.L.
    • Steel and Composite Structures
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    • v.4 no.2
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    • pp.77-94
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    • 2004
  • Steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current specifications for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 10% of the beam's plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present paper is to describe some experimental and numerical work carried out at the University of Coimbra to try to extend the philosophy of the component method to deal with the combined action bending moment and axial force.

Integrated Driver for the Full Rotation Using Six-axial Forces by the Induction Type of Axial-gap Motor (유도형 축방향 모터의 6축력 제어를 이용한 대회전 구현용 통합 구동기)

  • Jung Kwang-Suk;Lee Sang-Heon
    • Journal of Institute of Control, Robotics and Systems
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    • v.12 no.8
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    • pp.798-804
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    • 2006
  • To overcome the limited relative uncertainty and work range of the existing planar stage and the bulk structure of the contact-less motor for rotation, the novel operating principle to realize the precise rotation is suggested. It uses the two-axial vector forces, normal force and thrust force, of three-induction type of axial motors located $120^{\circ}$ apart, resulting in the contact-free rotation of the mover. Firstly in this paper, the magnetic forces across the air gap are modeled and simulated under the various conditions. It clarifies the feasible range of the derived solution. And the algorithm compensating the strong cross couple between the forces and the control inputs; generally AC magnitude and slip frequency, is given to realize the independent control of six axes. Finally, for the successfully implemented system, the round test and the micro step test results are given.

Influence of the axial force on the behavior of endplate moment connections

  • Ghassemieh, Mehdi;Shamim, Iman;Gholampour, Ali Akbar
    • Structural Engineering and Mechanics
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    • v.49 no.1
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    • pp.23-40
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    • 2014
  • In this article, using finite element method of analysis (FEM), behavior of the endplate moment connection subjected to axial force and bending moment is investigated. In the FEM model, all the nonlinear characteristics such as material, geometry, as well as contact have been included. First, in order to verify the numerical model of the connection, an analysis of the endplate moment connection conducted without the application of the axial force. Results obtained from FEM indicating a close and good correlation with the experimental results. Then to investigate the influence of the axial forces, the connections subjected to axial forces as well as the bending moment are analyzed. To observe the overall effect of these actions, the momentaxial force interaction diagrams are drawn. It is observed that the presence of axial force even in a small value can change the behavior of the connection significantly. It is also shown that the axial forces can alter the failure mode of the connection; and therefore it could result in a different than the predicted moment capacity of the connection.

Study on the measurement of bolt axial force by ultrasonic wave (초음파에 의한 볼트의 축력측정)

  • 한응교;김재열
    • Journal of the korean Society of Automotive Engineers
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    • v.10 no.3
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    • pp.38-44
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    • 1988
  • It is important to control the axial forces of high tension bolts such as the automobile, construction machine, aircraft, marine engine bolts. However, the direct method to measure the axial forces of bolts practically have not been found out. The ultrasonic techniques is based on the principles that the bolt tensile elongation and ultrasonic velocity changes are proportional to the axial force below the yield point of the materials. From the result of the experiment, the coefficient of acoustoelasticity k could be measured as - 11.18*10$_{-5}$m $m^{2}$k $g_{f}$./.

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Experimental axial force identification based on modified Timoshenko beam theory

  • Li, Dong-sheng;Yuan, Yong-qiang;Li, Kun-peng;Li, Hong-nan
    • Structural Monitoring and Maintenance
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    • v.4 no.2
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    • pp.153-173
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    • 2017
  • An improved method is presented to estimate the axial force of a bar member with vibrational measurements based on modified Timoshenko beam theory. Bending stiffness effects, rotational inertia, shear deformation, rotational inertia caused by shear deformation are all taken into account. Axial forces are estimated with certain natural frequency and corresponding mode shape, which are acquired from dynamic tests with five accelerometers. In the paper, modified Timoshenko beam theory is first presented with the inclusion of axial force and rotational inertia effects. Consistent mass and stiffness matrices for the modified Timoshenko beam theory are derived and then used in finite element simulations to investigate force identification accuracy under different boundary conditions and the influence of critical axial force ratio. The deformation coefficient which accounts for rotational inertia effects of the shearing deformation is discussed, and the relationship between the changing wave speed and the frequency is comprehensively examined to improve accuracy of the deformation coefficient. Finally, dynamic tests are conducted in our laboratory to identify progressive axial forces of a steel plate and a truss structure respectively. And the axial forces identified by the proposed method are in good agreement with the forces measured by FBG sensors and strain gauges. A significant advantage of this axial force identification method is that no assumption on boundary conditions is needed and excellent force identification accuracy can be achieved.