• Title/Summary/Keyword: transverse forces

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Transverse earthquake-induced forces in continuous bridges

  • Armouti, Nazzal S.
    • Structural Engineering and Mechanics
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    • v.14 no.6
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    • pp.733-738
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    • 2002
  • A simplified rational method is developed to evaluate transverse earthquake-induced forces in continuous bridges. This method models the bridge as a beam on elastic foundation, and assumes a sinusoidal curve for both vibration mode shape and deflected shape in the transverse direction. The principle of minimum total potential is used to calculate the displacements and the earthquake-induced forces in the transverse direction. This method is concise and easy to apply, and hence, offers an attractive alternative to a lengthy and time consuming three dimensional modeling of the bridge as given by AASHTO under its Single Mode Spectral Analysis Method.

The effect of internal axial forces of a cantilever beam with a lumped mass at its free end

  • Zhang, Jinfu
    • Coupled systems mechanics
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    • v.7 no.3
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    • pp.321-331
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    • 2018
  • When a cantilever beam with a lumped mass at its free end undergoes free transverse vibration, internal axial forces are produced in the beam. Such internal axial forces have an effect on free transverse vibration of the beam. This effect is studied in this paper. The equations of motion for the beam in terms of the generalized coordinates including the effect are derived. The method for determining free transverse vibration of the beam including the effect is presented. In numerical simulations, the results of free transverse vibration of the free end of the beam including and not including the effect are obtained. Based on comparison between the results obtained, the conclusions concerning the effect are given.

Aeroelastic Behaviour of Aerospace Structural Elements with Follower Force: A Review

  • Datta, P.K.;Biswas, S.
    • International Journal of Aeronautical and Space Sciences
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    • v.12 no.2
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    • pp.134-148
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    • 2011
  • In general, forces acting on aerospace structures can be divided into two categories-a) conservative forces and b) nonconservative forces. Aeroelastic effects occur due to highly flexible nature of the structure, coupled with the unsteady aerodynamic forces, causing unbounded static deflection (divergence) and dynamic oscillations (flutter). Flexible wing panels subjected to jet thrust and missile type of structures under end rocket thrust are nonconservative systems. Here the structural elements are subjected to follower kind of forces; as the end thrust follow the deformed shape of the flexible structure. When a structure is under a constant follower force whose direction changes according to the deformation of the structure, it may undergo static instability (divergence) where transverse natural frequencies merge into zero and dynamic instability (flutter), where two natural frequencies coincide with each other resulting in the amplitude of vibration growing without bound. However, when the follower forces are pulsating in nature, another kind of dynamic instability is also seen. If certain conditions are satisfied between the driving frequency and the transverse natural frequency, then dynamic instability called 'parametric resonance' occurs and the amplitude of transverse vibration increases without bound. The present review paper will discuss the aeroelastic behaviour of aerospace structures under nonconservative forces.

Unbalanced Magnetic Forces in Rotational Unsymmetrical Transverse Flux Machine

  • Baserrah, Salwa;Rixen, Keno;Orlik, Bernd
    • Journal of Electrical Engineering and Technology
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    • v.7 no.2
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    • pp.184-192
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    • 2012
  • The torque and unbalanced magnetic forces in permanent magnet machines are resultants of the tangential, axial and normal magnetic forces, respectively. Those are in general influenced by pole-teeth-winding configuration. A study of the torque and unbalanced magnetic forces of a small flux concentrating permanent magnet transverse flux machine (FCPM-TFM) in segmented compact structure is presented in this paper. By using FLUX3D software from Cedrat, Maxwell stress tensor has been solved. Finite element (FE-) magneto static study followed by transient analysis has been conducted to investigate the influence of unsymmetrical winding pattern, in respect to the rotor, on the performance of the FCPM-TFM. Calculating the magnetic field components in the air gap has required an introduction of a 2D grid in the middle of the air gap, whereby good estimations of the forces are obtained. In this machine, the axial magnetic forces reveal relatively higher amplitudes compared to the normal forces. Practical results of a prototype motor are demonstrated through the analysis.

The Assessment of Safe Navigation Regarding Hydrodynamic forces between Ships in Restricted Waterways

  • Lee, Chun-Ki;Lee, Sam-Goo
    • Journal of Mechanical Science and Technology
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    • v.20 no.11
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    • pp.2002-2009
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    • 2006
  • This paper is primarily focused on the safe navigation between overtaking and overtaken vessels in restricted waterways under the external forces, such as wind and current. The maneuvering simulation between two ships was conducted to find an appropriate safe speed and distance, which is required to avoid collision. From the viewpoint of marine safety, a greater transverse distance between two ships is more needed for the smaller vessel. Regardless of external forces, the smaller vessel will get a greater effect of hydrodynamic forces than the bigger one. In the case of close navigation between ships under the forces of wind and current, the vessel moving at a lower speed is potentially hazardous because the rudder force of the lower speed vessel is not sufficient for steady-state course-keeping, compared to that of the higher speed vessel.

The assessment of Safe Navigation Regarding Hydrodynamic forces between ships in Restricted Waterways

  • Lee, Chun-Ki;Yoon, Jeom-Dong
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.89-93
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    • 2006
  • This paper is primarily focused on the safe navigation between overtaking and overtaken vessels in restricted waterways under the external forces, such as wind and current. The maneuvering simulation between two ships was conducted to find an appropriate safe speed and distance, which is required to avoid collision. From the viewpoint of marine safety, a greater transverse distance between two ships is more needed for the smaller vessel. Regardless of external forces, the smaller vessel will get a greater effect of hydrodynamic forces than the bigger one. In the case of close navigation between ships under the forces of wind and current, the vessel moving at a lower speed is potentially hazardous because the rudder force of the lower speed vessel is not sufficient for steady-state course-keeping, compared to that of the higher speed vessel.

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Analysis of concrete shrinkage along truss bridge with steel-concrete composite deck

  • Siekierski, Wojciech
    • Steel and Composite Structures
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    • v.20 no.6
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    • pp.1237-1257
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    • 2016
  • The paper concerns analysis of effects of shrinkage of slab concrete in a steel-concrete composite deck of a through truss bridge span. Attention is paid to the shrinkage alongside the span, i.e., transverse to steel-concrete composite cross-beams. So far this aspect has not been given much attention in spite of the fact that it affects not only steel-concrete decks of bridges but also steel-concrete floors of steel frame building structures. For the problem analysis a two-dimensional model is created. An analytical method is presented in detail. A set of linear equations is built to compute axial forces in members of truss girder flange and transverse shear forces in steel-concrete composite beams. Finally a case study is shown: test loading of twin railway truss bridge spans is described, verified FEM model of the spans is presented and computational results of FEM and the analytical method are compared. Conclusions concerning applicability of the presented analytical method to practical design are drawn. The presented analytical method provides satisfactory accuracy of results in comparison with the verified FEM model.

Crabbing Test of a 3m Ferry Model (3m Ferry 모형선의 Crabbing 시험)

  • 신현경;이형락
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.1
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    • pp.40-46
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    • 2004
  • In this paper, one of the harbour manoeuvring tests is described. its goal is to investigate the so-called crabbing performance of ships. By crabbing is meant the ability of the vessel to move sideways with the use of her own manoeuvring devices like propellers, rudders, transverse thruster, etc. The crabbing model tests were carried out in the Ocean Engineering Wide Tank, University of Ulsan(UOU) to measure the transverse forces and yawing moments by the transverse thruster alone and the propeller-rudder arrangement in combination with the bow thruster. The comparison between UOU crabbing test results and data measured at one of foreign research institutes showed a little gap due to different rotating conditions of controllable pitch propellers.

Crabbing Test of a 3m Ferry Model (II) (3m Ferry 모형선의 Crabbing 시험(II))

  • SHIN HYUN KYOUNG;LEE HYUNG LAK
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2004.05a
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    • pp.290-297
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    • 2004
  • In this paper, one of the harbour maneuvering tests is described. Its goal is to investigate the so-called crabbing performance of ships. By crabbing is meant the ability of the vessel to move sideways with the use of her own maneuvering devices like propellers, rudders, transverse thruster, etc. the 3m ferry model is made by ocean engineering wide tank in the university of ulsan. when the model ship is leaving and going to the quay, Transverse forces and Yawing moments are measured, in the condition of zero longitudinal force and the design draught, by load cell attached to the longitudinal center of gravity on the ship. the purpose of the experiment is to verify the reliability of ocean wide tank in university of ulsan about crabbing test compared with results of foreign research institute.

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Decoupling Control of Levitation and Thrust Motion of The Transverse Flux Linear Induction Motor Using DC-biased Multi Phase Inputs (DC 편의된 다상 입력을 이용한 횡자속 선형 유도 전동기의 부상/추진 독립제어)

  • Jung, Kwang-Suk;Huh, Jin-Hyuk;Baek, Yoon-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.11
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    • pp.1733-1740
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    • 2004
  • In the transverse flux linear induction motor(TFLIM) with the general secondary composed of conductor and back-yoke, there exists a magnetized force into the normal direction or the air-gap direction of the thrust motion as well as the thrust force. Therefore, the various methodologies have been tried to use the normal force by the two independent control variables of the multi-phase input. But, as the force depends inevitably and strongly on the thrust force, it is essential to decouple both forces for two control index. In this paper, we suggest a novel approach capable of compensating the couple between both forces and the control index by using the DC-biased multi-phase input, and then realizing the independent control of TFLIM.