• Title/Summary/Keyword: concentrated axial force

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Behaviour insights on damage-control composite beam-to-beam connections with replaceable elements

  • Xiuzhang He;Michael C.H. Yam;Ke Ke;Xuhong Zhou;Huanyang Zhang;Zi Gu
    • Steel and Composite Structures
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    • v.46 no.6
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    • pp.773-791
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    • 2023
  • Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.

Machinability evaluation according to variation of tool shape in high speed machining (고속가공용 엔드밀공구의 형상변화에 의한 성능평가)

  • 강명창;김정석;이득우;김광호;하동근
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.10a
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    • pp.393-398
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    • 2001
  • The technique of high speed machining is widely studied in machining fields, because the high efficiency and accuracy in machining can be obtained in high speed machining. Unfortunately the development of tool for high speed machining in not close behind that of machine tool. In this study, several types flat endmill is prepared for obtaining data according to tool shape. Especially, we concentrated in helix angle, number of cutting edge, rake angle and relief angle. Machinability is measured by cutting force, tool life, tool wear, chip shape and surface roughness according to cutting length. 3-axis cutting forces are acquired from the invented tool dynamometer for high speed machining. Particularly, we found out that the axial cutting force waveform has a good relation with tool wear features. By above results, it is suggested the endmill tool with $45^{\circ}$ helix angle, 6 cutting edge, $-15^{\circ}$ rake angle and $12^{\circ}$ relief angle be suitable for high speed machining

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Dynamic characteristics of elastic beams subjected to traffic loads

  • Tang, Chia-Chih;Wang, Yang-Cheng
    • Structural Engineering and Mechanics
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    • v.13 no.2
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    • pp.211-230
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    • 2002
  • The objective of this study is to investigate the dynamic behavior of elastic beams subjected to moving loads. Although analytical methods are available, they have limitations with respect to complicated structures. The use of computer technology in recent years is an effective way to solve the problem; thus using the latest technology this study establishes a finite-element solution procedure to investigate dynamic behaviors of a typical elastic beam having a set of constant geometric properties and various span lengths. Both the dead load of the beam and traffic load are applied in which the traffic load is considered a concentrated moving force with various traveling passage speeds on the beam. Dynamic behaviors including deflection, shear, and bending moment due to moving loads are obtained by both analytical and finite element methods; for simple structures, they have an excellent agreement. The numerical results show that based on analytical methods the fundamental mode is good enough to estimate the dynamic deflection along the beam, but is not sufficient to simulate the total response of the shear force or the bending moment. The linear dynamic behavior of the elastic beams subjected to multiple exciting loads can easily be found by linear superposition, and the geometric nonlinear results caused by large deformation and axial force of the beam are always underestimated with only a few exceptions which are indicated. In order to make the results useful, they have been nondimensionalized and presented in graphical form.

Dynamic Response Analysis of Twisted High-Rise Structures according to the Core Location Change (코어 위치 변화에 따른 비틀림 초고층 구조물의 동적응답분석)

  • Chae, Young-Won;Kim, Hyun-Su;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.22 no.1
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    • pp.17-24
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    • 2022
  • Currently, the construction trend of high-rise structures is changing from a cube-shaped box to a free-form. In the case of free-form structures, it is difficult to predict the behavior of the structure because it induces torsional deformation due to inclined columns and the eccentricity of the structure by the horizontal load. For this reason, it is essential to review the stability by considering the design variables at the design stage. In this paper, the position of the weak vertical member was analyzed by analyzing the behavior of the structure according to the change in the core position of the twisted high-rise structures. In the case of the shear wall, the shear force was found to be high in the order of proximity to the center of gravity of each floor of the structure. In the case of the column, the component force was generated by the axial force of the outermost beam, so the bending moment was concentrated on the inner column with no inclination.

Stress analysis on the implant fixture with the angulated placement (경사진 임플란트 고정체의 응력 분석)

  • Kim, Chang-Hyeon;Kang, Jae-Suek;Boo, Soo-Bung;Oh, Snag-Ho;An, OK-Ju;Kang, Dong-Wan
    • Journal of Dental Rehabilitation and Applied Science
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    • v.20 no.2
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    • pp.71-81
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    • 2004
  • The purpose of this study was to compare the distributing pattern of stress on the finite element models of two units implant prosthesis with one angulated placement of two implant fixtures. The two unit implant crowns simulated to mandibular first and second molars were made. The two kinds of finite element models were designed according to angulation of fixture ($4.0mm{\times}11.5mm$) : Model 1($15^{\circ}$ buccally angulated placement of one fixture on second molar area), Model 2($15^{\circ}$ lingually angulated placement of one fixture on second molar area). Axial loads of 200N were applied to the center of central fossa and to distance of 2mm and 4mm apart from the center of central fossa. Von-Mises stresses were recorded and compared in the fixtures, and buccolingual section of implants. The results were as follows: 1. Under axial loading at the central fossa, the stress was distributed along the straight fixture except apical portion, while on buccally or lingually angulated placement, the highest stresses were concentrated in the neck portion on the opposite side of the angulated fixture. 2. With offset distance increasing, the stresses were concentrated greater in buccal neck of lingually angulated fixture than in lingual neck of buccally angulated fixture. From the above results, in designing of the occlusal scheme for implant prosthesis with the angulated fixture, occlusal contacts should be placed to distribute stress axially in maximum intercuspation and to avoid offset force during eccentric movements.

Polymer Based Slim Tactile Sensor: Optimal Design and New Fabrication Method (폴리머 기반 슬림형 촉각센서의 최적 설계 및 새로운 공정 방법)

  • Lee, Jeong-Il;Sato, Kazuo
    • Journal of Institute of Control, Robotics and Systems
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    • v.17 no.2
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    • pp.131-134
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    • 2011
  • In this study, we propose an optimal design and new fabrication method for a slim tactile sensor. Slim tactile sensor can detect 3-axial forces and has suitable flexibility for intelligent robot fingers. To amplify the contact signal, a unique table-shaped structure was attempted. A new layer-by-layer fabrication process for polymer micromachining that can make a 3D structure by using a sacrificial layer was proposed. A table-shaped epoxy sensing plate with four legs was built on top of a flexible polymer substrate. The plate can convert an applied force to a concentrated stress. Normal and shear forces can be detected by combining responses from metal strain gauges embedded in the polymer substrate. The optimal positions of the strain gauges are determined using the strain distribution obtained from finite element analysis.

Length of Plastic Hinge in RC Columns under Cyclic Loading (반복 하중을 받는 철근콘크리트 기둥의 소성힌지 길이)

  • Park, Jong-Wook;Choi, Im-Jun;Moon, Cho-Hwa;Lee, Jung-Yoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2009.05a
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    • pp.11-12
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    • 2009
  • The small height to depth ratio column dominated by shear after tension steel yielded and the energy dissipation capacity reduce remarkably due to the affection of axial force. This procedure incur in the plastic hinge region and not in all of the region at the same time but from somewhere where the energy was concentrated. This study was reported about the variation of length of the plastic hinge under cyclic loading of the RC columns through the test.

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A Study on the Characteristics of Two-Phase Flow by Driven Bubbles (기포운동에 따른 2상유동 특성에 관한 연구)

  • 서동표;오율권
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.15 no.4
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    • pp.268-273
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    • 2003
  • In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas is concentrated at the near nozzle, the flow parameters are high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (P.I..V) and a thermo-vision camera were used in the present study. The experimental results show that heat transfer from bubble surface to water is largely completed within z=10mm from the nozzle, and then the temperature of bubble surface reaches that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

A Study on the Characteristics of Two-Phase Flow by Driven Bubbles in a Liquid Bath

  • Oh, Yool-Kwon;Seo, Dong-Pyo
    • International Journal of Air-Conditioning and Refrigeration
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    • v.13 no.1
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    • pp.44-50
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    • 2005
  • In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas was concentrated at the near the nozzle, the flow parameters were high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (PIV) and a thermo-vision camera were used in the present study. The experimental results showed that heat transfer from bubble surface to water was largely completed within z = 10 mm from the nozzle, and then the temperature of bubble surface reached that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

Effect of shear deformation on the critical buckling of multi-step bars

  • Li, Q.S.
    • Structural Engineering and Mechanics
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    • v.15 no.1
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    • pp.71-81
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    • 2003
  • The governing differential equation for buckling of a one-step bar with the effect of shear deformation is established and its exact solution is obtained. Then, the exact solution is used to derive the eigenvalue equation of a multi-step bar. The new exact approach combining the transfer matrix method and the closed form solution of one step bar is presented. The proposed methods is convenient for solving the entire and partial buckling of one-step and multi-step bars with various end conditions, with or without shear deformation effect, subjected to concentrated axial loads. A numerical example is given explaining the proposed procedure and investigating the effect of shear deformation on the critical buckling force of a multi-step bar.