• Title/Summary/Keyword: high-axial load

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Seismic response of complex 3D steel buildings with welded and post-tensioned connections

  • Reyes-Salazar, Alfredo;Ruiz, Sonia E.;Bojorquez, Eden;Bojorquez, Juan;Llanes-Tizoc, Mario D.
    • Earthquakes and Structures
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    • v.11 no.2
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    • pp.217-243
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    • 2016
  • The linear and nonlinear seismic responses of steel buildings with perimeter moment resisting frames and welded connections (WC) are estimated and compared with those of buildings with post-tensioned connections (PC). Two-dimensional (2D) and three-dimensional (3D) structural representations of the buildings as well as global and local response parameters are considered. The seismic responses and structural damage of steel buildings with PC may be significantly smaller than those of the buildings with typical WC. The reasons for this are that the PC buildings dissipate more hysteretic energy and attract smaller inertia forces. The response reduction is larger for global than for local response parameters. The reduction may significantly vary from one structural representation to another. One of the main reasons for this is that the energy dissipation characteristics are quite different for the 2D and 3D models. In addition, in the case of the 3D models, the contribution of each horizontal component to the axial load on an specific column may be in phase each other during some intervals of time, but for some others they may be out of phase. It is not possible to observe this effect on the 2D structural formulation. The implication of this is that 3D structural representation should be used while estimating the effect of the PC on the structural response. Thus, steel frames with post-tensioned bolted connections are a viable option in high seismicity areas due to the fact that brittle failure is prevented and also because of their reduced response and self-centering capacity.

Test Result on Embedded Steel Column-to-Foundation Connection for Modular Unit Structural System (유닛 모듈러 기둥 매입형 기초 접합부에 대한 실험 연구)

  • Lee, Sang Sup;Bae, Kyu Woong;Park, Keum Sung;Hong, Sung Yub
    • Journal of Korean Society of Steel Construction
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    • v.26 no.6
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    • pp.537-547
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    • 2014
  • A steel modular unit structural system has been used increasingly for mid and high-rise buildings, since the building can be easily constructed by assembling the pre-made modular unit structures. For this structural system, each modular unit structures have to be properly connected to the foundation to transfer the axial force and the bending moment that are generated from external load to the ground. In this study, a new type of the embedded steel column-to-foundation connection was proposed, and its flexural behavior was evaluated through a series of experimental study. Five full scale specimens for the proposed connections were constructed and tested. The effect of the main parameters that affect the flexural behavior of the proposed connection, such as embedment length and shape of end plate, were studied. From the results, it was found that the flexural stiffness of the proposed connection was higher than that of the semi-rigid connection for all test specimens, and 200 mm of embedment length was proper for the given test specimens in this study.

Review of Acute Traumatic Closed Mallet Finger Injuries in Adults

  • Botero, Santiago Salazar;Diaz, Juan Jose Hidalgo;Benaida, Anissa;Collon, Sylvie;Facca, Sybille;Liverneaux, Philippe Andre
    • Archives of Plastic Surgery
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    • v.43 no.2
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    • pp.134-144
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    • 2016
  • In adults, mallet finger is a traumatic zone I lesion of the extensor tendon with either tendon rupture or bony avulsion at the base of the distal phalanx. High-energy mechanisms of injury generally occur in young men, whereas lower energy mechanisms are observed in elderly women. The mechanism of injury is an axial load applied to a straight digit tip, which is then followed by passive extreme distal interphalangeal joint (DIPJ) hyperextension or hyperflexion. Mallet finger is diagnosed clinically, but an X-ray should always be performed. Tubiana's classification takes into account the size of the bony articular fragment and DIPJ subluxation. We propose to stage subluxated fractures as stage III if the subluxation is reducible with a splint and as stage IV if not. Left untreated, mallet finger becomes chronic and leads to a swan-neck deformity and DIPJ osteoarthritis. The goal of treatment is to restore active DIPJ extension. The results of a six- to eight-week conservative course of treatment with a DIPJ splint in slight hyperextension for tendon lesions or straight for bony avulsions depends on patient compliance. Surgical treatments vary in terms of the approach, the reduction technique, and the means of fixation. The risks involved are stiffness, septic arthritis, and osteoarthritis. Given the lack of consensus regarding indications for treatment, we propose to treat all cases of mallet finger with a dorsal glued splint except for stage IV mallet finger, which we treat with extra-articular pinning.

Nominal Strength and Concrete Stress Block for Strength Analysis of Flexure and Compression Member (휨.압축 부재 강도 해석을 위한 콘크리트 압축 응력블럭 및 공칭 강도)

  • Lim, Kang-Sup;Sin, Sung-Jin;Choi, Jin-Ho;Lee, Jae-Hoon
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.11a
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    • pp.993-996
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    • 2008
  • Compression stress block used to concrete structure design substitutes equivalent triangle, rectangle, trapezoid and parabola-rectangle stress block for actual concrete stress distribution. Its shape is different in design code of the major advanced countries. It reflects the material feature of each of country. Presently, compression stress block of korea concrete design code is equal to it of ACI code that doesn't reflect the material feature of the high strength concrete. So, many research conclusions showed that it is not reasonable. The study compares concrete stress blocks of the major advanced countries and does an experiment on concrete compression stress block to know the material feature of the concrete in korea. It obtains the operating load and the concrete strain in experiment and draw stress block parameters. It compares stress block parameters applied to design code with those by the experiment conclusion. In addition, It compares and analyses nominal axial force-moment diagram by the stress block of the major advanced countries.

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Analysis of the Strain Rate Effect in Electro-Magnetic Forming (전자기 성형에서의 변형률 속도 효과 해석)

  • 곽신웅;신효철;이종수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1043-1058
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    • 1990
  • The Strain rate effect in electro-magnetic forming, which is one of the high velocity forming methods, is studied by the finite element method in this paper. The forming process is simplified by neglecting the coupling between magnetic field and work-piece deformation, and the impulsive magnetic pressure is regarded as inner pressure load. A rate-dependent elasto-plastic material model, of which tangential modulus depends of effective strain rate, is proposed. The model is shown to well describe the transient increase of yield stresses, the decreases of the final displacement and yield stress, the decrease of the difference in the distribution of deformation along the axial direction, and the change of deformation mechanism due to strain rate effect. As a result, displacement, final deformed shape, radial velocity, deformation energy, and the changes of effective stress, effective strain and effective strain rate through plastic working are given. Based on the results, the effectiveness of this model and the strain rate effect of the deformation process of the work-piece are discussed.

A Study on the Mechanical Properties of Concrete Filled Steel Tube Column under Centric Axial Load (중심축력을 받는 콘크리트 충전강관 기둥의 역학적 거동 특성에 관한 연구)

  • 박정민;김화중
    • Magazine of the Korea Concrete Institute
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    • v.7 no.5
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    • pp.133-144
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    • 1995
  • This study investigated to the properties of structural behaviors through a series of experiment with the key parameter, such as diameter-to-thickness(D/t) ratio, selenderness ratio of steel t~ube and strength of concrete under loading condition simple confined concrete by steel tube as a fundmental study on adaptability with structural members in high-rise building. The obtained results are sumnarised as follow. (1) The fracture mode of confined concrete was presented digonal tension fracture in the direction of $45^{\circ}$ with compression failure at the end of specimen in stub column, but the fracture mode of long column was assumed an aspect of bending fracture transversely. (2) The deformation capacity and ductility effect was increased by confine steel tube for concrete. (3) 'The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint of concrete considered D / t ratio, selenderness ratio of steel tube anti strength of' concrete were proposed.

Influence of NCG Charging Mass on the Heat Transport Capacity of Variable Conductance Heat Pipe (불응축가스량이 가변전열 히트파이프의 열수송 특성에 미치는 영향)

  • Suh Jeong-Se;Park Young-Sik;Chung Kyung-Taek
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.4
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    • pp.320-327
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    • 2006
  • Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

Approximate Analysis of Shear Wall-Frame Structure For Seismic Design (전단벽-골조 시스템의 내진설계를 위한 근사해석법)

  • Yoo, Suk-Hyung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.99-106
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    • 2019
  • A wall-frame structure resists horizontal load by the interaction between the flexural mode of the shear wall and the shear mode of the frame, which implies that the frame deflects only by reverse bending of the columns and girders, and that the columns are axially rigid. However, as the height of frame increases the shear mode of frame changes to flexural mode, which is due to the extension and shortening of the columns. An approximate hand method for estimating horizontal deflection and member forces in high-rise shear wall-frame structures subjected to horizontal loading is presented. The method is developed from the continuous medium theory for coupled walls and expressed in non-dimensional structural parameters. It accounts for bending deformations in all individual members as well as axial deformations in the columns. The deformations calculated from the presented approximate method and matrix analysis by computer program are compared. The presented approximate method is more accurate for the taller structures.

Comparative Study on Various Ductile Fracture Models for Marine Structural Steel EH36

  • Park, Sung-Ju;Lee, Kangsu;Cerik, Burak Can;Choung, Joonmo
    • Journal of Ocean Engineering and Technology
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    • v.33 no.3
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    • pp.259-271
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    • 2019
  • It is important to obtain reasonable predictions of the extent of the damage during maritime accidents such as ship collisions and groundings. Many fracture models based on different mechanical backgrounds have been proposed and can be used to estimate the extent of damage involving ductile fracture. The goal of this study was to compare the damage extents provided by some selected fracture models. Instead of performing a new series of material constant calibration tests, the fracture test results for the ship building steel EH36 obtained by Park et al. (2019) were used which included specimens with different geometries such as central hole, pure shear, and notched tensile specimens. The test results were compared with seven ductile fracture surfaces: Johnson-Cook, Cockcroft-Latham-Oh, Bai-Wierzbicki, Modified Mohr-Coulomb, Lou-Huh, Maximum shear stress, and Hosford-Coulomb. The linear damage accumulation law was applied to consider the effect of the loading path on each fracture surface. The Swift-Voce combined constitutive model was used to accurately define the flow stress in a large strain region. The reliability of these simulations was verified by the good agreement between the axial tension force elongation relations captured from the tests and simulations without fracture assignment. The material constants corresponding to each fracture surface were calibrated using an optimization technique with the minimized object function of the residual sum of errors between the simulated and predicted stress triaxiality and load angle parameter values to fracture initiation. The reliabilities of the calibrated material constants of B-W, MMC, L-H, and HC were the best, whereas there was a high residual sum of errors in the case of the MMS, C-L-O, and J-C models. The most accurate fracture predictions for the fracture specimens were made by the B-W, MMC, L-H, and HC models.

Computational optimized finite element modelling of mechanical interaction of concrete with fiber reinforced polymer

  • Arani, Khosro Shahpoori;Zandi, Yousef;Pham, Binh Thai;Mu'azu, M.A.;Katebi, Javad;Mohammadhassani, Mohammad;Khalafi, Seyedamirhesam;Mohamad, Edy Tonnizam;Wakil, Karzan;Khorami, Majid
    • Computers and Concrete
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    • v.23 no.1
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    • pp.61-68
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    • 2019
  • This paper presents a computational rational model to predict the ultimate and optimized load capacity of reinforced concrete (RC) beams strengthened by a combination of longitudinal and transverse fiber reinforced polymer (FRP) composite plates/sheets (flexure and shear strengthening system). Several experimental and analytical studies on the confinement effect and failure mechanisms of fiber reinforced polymer (FRP) wrapped columns have been conducted over recent years. Although typical axial members are large-scale square/rectangular reinforced concrete (RC) columns in practice, the majority of such studies have concentrated on the behavior of small-scale circular concrete specimens. A high performance concrete, known as polymer concrete, made up of natural aggregates and an orthophthalic polyester binder, reinforced with non-metallic bars (glass reinforced polymer) has been studied. The material is described at micro and macro level, presenting the key physical and mechanical properties using different experimental techniques. Furthermore, a full description of non-metallic bars is presented to evaluate its structural expectancies, embedded in the polymer concrete matrix. In this paper, the mechanism of mechanical interaction of smooth and lugged FRP rods with concrete is presented. A general modeling and application of various elements are demonstrated. The contact parameters are defined and the procedures of calculation and evaluation of contact parameters are introduced. The method of calibration of the calculated parameters is presented. Finally, the numerical results are obtained for different bond parameters which show a good agreement with experimental results reported in literature.