• Coupled systems mechanics
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• 제8권2호
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• pp.185-197
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• 2019

Considering the increasing use of tubular profiles in civil construction, this paper highlights the study on the behavior of welded connections between square hollow section column and I-beam, with emphasis on the assessment of the joint stiffness. Firstly, a theoretical analysis of the welded joints has been done focusing on prescriptions of the technical literature for the types of geometries mentioned. Then, a numerical analysis of the proposed joints were performed by the finite element method (FEM) with the software ANSYS 16.0. In this study, two models were evaluated for different parameters, such as the thickness of the cross section of the column and the sizes of cross section of the beams. The first model describes a connection in which one beam is connected to the column in a unique bending plane, while the second model describes a connection of two beams to the column in two bending planes. From the numerical results, the bending moment-rotation ($M-{\varphi}$) curve was plotted in order to determine the resistant bending moment and classify each connection according to its rotational capacity. Furthermore, an equation was established with the aim of estimating the rotational stiffness of welded I beam-to-RHS column connections, which can be used during the structure design. The results show that most of the connections are semi-rigid, highlighting the importance of considering the stiffness of the connections in the structure design.

• Ocean Systems Engineering
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• 제5권4호
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• pp.301-318
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• 2015

The present investigations introduce the shell-finite element discretization for the dynamics of slender marine pipelines. A long catenary pipeline, corresponding to a particular Steel Catenary Riser (SCR), is investigated under long-standing cyclic loading. The long structure is divided into smaller tubular parts which are discretized with 8-node planar shell elements. The transient analysis of each part is carried out by the implicit time integration scheme, within a Finite Elements (FE) solver. The time varying external loads and boundary conditions on each part are the results of a prior solution of an integrated line-dynamics model. The celebrated FE approximation can produce a more detailed stress distribution along the structural surface than the simplistic "line-dynamics" approach.

• 소성∙가공
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• 제19권1호
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• pp.32-37
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• 2010

Hydroforming has attracted a great deal of attention in the manufacturing industries for vehicles and transportation systems. Hydroforming technology contributes to weight reduction, increased strength, improved quality and reduced tooling cost. Hydroformed automotive parts used as structure components in vehichle body frame often have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. For a given flange shape, a parting plane for the dies is established relative to which the various surfaces of the flange shape, in cross section, have no significant reverse curvature. In this study, hydroforming process for flange forming was proposed. FE analysis to form flanged circular shape and flanged rectangular shape was preformed with Dynaform 5.5. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as tool geometry and hydraulic pressure has been performed and optimized. The results show that flanged automotive parts can be successfully produced with tube hydroforming.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.21-24
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• 2005

Three dimensional circular braided Glass/Aramid hybrid fabric/epoxy resin composite was fabricated. FBG sensor was embedded along the braid yam in order to monitor the internal dimensional changes of the 3-D braid composite. The amount of cure and thermal shrinkage of epoxy resin was also determined using FBG sensor system. FBG sensors with different grating length were embedded and their response were compared. The thermo-optic coefficient of FBG sensor was measured by several preliminary experiments. The internal strain that measured by FBG sensor and electric strain gauge was compared during compressive test. The released residual strain of the fabricated tubular composite was estimated using cutting method. The internal strain of the composite was estimated using FBG sensor system, and the result was compared with the value from electric strain gauge. It was found that FBG sensor system is a very useful technique to investigate inside region of complicated structure.

• Journal of Welding and Joining
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• 제33권5호
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• pp.9-13
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• 2015

Nickel alloy, especially Alloy 625, is used widely in industrial applications such as aerospace, chemical, petrochemical and marine applications due to their good mechanical properties, excellent fabricability, weldability and good corrosion resistance. Especially, it is obviously applied in FPSO's moon pool structure and caisson tubular of CPF under seawater environment. Recently, UNS S32654 was developed to substitute alloy 625 because of high cost price. In this study, mechanical properties and corrossive properties of UNS S32654 are reviewed and proposed its applications.

• Wind and Structures
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• 제31권1호
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• pp.1-14
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• 2020

This paper presents a method of estimation of fatigue demands on connection bolts of tubular steel wind turbine towers. The presented method relies on numerical simulation of aerodynamic loads and structural behavior of bolted connections modeled using finite element method. Variability of wind parameters is represented by a set of values derived from their probability densities, which are adjusted based on field measurements. Numerically generated stress time-series show agreement with the measurements from strain gauges inside bolts, in terms of power spectra and the resulting damage. Position of each bolt has a determining effect on its fatigue damage. The proposed framework for fatigue life estimation represents the complexities in loading and local behavior of the structure. On the other hand, the developed procedure is computationally efficient since it requires a limited number of simulations for statistically representing the wind variations.

• 한국분말재료학회지
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• 제6권3호
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• pp.238-245
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• 1999

The preparation of $n-TiO_2$ powder by the Chemical Vapor Synthesis process (CVS) was studied using the liquid metal organic precursor (TTIP). The residence time and the collection methods were considered as main processing variables through the experiments. The CVS equipment consisted of a micropump and a flashvaporizer, a tube furnace and a tubular collection device. The synthesis was performed at $1000^{\circ}C$ with various sets of collection zone. The residence time and the total system pressure were controlled in the range of 3~20 ms and 10 mbar, respectively. Nitrogen adsorption, X-ray diffraction and electron microscopy were used to determine particle size, specific surface area and crystallographic structure. The grain size of the as-prepared $n-TiO_2$ powder was in the range of 2~8 nm for all synthesis parameters and the powder exhibited only little agglomeration. The relationship between particle characteristics and the processing variables is reviewed based on simple growth model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.604-607
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• 2003

Recently, hybrid concrete structures such as a concrete-filled steel tubular(CFT), a steel reinforced concrete(SRC) and a composite material are popular in structure applications. They also have merit of high strength, high ductility, and large energy absorption capacity. But the analysis of hybrid concrete structures is very difficult owing to the complex behavior of concrete under passive confinement. This paper has analyzed CFT, which receives passive confinement using Tri-Surface concrete model for three dimension finite element analysis. By the result of that, the proposed model was properly forecasted a concrete behavior that receives passive restraint as well as non-linear analysis of concrete which receive uniaxial stress and high active confinement of 400Mpa. If the model through the steady study is set up especially on the factor of concrete under passive confinement, the proposed concrete model will be surely useful for analysis of the hybrid concrete structures.

• 한국가구학회지
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• 제23권3호
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• pp.271-289
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• 2012

This study analyzes the Western rocking chair style of the middle of the 20th century (1945~1970), and investigates academically characteristics from formative and practical points of view. The purpose of this study is to provide basic information on the design and production of the modern Korean rocking chair. In the 20th century, the production of the Western rocking chair displayed principles of both functionalism and optimism. These rocking chairs are constructed of various industrial materials including reinforced plastics, moulded plywood, aluminium, and steel as well as wood. Furthermore, a rocking chair suitable to the human body is made by industrial growth and innovative fabrication techniques such as designer's plastic from military in the First and Second World Wars. In those days, there are many different types of rocker style - traditional, plastics, structural, moulded plywood & bending, metal tubular, and wire mesh. More specifically, through economic prosperity and plastic development, the rocking chair is able to have light and bright colors, which shows sensible formality of the modern and structure.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.205-228
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• 2015

The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic load-displacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.