• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.183-186
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• 2003

Long shafts for power transmission should transmit torsional load with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability. However, thermal residual stresses due to the coefficient difference of thermal expansion of the composite and metal are developed so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this work, axial compressive preload was given to the shaft in order to change the residual stresses. Static and fatigue torsional tests were performed and correlated with stress analyses with respect to the preload and service temperature.

• Earthquakes and Structures
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• v.15 no.2
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• pp.215-225
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• 2018

To reach a better foundation treatment project, an optimized analysis of composite foundation was studied in the field of hydraulic engineering. Its unique characteristics in hydraulic engineering were concluded. And, the overall and detailed analysis of the composite foundation model established was carried out. The index parameters of the vertical reinforced rigid pile composite foundation were formulated. Further, considering the unique role of cushion in hydraulic engineering, its penetration and regularity were analyzed. Then, comparative and optimized analyses of cushion multistage physical dimensions and multistage material characteristics were established. The parameters of the piles distance were optimized and the multilevel scientific and reasonable parameters information was obtained. Based on the information of these parameters, the practical application was verified. It effectively supported the effective application of vertical reinforcement rigid pile composite foundation in hydraulic engineering. The service mechanism of composite foundation was fully analyzed.

• Steel and Composite Structures
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• v.7 no.2
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• pp.105-118
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• 2007

On September $11^{th}$ 2001, the twin towers of the World Trade Center in New York City were struck by two hijacked airplanes. Despite severe local damage induced by the impact, the towers were able to sustain 102 and 56 minutes of the subsequent multi-storey fires before collapsing. The purpose of this study is to contribute to the understanding of the in-fire performance of composite trusses by examining the behaviour of the longer-span type used in the towers. It makes no attempt to be a forensic study of the actual events. Using the finite element package Vulcan, the structural mechanics of typical long-span composite floor trusses are explained, under a variety of scenarios, as the fire temperatures rise. Different boundary conditions, degrees of protection and loading are all covered, the results being presented mainly in the form of graphs of deflection and internal force of members against time.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.107-110
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• 2004

In this paper, a new structural health monitoring technique for composite laminates through the use of embedded fiber Bragg grating (FBG) sensors is presented. The method traces the ply stress states of a laminate and compares them with failure criteria during the service time of structures. The ply stress state of every ply composing the composite laminate can be obtained using classical lamination theory by embedded FBG sensors in the laminate. Graphite/epoxy laminate specimens, embedded with three FBG sensors, were fabricated. Tension tests were performed to evaluate the ply stress states tracing technique. Experimental results show that laminates experience fracture when the ply stress states are over the boundaries of failure criteria. In this method, critical damage can be detected by the ply stress states which are close to the boundaries of the failure criteria.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.98-102
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• 2003

The use of composite materials for the carbody structures of tilting train has many advantages because of manufacturing variety, specific high-strength & stiffness characteristics, and long-life durability, but the strongest advantage is the possibility of lightweight product. In the leading countries, the composite materials are used for the material for drivers' cabs, interior/exterior equipments for railway train, and it is now developing the composite materials applied for the train carbody structure. In this paper, we conducted the evaluation of structural stability for the all aluminum carbody, all composite carbody and hybrid carbody structures of the Korean Tilting Train eXpress(TTX) with the service speed of 180km/h.

• Steel and Composite Structures
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• v.2 no.2
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• pp.85-98
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• 2002

The aim of the paper is to present some results about the influence of rheological phenomena on steel-concrete composite beams. Both the cases of slab with normal and high performance concrete for one and two-span beams are analysed. A new finite element model that allows taking into account creep, shrinkage and cracking in tensile zones for concrete, along with non-linear behaviour of connection, steel beam and reinforcement, has been used. The main parameters that affect the response of the composite beam under the service load are highlighted. The influence of shrinkage on the slip over the supports is analysed, together with the cracking along the beam. At last, by performing a collapse analysis after a long-term analysis, the influence of rheological phenomena on the ductility demand of connection and reinforcement is analysed.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.79-90
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• 2009

A study has been made about the effects of powder content, reaction temperature, reaction time, and stirring speed on the preparation of the stainless steel(STS) 304L powders plating with copper by an electroless plating method. The behavior of corrosion resistance of the sintered STS-Cu composite powders was also investigated by the salt spraying test The electroless plating technique was an effective method to manufactur the copper-uniform plating composite powders, the corrosion resistance of this sintered specimen was improved bysuppressing Cr precipitates on grain boundaries in the sintered compacts of composite powders.

• Composites Research
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• v.17 no.1
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• pp.18-28
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• 2004

In order to evaluate the strength of carbody structures of railway rolling stock made of laminated fiber-reinforced composite materials, total laminate approach was introduced. Structural analyses were conducted to check the basic design of hybrid composite carbody structures of the Korean Tilting Train eXpress(TTX) with the service speed of 180km/h. The mechanical tests were also conducted to obtain strengths of composite laminates. The results show that all stress components of composite carbody structures are inside of failure envelopes and total laminate approach is recommended to predict the failure of hybrid composite carbody structures at the stage of the basic design.

• Advanced Composite Materials
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• v.18 no.3
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• pp.233-249
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• 2009

Safe installation and operation of high-pressure composite cylinders for hydrogen storage are of primary concern. It is unavoidable for the cylinders to experience temperature variation and significant thermal input during service. The maximum failure pressure that the cylinder can sustain is affected due to the dependence of composite material properties on temperature and complexity of cylinder design. Most of the analysis reported for high-pressure composite cylinders is based on simplifying assumptions and does not account for complexities like thermo-mechanical behavior and temperature dependent material properties. In the present work, a comprehensive finite element simulation tool for the design of hydrogen storage cylinder system is developed. The structural response of the cylinder is analyzed using laminated shell theory accounting for transverse shear deformation and geometric nonlinearity. A composite failure model is used to evaluate the failure pressure under various thermo-mechanical loadings. A back-propagation neural network (NNk) model is developed to predict the maximum failure pressure using the analysis results. The failure pressures predicted from NNk model are compared with those from test cases. The developed NNk model is capable of predicting the failure pressure for any given loading condition.

• Steel and Composite Structures
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• v.39 no.4
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• pp.419-433
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• 2021

In composite structures, shear connectors are crucial components to resist the relative slip between the steel and concrete, and thereby to achieve the composite actions. In the service stage, composite structures are usually in elastic state, so the elastic stiffness of the shear connection is a quite important parameter in the structural analysis of composite structures. Nevertheless, the existing studies mainly focus on the load-slip relationship rather than the tangent stiffness at the initial elastic stage. Furthermore, when composite beams subjected to torque or local load, shear connections are affected by both tensile force and shear force. However, the stiffness of shear connections under combined effects appears not to have been discussed hitherto. This paper investigates the initial elastic stiffness of stud connections under combined effects of biaxial forces. The initial expression and the relevant parameters are obtained by establishing a simplified analytical model of the stud connection. Afterwards, parametric finite element analysis is performed to investigate the effects of the relevant factors, including the stud length, stud diameter, elastic modulus of concrete, elastic modulus of steel and volume ratio of reinforcement. The feasibility of the proposed modelling has been proved by comparing with sufficient experimental tests. Based on the analytical analysis and the extensive numerical simulations, design equations for predicting the initial elastic stiffness of stud connections are proposed. The comparison between the equations and the data of finite element models demonstrates that the equations are accurate enough to serve for engineering communities.