• Journal of the Korean Society of Safety
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• v.13 no.2
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• pp.45-53
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• 1998

A method to predict the creep behavior of fiber-reinforced ceramic composites at high temperatures was suggested based on finite element modeling using constituent creep equations of fiber and matrix and showed good agreement with the experimental results. The effects of matrix creep behavior, fiber volume fraction, and residual stresses on the composite creep behavior were also investigated. The results showed that the primary behavior of composites was greatly affected by that of matrix but post-primary behavior was governed by fiber creep characteristics. The increase of fiber volume fraction from 15 vol% to 30 vol% caused the 50% and 40% decrease of steady-state creep rates and total creep strains at $1200^{\circ}C$, 180MPa, respectively. Feasible compressive residual stresses in the matrix caused by different thermal expansion coefficients between the fiber and the matrix could significantly reduce total creep strains of the composite. The creep deformation mechanism in the fiber-reinforced ceramic composites could be explained by the stress transfer and redistribution in the fiber and matrix due to different creep characteristics of its constituents.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.297-302
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• 2000

This paper presents the effect of diaphragm spacing ratio(depth to span) on behavior and capacity of composite steel-concrete structures of sandwich system. Numerical analysis has been performed variety diaphragm ratio, behavior and load condition. As a results of this study, in case of shear behavior and concentrated load, the capacity of structure such as yielding and ultimate load improve according to diaphragm ratio because of concrete confining effect by steel plate and stress redistribution by diaphragm. But in case of bending behavior or uniform load, it proved that diaphragm ratio don't influence on behavior and capacity of composite structures of sandwich system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.107-110
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• 2005

In this study we investigated the shear and forming behavior of chain stitched multi-axial warp knitted fabric preform, so called non-crimp fabric (NCF). The picture frame test was performed to characterize the shear behavior of NCF and also provide material properties for the numerical simulation of its deformation behavior. The forming behavior of NCF with chain stitch were investigated using hemispherical forming tools. The experimental results show that processing conditions such as blank holder force (BHF) and preform shape are crucial to determining the forming behavior of NCF. For instance, an asymmetric formed shape, which is due to the stitches introduced to NCF, turns into a symmetric one as BHF increases. Furthermore the in-plane and out-of buckling (wrinkle), the severance of which were quantified using image processing method, decreases significantly as BHF increases.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.629-634
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• 2000

Comparing with single structure constructed with reinforced concrete or steel, composite structures have a great advantage. However, in case of nuclear power structure, the application of a conventional single structure (reinforced concrete or steel structure) inflicts a heavy loss on a economical and constructive efficiency. But, the application of composite slab to nuclear power structure could compensate these deficiency. Therefore, in this study, the structural behavior of composite slab in nuclear power structure is observed to assure economical and constructive efficiency.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.9-12
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• 2000

This paper deals with the torsional buckling behavior of plain weave GFRP composite cylindrical shells having comparatively small length-to-diameter ratio. Boundary conditions corresponding to clamped ends and simply supported ends are considered. Torsional buckling loads and circumferential mode numbers according to the variation of shell length-to-radius ratio are conformed. To verify the availability of the theoretical results, comparison with the theoretical and experimental results are made.

• Steel and Composite Structures
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• v.20 no.3
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• pp.719-729
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• 2016

There are great needs of simple but reliable mechanical nonlinear behavior analysis and performance evaluation method for frames constructed by steel and concrete composite beams or columns when the structures subjected extreme loads, such as earthquake loads. This paper describes an approach of simplified macro-modelling for composite frames consisting of steel-concrete composite beams and CFST columns, and presents the performance evaluation procedure based on the pushover nonlinear analysis results. A four-story two-bay composite frame underground is selected as a study case. The establishment of the macro-model of the composite frame is guided by the characterization of nonlinear behaviors of composite structural members. Pushover analysis is conducted to obtain the lateral force versus top displacement curve of the overall structure. The identification method of damage degree of composite frames has been proposed. The damage evolution and development of this composite frame in case study has been analyzed. The failure mode of this composite frame is estimated as that the bottom CFST columns damage substantially resulting in the failure of the bottom story. Finally, the seismic performance of the composite frame with high strength steel is analyzed and compared with the frame with ordinary strength steel, and the result shows that the employment of high strength steel in the steel tube of CFST columns and steel beam of composite beams benefits the lateral resistance and elasticity resuming performance of composite frames.

• Steel and Composite Structures
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• v.14 no.5
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• pp.409-429
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• 2013

A composite box-girder with corrugated steel webs has been used in civil engineering practice as an alternative to the conventional pre-stressed concrete box-girder because of several advantages, such as high shear resistance without vertical stiffeners and an increase in the efficiency of pre-stressing due to the accordion effect. Many studies have been conducted on the shear buckling and flexural behavior of the composite box-girder with corrugated steel webs. However, the torsional behavior is not fully understood yet, and it needed to be investigated. Prior study of the torsion of the composite box-girder with corrugated steel webs has been developed by assuming that the concrete section is cracked prior to loading and doesn't have tensile resistance. This results in poor estimation of pre-cracking behaviors, such as initial stiffness. To overcome this disadvantage of the previous analytical model, an improved analytical model for torsion of the composite box-girder with corrugated steel webs was developed considering the concrete tension behavior in this study. Based on the proposed analytical model, a non-linear torsional analysis program for torsion of the composite box-girder with corrugated steel webs was developed and successfully verified by comparing with the results of the test. The proposed analytical model shows that the concrete tension behavior has significant effect on the initial torsional stiffness and cracking torsional moment. Finally, a simplified torsional moment-twist angle relationship of the composite box-girder with corrugated steel webs was proposed based on the proposed analytical model.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.158-165
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• 2019

The purpose of this study is to investigate analytically the flexural behavior of beam reinforced by an alkali-activated slag-based fiber-reinforced composite. The materials and mixture proportion were selected to manufacture an alkali-activated slag-based fiber-reinforced composite with high tensile strain capacity over 7% and compressive strength and tension tests were performed. The composite showed a compressive strength of 32.7MPa, a tensile strength of 8.43MPa, and a tensile strain capacity of 7.52%. In order to analyze the flexural behavior of beams reinforced by ultra-high-ductile composite, nonlinear sectional analysis was peformed for four types of beams. Analysis showed that the flexural strength of beam reinforced partially by ultra-high-ductile composite increased by 8.0%, and the flexural strength of beam reinforced fully by ultra-high-ductile composite increased by 24.7%. It was found that the main reason of low improvement in flexural strength is the low tensile strain at the bottom of beam. The tensile strain at bottom corresponding to the flexural strength was 1.38% which was 18.4% of tensile strain capacity of the composite.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.89-92
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• 2002

Traditionally unidirectional laminated composite which are characterized by high specific stiffness and strength were used for structural application. But theses composites are highly susceptible to impact damage because of lower transverse tensile strength. The main failure modes of laminated composite are fiber breakage, matrix cracking and delamination for low velocity impact. The modified failure criterions are implemented to predict these failure modes with finite element analysis. Failure behavior of the woven fabric laminated composite which is used in forehead part of subway to lighten weigh has been studied. The new failure criterions are in good agreement with experimental results and can predict the failure behavior of the woven fabric composite plate subjected to low velocity impact more accurately.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.480-485
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• 2004

The applications of composite materials have increased over the past few decades in a variety of structures that require high ratio of stiffness and strength to weight ratios. Recently the thick open section composite beams are used extensively as load carrying members and stiffeners of structural elements. However, most of studies on thick composite beams are limited only to closed section beams. In this study, an open cross-section thick-walled composite beam model which includes coupled stiffness, transverse shear, and warping effects is suggested and the deflections associated with the thick-walled composite beams and thin-walled composite beams are obtained and compared with the finite element analysis results.