• Computational Structural Engineering
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• v.9 no.1
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• pp.33-45
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• 1996

A general stiffener element which includes transverse shear deformation is formulated using the p-version finite element method. Hierarchic C/sup o/-shape functions, derived from Integrals of Legendre polynomials, are used to define the assembled stiffness matrix of the stiffener with respect to the local reference frame is transformed to the plate reference system by applying the appropriate transformation matrices in order to insure compatibility of displacements at the junction of the stiffener and plate. The transformation matrices which account for the orientation and the eccentricity effects of the stiffener with respect to the plate reference axes are used to find local behavior at the junction of the stiffener and the relative contributions of the plate and stiffener to the strength of the composite system. The results obtained by the p-version finite element method are comared with the results in literatures, especially those by the h-version finite element analysis program, MICROFEAP-II.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.237-244
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• 2020

This study investigates the effect of the outrigger wall reinforced with post-tension on reducing differential column shortening. Since the outrigger wall is a concrete structure, the effect of its long-term behavior should be considered. The long-term behavior of the outrigger wall increases differential column shortening and decreases the shear force acting on the outrigger. When the stiffness of the outrigger becomes small, the effect of its long-term behavior increases. Furthermore, a method of reinforcing with post-tension to reduce differential column shortening is proposed. Following the analysis, it was confirmed that the post-tension method shows a significant reduction in the differential column shortening. This study shows that the effect of the outrigger wall reinforced with post-tension on reducing differential column shortening increases with the prestressing force of tendon.

• International Journal of Highway Engineering
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• v.7 no.4 s.26
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• pp.141-150
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• 2005

The behavior of the concrete slabs-on-grade considering the horizontal resistance at the slab bottom, which exists due to the shear resistance of the foundation and the friction between the slab and the foundation, has been investigated when the slabs-on-grade are subjected to the vertical load. Analytical formulations have been developed to include the effect of the horizontal resistance at the slab bottom, and the solutions have been obtained in the transformed field domain using the Fourier transform. Finite element formulations have also been developed using the plate bending elements and the flat shell elements. The solutions from the analytical and numerical models have been compared and showed very good agreement. The sensitivity of the horizontal resistance to the stresses of the concrete slab has been investigated with various values of the slab thickness, elastic modulus, and vertical stiffness of the foundation. The analysis results show that the horizontal resistance at the plate bottom can significantly affect the stresses of the slab.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.279-288
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• 2008

In this study, the slip behavior of high-tension bolted joints subjected to compression force is investigated through 3D finite element analysis and experiments. The relation with sliding load, bolt deformation, and failure load are studied with the metal thickness affecting the bolted joint. The post-sliding behavior considering bolt stiffness is presented and compared with the results by finite element and experiments. The finite element model is constructed by solid elements in ABAQUS, in consideration of all the friction effects between metal plates and bolts. The stress-strain relations in the literature are used, and the sliding displacements and axial stresses around the bolt connection are investigated. The flexural buckling of species happened when the plate thickness is less than the bolt diameter. However, the shear failures of bolt occurred in the opposite case.

• Journal of the Korean GEO-environmental Society
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• v.16 no.10
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• pp.5-14
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• 2015

Suction affects the unsaturated soil as the negative pore pressure, and leads to increases of the yield stress and the plastic shear stiffness of the soil skeleton due to the growth in interparticle stress. Hence, in this study, in order to account for these effects of suction under the dynamic loading condition such as the earthquake, the element simulation of the cyclic triaxial test using induced stress-strain relation based on cyclic elasto-plastic constitutive model extended for unsaturated soil considering the $1^{st}$ and the $2^{nd}$ yield functions was conducted. Through the stress path, stress-strain relation and relation between volumetric strain and axial strain, it was seen in all the cases that the simulation results demonstrated a good agreement with the experimental results. It is expected that the results of this study possibly contribute to the accuracy improvement on the prediction of unsaturated soil behavior under the dynamic loading condition.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.237-247
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• 1993

Carbon fiber reinforced plastics(CFRP) have gained increased application in aerospace structures because of their specific strength and stiffness, but are sensitive to impact-induced damage. An experimental investigation was carried out to evaluate the impact resistance of CFRP according to the ply angle. The specimens of angle ply laminate composites were employed with [0.deg. $_{6}$/ .deg.$_{10}$/0.deg.$_{6}$], in which 6 kinds of ply angle such as .deg.=15.deg., 30.deg., 45.deg., 60.deg., 75.deg. and 90.deg. were selected. The impact tests were conducted using the air gun type impact testing machine by steel balls of diameter of 5 mm and 10 mm, and impact-induced damages were evaluated under same impact speed of V=60m/s. The impact damaged zones were observed through a scanning acoustic microscope (SAM). The obtained results were summarized as follows: (1) Delaminations on the interfacial boundaries showed th directional characteristics to the fiber directions. The delamination area on the impact side (interface A) was considerably smaller compared to that of the opposite side (interface B). (2) Cracks corresponding to other delaminations than those mentioned in SAM photographs were also seen on the impact damaged zone. (3) The delamination patterns were affected by the ply-angle, the dimensions of the specimen, and the boundary conditions. (4) The impact damaged zone showed zone showed the delamination on the interfacial boundaries, transverse shear cracks of the surface layer, and bending cracks of the bottom layer.r.r.r.

• Fashion & Textile Research Journal
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• v.10 no.4
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• pp.566-571
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• 2008

Frictional sounds of 8 vapor permeable water repellent fabrics by sound generator were recorded and analyzed through FFT fast Fourier transform analysis. The frictional Sounds were quantified by calculating level pressure of total sound(LPT), the level range(${\Delta}L$) and the frequency difference(${\Delta}f$). Mechanical properties were measured by KES-FB. LPT values of specimens finished wet coating were higher than those of other kinds of finishing. ${\Delta}L$ values of specimens laminated were highest. Absolute values of ${\Delta}f$ were high in the cire finished and laminated specimens. Values for bending rigidity, shear stiffness and energy required for the compression of coated specimens increased compared with the cire finished and laminated specimens. Laminated specimens had high values of frictional coefficient and low values of surface roughness. Relationship between frictional sounds and mechanical properties analysed by use of correlation coefficients and stepwise regression. LPT showed significant correlation with elongation, tensile energy, geometrical roughness, weight and thickness. ${\Delta}L$ was highly correlated with tensile linearity, frictional coefficient, and ${\Delta}f$ with tensile linearity, weight and thickness. LPT were revealed to be explained by elongation and weight. ${\Delta}L$were predicted by tensile linearity, and ${\Delta}f$ by tensile linearity and thickness.

• Smart Structures and Systems
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• v.25 no.5
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• pp.515-530
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• 2020

A new type of pure torsional yielding damper made from steel pipe is proposed and introduced. The damper uses a special mechanism to apply force and therefore applies pure torsion in the damper. Uniform distribution of the shear stress caused by pure torsion resulting in widespread yielding along pipe and consequently dissipating a large amount of energy. The behavior of the damper is investigated analytically and the governing relations are derived. To examine the performance of the proposed damper, four types of the damper are experimentally tested. The results of the tests show the behavior of the system as stable and satisfactory. The behavior characteristics include initial stiffness, yielding load, yielding deformation, and dissipated energy in a cycle of hysteretic behavior. The tests results were compared with the numerical analysis and the derived analytical relations outputs. The comparison shows an acceptable and precise approximation by the analytical outputs for estimation of the proposed damper behavior. Therefore, the relations may be applied to design the braced frame system equipped by the pure torsional yielding damper. An analytical model based on analytical relationships was developed and verified. This model can be used to simulate cyclic behavior of the proposed damper in the dynamic analysis of the structures equipped with the proposed damper. A numerical study was conducted on the performance of an assumed frame with/without proposed damper. Dynamic analysis of the assumed frames for seven earthquake records demonstrate that, equipping moment-resisting frames with the proposed dampers decreases the maximum story drift of these frames with an average reduction of about 50%.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.181-190
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• 2005

In the conventional outrigger system, the outriggers are located in the planes of the core walls and this system has disadvantage of obstructing flexibility in the interior layout. But thc facade riggers in the structure uc located In the exterior frames in the direction of the lateral loading. The interaction between the traced frames and facade riggers is through the floor diaphragms adjacent to the chords of the riggers. This paper presents an approximate analysis technique lot preliminary analysis of multiple facade rigger stiffened braced frames in tall buildings subjected to uniformly and triangularly distributed loads as well as a lateral point load at the top of the structure. Comparisons with the results by the program MIDAS for the structural models have shown that this analysis can give reasonably accurate results for highrise braced frames with multiple facade riggers. The method allows a simple procedure for obtaining the optimum level of the facade riggers in addition to a rapid assessment of the influence of the facade riggers on the performance of the highrise structure such as the reduction in lateral deflection at the top and the overturning moment at the base of the braced frame.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.21-27
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• 2001

In this paper, a nonlinear finite element procedure is presented for the dynamic analysis of reinforced concrete shells. A computer program, named RCAHEST(reinforced concrete analysis in higher evaluation system technology), for the analysis of reinforced concrete structures was used. A 4-node flat shell element will drilling rotational stiffness is used for spatial discretization. The layered approach is used to discretize behavior of concrete and reinforcement through the thickness. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. Solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor(HHT) algorithm. The proposed numerical method for the nonlinear dynamic analysis of reinforced concrete shells is verified by comparison with reliable analytical results.