• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.6
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• pp.156-164
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• 1999

The body structure of a bus is generally assembled by using various spot welded box sectional members. The shape of window pillar joint is ordinarily built up by T-type member. It has been shown that T-type member has problems like high stress concentrations, low fatigue strength and low structural rigidity. In this study, to solve these problems a new approach to optimize the design of the bus window pillar joint was tried by FEM analysis and experiments. To describe the shape of the gusset connecting the vertical and horizontal members of the T-type window pillar joint B-spline curve was adopted and this curve was optimized . It was found that the new model developed could effectively improve fatigue durability an structural rigidity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.1
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• pp.137-146
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• 1999

Analysis of R/C columns requires modeling of the plastic hinge region, as well as nonlinear material characteristics. This becomes a challenging task in view of the nonlinearity of both steel and concrete. Furthermore, formation and progression of plasticity in the hinge is a difficult phenomenan to simulate, especially under reversed cyclic loading and decaying strength conditions. This research provide one analytical model employed in column analysis, including the analysis procedure for establishing inelastic force-deformation relationships. The analytical results show good correlation with experimental data. The employed procedure with the adopted analytical models can be used to compute inelastic displacements of concrete columns with welded reinforcement grids. The inelastic deformability beyond the peak was similar to those indicated by columns with conventional ties. The superior performance of columns with welded grids may be attributed to the improved confinement characteristics of grids associated with increased rigidity of welded ties.

• Structural Engineering and Mechanics
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• v.29 no.3
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• pp.241-258
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• 2008

This paper presents a new identification approach to prestress force. Firstly, a bridge deck is modeled as a prestressed Timoshenko beam. The time domain responses of the beam under sinusoidal excitation are studied based on modal superposition. The prestress force is then identified in the time domain by a system identification approach incorporating with the regularization of the solution. The orthogonal polynomial function is used to improve the noise effect and obtain the derivatives of modal responses of the bridge. Good identification results are obtained from only the first few measured modal data under both sinusoidal and impulsive excitations. It is shown that the proposed method is insensitive to the magnitude of force to be identified and can be successfully applied to indirectly identify the prestress force as well as other physical parameters, such as the flexural rigidity and shearing rigidity of a beam even under noisy environment.

• Steel and Composite Structures
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• v.3 no.2
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• pp.123-140
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• 2003

The importance of the research on moment-resistant properties of unstiffened tubular joints and the research background are introduced. The performed experimental research on the bending rigidity and capacity of the joints is reported. The emphasis is put on the discussion of the flexural behavior of the joints including sets of geometrical parameters of the joints and several loading combinations. Procedures and results of loading tests on four full size joints in planar KK and X configuration are described in details at first. Mechanical models are proposed to analyze the joint specimens. Three-dimensional nonlinear FE models are established and verified with the experimental results. By comparing the experimental data with the results of the analysis, it is reported reasonable to carry out the structural analysis under the assumption that the joint is fully rigidly connected, and their bending capacities can assure the strength of the members connected under certain limitation. Furthermore, a parametric formula for inplane bengding rigidity of T and Y type tubular joints is proposed on the basis of FE calculation and regression analysis. Compared with test results, it is shown that the parametric formula developed in this paper has good applicability.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.141-154
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• 2018

In this study, the bend-buckling strength of the web in longitudinally stiffened plate girder was numerically investigated. The buckling strength of the reinforced web was evaluated through an eigenvalue analysis of the hypothetical model, in which the top and bottom junctions of the web to the flanges were assumed as simple support conditions. Major parameters in the analysis include asymmetrical cross-sectional property, aspect ratio of the web, stiffener locations, and bending rigidity of the stiffeners. The numerical results showed that current AASHTO LRFD specifications (2014) provides the buckling strength from considerably safe side to slightly unsafe side depending on the location of the stiffeners. A modified equation for buckling coefficients was proposed to solve the shortcomings. The bending rigidity requirements of longitudinal stiffeners stipulated in AASHTO were also investigated. It is desirable to increase the rigidity of the stiffeners when the aspect ratio is less than 1.0.

• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.87-97
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• 2003

The structural system that discreterized from continuous shells is frequently used to make a large space structures. As well these structures show the unstable phenomena when a load level over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. In our real situation, most structures have semi-rigid joint that has middle characteristic between pin and rigid joint. So the knowledge of semi-rigid joint is very important problem of stable large space structure. And the instability phenemena of framed space structures show a strong non-linearity and very sensitive behavior according to the joint rigidity For this reason In this study, we are investigating to unstable problem of framed structure with semi-rigidity and to grasp the nonlinear instability behavior that make the fundamental collapse mechanism of the large space frame structures with semi-rigid joint, by proposed the numerical analysis method. Using the incremental stiffness matrix in chapter 2, we study instability of space structures.

• Fashion & Textile Research Journal
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• v.21 no.5
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• pp.597-605
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• 2019

This paper examined the garment formability and appearance of perspiration absorption, fast dry, and breathable fabrics. The mechanical properties and seam pucker properties of these fabrics were measured and regression analysis was conducted between fabric structural parameters and their mechanical and seam pucker properties. The superior total appearance value (TAV) of fast dry knitted fabrics for sports-wear was achieved in fabrics with high extensibility and bending rigidity; consequently, it increased with increasing stitch density and tightness factor. The formability of the fast dry knitted fabric also improved with an increasing stitch density and tightness factor. The seam pucker was influenced by bending rigidity and a good seam pucker was exhibited in the fast dry knitted fabrics with low stitch density and tightness factor. However, the formability (F) of the breathable fabric improved by increasing extensibility and bending rigidity that decreased with an increasing cover factor and the thickness of the breathable fabric. In addition, seam pucker deteriorated with an increasing cover factor and the thickness of the breathable fabric, which was similar to the results of the formability predicted in fabric mechanical properties. A superior seam pucker was achieved in fabrics with high extensibility and low bending rigidity.

• Steel and Composite Structures
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• v.31 no.4
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• pp.329-340
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• 2019

An innovated type of the flat steel plate-lightweight aggregate concrete hollow composite slab was presented in this paper. This kind of the slab is composed of flat steel plate and the lightweight aggregate concrete slab, which were interfaced with a set of perfobond shear connectors (PBL shear connectors) with circular hollow structural sections (CHSS) and the shear stud connectors. Five specimens were tested under static monotonic loading. In the test, the influence of shear span/height ratios and arrangements of CHSS on bending capacity and flexural rigidity of the composite slabs were investigated. Based on the test results, the crack patterns, failure modes, the bending moment-curvature curves as well as the strains of the flat steel plate and the concrete were focused and analyzed. The test results showed that the flat steel plate was fully connected to the lightweight aggregate concrete slab and no obvious slippage was observed between the steel plate and the concrete, and the composite slabs performed well in terms of bending capacity, flexural rigidity and ductility. It was further shown that all of the specimens failed in bending failure mode regardless of the shear span/height ratios and the arrangement of CHSS. Moreover, the plane-section assumption was proved to be valid, and the calculated formulas for predicting the bending capacity and the flexural rigidity of the composite slabs were proposed on the basis of the experimental results.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.227-235
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• 2018

Cables are the main load-bearing members of prestressed structure and other tensegrity structures. Based on the static equilibrium principle, a new cable force identification method considering cable flexural rigidity is proposed. Its computational formula is derived and the strategy to solve its implicit formula is introduced as well. In order to improve the reliability and practicality of this method, the influence of the cable flexural rigidity on cable force identification accuracy is also investigated. Through cable force identification experiments, the relationships among certain parameters including jacking force, jacking displacement, initial cable force, and sectional area (flexural rigidity) are studied. The results show that the cable force calculated by the proposed method considering flexural rigidity is in good agreement with the finite element results and experimental results. The proposed method with high computational accuracy and resolution efficiency can avoid the influences of the boundary condition and the length of the cable on calculation accuracy and is proven to be conveniently applied to cable force identification in practice.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.30 no.1
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• pp.53-62
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• 2024

Molded pulp products has become more attractive than traditional materials such as expanded polystyrene foam (EPS) owing to low-priced recycled paper, environmental benefits such as biodegradability, and low production cost. In this study, various design factors regarding compression and cushioning characteristics of the molded pulp cushion with truncated pyramid-shaped structural units were analyzed using a test specimen with multiple structural units. The adopted structural factors were the geometric shape, wall thickness, and depth of the structural unit. The relative humidity was set at two levels. We derived the cushion curve model of the target molded pulp cushion using the stress-energy methodology. The coefficient of determination was approximately 0.8, which was lower than that for EPS (0.98). The cushioning performance of the molded pulp cushion was affected more by the structural factors of the structural unit than by the material characteristics. Repeated impacts, higher static stress, and drop height decreased the cushioning performance. Its compression behavior was investigated in four stages: elastic, first buckling, sub-buckling, and densification. It had greater rigidity during initial deformation stages; then, during plastic deformation, the rigidity was greatly reduced. The compression behavior was influenced by structural factors such as the geometric shape and depth of the structural unit and environmental conditions, rather than material properties. The biggest difference in the compression and cushioning characteristics of molded pulp cushion compared to EPS is that it is greatly affected by structural factors, and in addition, strength and resilience are expected to decrease due to humidity and repetitive loads, so future research is needed.