• Computational Structural Engineering
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• v.8 no.3
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• pp.51-57
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• 1995

A simplified stress analysis of perforated plates was carried out using homogenization technique. Homogenization technique, which introduced miroscale expansion in the standard finite element method, reconstructed the plate with regularly placed holes into a set of macroscale and microscale models. The microscale model helped compute homogenized material constants of the unit cell, which were used to compute macroscale displacements in the macroscale model. Also it was possible to compute the stress field of the plate using the microscale model. It was found that reasonable equivalent material constants were computed and that the required degrees of freedom was drastically reduced when homogenization technique was employed in the stress analyses. The microscale modeling in the homogenization technique provided a useful concept of pre- and post-processing in the stress analysis of perforated plates.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.54-62
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• 2014

Manhole cover, which is usually made of grey cast iron and consists of frame and cover, should have enough strength to support the heavy traffic load. The manhole cover made of cast iron has heavy weight to handle manually and is vulnerable to impact force with its brittle characteristics. Moreover, its production process of casting has been regulated in terms of environmental pollution. In this study, steel manhole cover is proposed to substitute the cast cover with a series of structural analyses to confirm its strength to support the test load for manhole cover. The cover of the proposed steel manhole cover is made of thin circular pate and stiffeners below the plate. Rectangular columns and hollow circular plate were selected for the shape of the stiffener. In order to give enough strength for the cover to behave within elastic range in the loading, strengthening structures of the cover were varied with increasing the number and the size of the stiffeners. The results of the analyses revealed that when both the hollow circular stiffener and cross stiffeners were additionally applied at the same time to the steel cover with longitudinal stiffeners, the maximum stress level in the cover could be reduced to that level presented in the cast cover.

• Journal of Welding and Joining
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• v.9 no.2
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• pp.44-50
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• 1991

The use of high tensile steel plates is increasing in the fabrication of ship and offshore structures. The softening region which has lower yield stress than base metal is located to prevent cracking in the conventional high tensile steel. Also, thermo mechanical control process(TMCP) steel with low carbon equivalent has the softening region which occurs in the heat affected zone when high heat input weld is carried out. The softening region in the high tensile steel gives rise to serious effect on structural strength such as tensile strength, fatigue strength and ultimate strength. In order to make a reliable structural design using high tensile steel plates, the influence of the softening on plate strength should be evaluated in advance. In the previous paper, the authors discussed the ultimate compressive strength of 50HT steel square plates with softening region. In this paper, the ultimate compressive strength with varying the yield stress of softening region and the aspect ratio of the plate is investigated by using the elasto-plastic large deformation finite element method.

• Steel and Composite Structures
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• v.19 no.5
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• pp.1203-1219
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• 2015

'Distortional buckling' is one of the predominant buckling types that may occur in a steel-concrete composite box beam (SCCBB) under a negative moment. The key factors, which affect the buckling modes, are the torsional and lateral restraints of the bottom plate of a SCCBB. Therefore, this article investigates the equivalent lateral and torsional restraint rigidity of the bottom plate of a SCCBB under a negative moment; the results of which show a linear coupling relationship between the applied forces and the lateral and/or torsional restraint stiffness, which are not depended on the cross-sectional properties of a SCCBB completely. The mathematical formulas for calculating the lateral and torsional restraint rigidity of the bottom plate can be used to estimate: (1) the critical distortional buckling stress of SCCBBs under a negative moment; and (2) the critical distortional moment of SCCBBs. This article develops an improved calculation method for SCCBBs on an elastic foundation, which takes into account the coupling effect between the applied forces and the lateral and/or torsional restraint rigidity of the bottom plate. This article analyzes the accuracy of the following calculation methods by using 24 examples of SCCBBs: (1) the conventional energy method; (2) the improved calculation method, as it has been derived in this article; and (3) the ANSYS finite element method. The results verify that the improved calculation method, as it has been proved in this article, is more accurate and reliable than that of the current energy method, which has been noted in the references.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.10
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• pp.5974-5979
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• 2014

Lightweight parts with very uniform precision are manufactured by an indent method and the press technique has been improved. Upon assembly with an indent method, a deformation force due to the compressive force occurs between the pin and hole and the contact surface is affected by damage. Therefore, a 3 dimensional model was made using the CATIA program and the damage on the surface contacted with indent was estimated through the ANSYS program in this study. In the analysis result, the maximum load applied at the PCB plate was 21.3 N when the pin goes through the PCB plate. When PCB plate came out of the pin, the maximum load was 19.24 N. As the structural analysis result, the maximum equivalent stress of Pin 1 was 192.96MPa because the maximum stress occurs at Pin 1 among all parts of this study model. By examining the damage property of the contacted indent and applying this study result to the design of real indentation, the damage can be prevented and the durability can be estimated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.649-656
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• 2008

The enhancement of the service life of damaged or cracked structures is a major issue for researchers and engineers. The hierarchic void element based on the integrals of Legendre polynomials is used to characterize the fracture behaviour of unpatched crack as well as repaired crack with bonded composite patches by computing the stress intensity factors and stress contours at the crack tip. Since the equivalent single layer approach is adopted in this study, the proposed element is necessary to represent a discontinuous crack part as a continuum body with zero stiffness. Thus the aspect ratio of this element to represent the crack should be extremely slender. The sensitivity of numerical solution with respect to energy release rate, displacement and stress has been tested to show the robustness of zero stiffness element as the aspect ratio is increased up to 2000. The stiffness derivative method and displacement extrapolation method have been applied to calculate the stress intensity factors of Mode I problem. It is noted that the proposed hierarchical void element can be one of alternatives to analyze the patched crack problems.

• Computational Structural Engineering
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• v.3 no.4
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• pp.105-112
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• 1990

A rational and straightforward method is introduced for developing continuum models of large platelike periodic lattice structures based on energy equivalence, The procedure for developing continuum models involves using existing finite element matrices in calculating strain and kinetic energies of a repeating cell. The equivalent continuum plate properties are obtained from the direct comparison of the reduced stiffness and mass matrices for continuum and lattice plates. Numerical results prove that the method developed in this paper shows very good agreement with other well-recognized methods.

• Steel and Composite Structures
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• v.3 no.5
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• pp.307-320
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• 2003

This paper presents an efficient approach to the determination of the buckling loads of down-aisle, spliced, unbraced, pallet rack structures subjected to vertical and horizontal loads. A pallet rack structures is analysed by considering the stability equations of an equivalent free-sway column. The effects of semi-rigid beam-to-upright, splice-to-upright and base-plate-to-upright connections are fully incorporated into the analysis. Each section of upright between successive beam levels in the pallet rack is considered to be a single column element with two rotational degrees of freedom. A computer algebra package was used to determine modified stability equations for column elements containing splices. The influence of the position of splices in a pallet rack is clearly demonstrated.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.05a
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• pp.159-163
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• 1999

A seat frame structure in automotive vehicles made of polymer matrix composite to achieve weight reduction at low cost was developed. In order to design and manufacture the actual product, studies on material selection, and structural analyses were performed. Structural analyses were performed with a finite element analysis. Analyses were done for several cases suggested in various safety regulations of FMVSS(Federal Motor Vehicle Safety Standards). Each result was utilized to modify the actual shape to obtain a lighter, safer and more stable design. The final design was used to produce a sample bottom plate of the seat structure. Substitution of the material resulted in a weight reduction effect with equivalent strength, fatigue and impact characteristics. Furthermore, several effects from the replacement of the material besides weight reduction were also examined.

• Structural Engineering and Mechanics
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• v.63 no.1
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• pp.125-136
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• 2017

This study investigated the performance of a steel column standing on a reinforced concrete footing when it was subjected to collision of an eight-ton single unit truck. Finite element analyses of the structure with different connection schemes were performed using the finite element model of the truck, and the results showed that the behavior of the column subjected to the automobile impact depended largely on the column-footing connection detail. Various reinforcement schemes were investigated to mitigate the damage caused by the car impact. The probability of the model reinforced with a certain scheme to reach a given limit state was obtained by fragility analysis, and the effects of the combined reinforcement methods were investigated based on the equivalent fragility scheme. The analysis results showed that the reinforcement schemes such as increase of the pedestal area, decrease of the pedestal height, and the steel plate jacketing of the pedestal were effective in reducing the damage. As the speed of the automobile increased the contribution of the increase in the number of the anchor bolts and the dowel bars became more important to prevent crushing of the pedestal.