• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.4
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• pp.958-966
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• 1994

The postbuckling compressive strengths of $[0/90/\pm\theta]_s$ composite laminated cylindrical panels with various fiber angles and width-to-length ratios are characterized by the nonlinear finite element method. For the iteration and load-increment along the postbuckling equilibrium path a modified arc-length method in which the effect of failure can be considered is introduced. In the progressive failure analysis the maximum stress criterion and complete unloading model are used. Present finite element results show good agreement with experiments for $[0_3/90]_s$ cylindrical panel and $[0/\pm45/90/]_s$ plate. The postbuckling compressive strength of $[0/90/\pm\theta]_s$ composite laminated cylindrical panel is independent of the initial buckling stress but high in the panel with large value of the bending stiffness in axial direction. In the several cylindrical panels, it is observed that the prebuckling compressive failures occur and result into the collapse before the buckling.

• Steel and Composite Structures
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• v.9 no.6
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• pp.569-584
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• 2009

Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

• Steel and Composite Structures
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• v.36 no.3
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• pp.273-291
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• 2020

Two-storey X-bracings are currently very popular in European practice, as respect to chevron and simple X bracings, owing to the advantages of reducing the bending demand in the brace-intercepted beams in V and inverted-V configurations and optimizing the design of gusset plate connections. However, rules for two-storey X braced frames are not clearly specified within current version of EN1998-1, thus leading to different interpretations of the code by designers. The research presented in this paper is addressed at investigating the seismic behaviour of two-storey X concentrically braced frames in order to revise the design rules within EN1998-1. Therefore, five different design criteria are discussed, and their effectiveness is investigated. With this aim, a comprehensive numerical parametric study is carried out considering a set of planar frames extracted from a set of structural archetypes that are representative of regular low, medium and high-rise buildings. The obtained results show that the proposed design criteria ensure satisfactory seismic performance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.3
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• pp.164-167
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• 2013

The objectives of this paper are to study the performance improvement of waste heat recovery from a boiler, by the Cured-In-Place-Pipe(CIPP) process. The conventional apparatus does not utilize the waste heat from the boiler during the process. However, the present apparatus recovers the waste heat from the boiler. When the new apparatus is used, the bending strength and modulus of the CIPP becomes double, and is over 45% stronger, than the required conditions, respectively. It is found that the energy consumption reduces to 50%, by recovering the waste heat from the boiler, and the oil consumption amount reduces to 1/3, compared to the conventional apparatus.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.301-310
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• 2018

In this paper, a multi-objective multiparameter optimization procedure is developed by combining rigorously developed metamodels with an evolutionary search algorithm-Genetic Algorithm (GA). Response surface methodology (RSM) is used for developing the metamodels to replace the tedious finite element analyses. A nine-node isoparametric plate bending element is used for conducting the finite element simulations. Highly accurate numerical data from an author compiled FORTRAN finite element program is first used by the RSM to develop second-order mathematical relations. Four material parameters-${\frac{E_1}{E_2}}$, ${\frac{G_{12}}{E_2}}$, ${\frac{G_{23}}{E_2}}$ and ${\upsilon}_{12}$ are considered as the independent variables while simultaneously maximizing fundamental frequency, ${\lambda}_1$ and frequency separation between the $1^{st}$ two natural modes, ${\lambda}_{21}$. The optimal material combination for maximizing ${\lambda}_1$ and ${\lambda}_{21}$ is predicted by using a multi-objective GA. A general sensitivity analysis is conducted to understand the effect of each parameter on the desired response parameters.

• Journal of Advanced Marine Engineering and Technology
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• v.12 no.3
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• pp.57-67
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• 1988

Although handicapped by the inability to bridge the size gap between small laboratory sample and large engineering component, the V charpy test sample method does possess certain advantages, such as each of preparation, simplicity of test method, speed, low cost in test machinery, and low cost per test. On the other hand, the COD test method does posses advantages, which reduce the size gap between the laboratory sample and actual engineering component. Consequently, the correlation between V charpy absorbed energy and the critical COD value is required for estimating critical COD value from the simple V charpy test results. In this paper, the high tensile strength steel AH36 plate specimens having a single edge cracked notch were investigated to find out the correlation between V charpy absorbed energy and critical COD value in the welded parts under such various welding methods as shielded metal arc welding, the submerged arc welding and the electro gas welding by means of V charpy impact test and static 3-point bending test. Main results obtained are as follow ; 1. The relationships between V charpy absorbed energy Wc' and critical COD value ($\delta_c$)show; $\delta_c$=0.0065 Wc'+0.1906. 2. Ductile- brittle transition behaviours can be estimated by means of fracture appearance and general yielding behaviours. 3. The V charpy absorbed energy of SMAW is higher than that of SAW, EGW and similar relationships are obtained in the COD tests.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1326-1330
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• 2008

The failure mode of steel road wheels in a vehicle is cracks from ventilation hole through to contact plane on steel wheel's disc plate. But a number of cracks of Cornering Fatigue Limit Test is on contact plane near to wheel nut mounting area, even though it's satisfied with specified cycles. So this paper searches out causes to improve durability and reliability of C.F.T by uni-axial bending moment test. The verified cause is a "fretting" on contact area of steel wheel. In result, this paper suggests a solution to prevent a fretting by inserting a damping shim, 0.7mm between steel wheel contact areas. Therefore this paper makes it possible to move crack position of C.F.T in steel wheel from contact plane to vehicle's failure mode.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1061-1066
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• 2016

Corrugation of a corrugated panel dramatically increases the bending stiffness per weight. However, corrugated panels show lower sound insulation performance than that of the flat plate having the same weight. Especially, in a particular frequency region, the sound transmission loss significantly decreases. Main reason of the problem is known as the local resonance. A number of local resonance modes occur above a certain frequency band and modal density rapidly increases. In this study, we investigate the relation of the sound transmission loss and the modal density. Finally, we propose a design methodology in terms of the modal density to improve the sound insulation performance of the corrugated panels without weight increase.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.115-122
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• 2004

The objective of the present study is to understand the strengthening effects of reinforced concrete beam applied the reinforced plates, expended metal and carbon fiber grid with the ceramic metal. In the present study, the bending tests are performed to understand the increasing effects of stiffness and ductility for the strengthening RC beam. Also, the important purpose of the structural tests is to understand the adhesion performance of the ceramic metal. It is expected the present experimental observations as a valuable source in suggestion improved the strengthening method more than this method by analysis of the failure mode for the specimens.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.17-24
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• 1992

It would be much effective that single column type pier is used in concrete slab bridges rather than ${\Pi}$ or gravity type pire is used. To determine the longitudinal benging moment in concrete slab bridges supported by single column type piers, the concept of effective width is applied. By elastic plate theory cooperated with finite element method, the distribution of the longitudinal moment of the slab supported by single column type piers is studied. The main variables are span, width. thickness of the slab, and column section size. The analytical results obtained are summarized and analysed to evaluate the maximum longitudinal negative moment, then a simplified method for calculating the longitudinal moment is proposed.