• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.39-48
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• 1989

The concrete temperature in mass concrete rises rapidly above the placing temperature owing to the heat given off by the hydrating cement. This temperature rise produces tensile stress and cracks which later become the cause of water leakage in concrete structures. It is essential, therefore, to reduce the interior heat of concrete dam given off by hydrating cement by artificial cooling. The present study aiming to study the temperature variations in mass concrete by pipe cooling, compars the actual measurements of Chungju Dam with the temperature calculated by Finite Difference Method(FDM), and it found that the results closely agree with each other. Based on these results, the analyses are performed simulate the interior temperature history of concerte dam made of type II (moderate heat) portland cement under various coditions.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.469-477
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• 2006

Models to predict the ultimate strength of simply supported or continuous deep beams with web openings are proposed. The derived equations are based on upper-bound theorem. The concrete is assumed as a perfectly plastic material obeying the modified Coulomb failure criteria with zero tension cutoff. Reinforcing bar is considered as elastic-perfectly plastic material and its stress is calculated from the limiting principal compressive strain of concrete. The governing failure mechanisms based on test results are idealized as rigid moving blocks separated by a hyperbolic yield line. The effective compressive strength of concrete is calculated from the formula proposed by Vecchio and Collins. Comparisons with existing test results are performed, and they show good agreement.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.71-78
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• 1998

Recently, modern long-stroke diesel engines with small number of cylinders have been installed for energy saving and simpler maintenance. These kinds of low speed diesel engine produce large torsional vibration in the shafting, which induces the excessive vibratory stresses in the shafting and large propeller thrust variation. This thrust variation excites vibrations of the shafting and superstructure in the longitudinal direction. Up to now the deteriministic analysis of coupled vibration of marine shafting system has been performed. In this paper probabilistic analysis method of the marine diesel propulsion shafting system under coupled axial and torsional vibrations is presented. For the purpose of this work, the torsional and axial vibration excitations of engine and propeller are assumed to be probabilistic while the lateral excitation is assumed to be deterministic. The probabilistic analysis is based on a response surface and Monte-Carlo simulation. Numerical results based on the proposed method are compared with results calculated using the conventional deterministic analysis method. The results obtained make it clear that the proposed method gives a substantial increase in information about shafting behaviour as compared with the deterministic method.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.355-365
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• 2009

This paper proposes an elasto-plastic finite difference method which is useful for the stability evaluation of concrete lining installed in a deep circular tunnel. Mohr-Coulomb criterion is assumed for the condition of yielding in both the rock mass and concrete lining. In order to take into account the installation delay of lining after the excavation, the outer boundary pressure acting on the lining was calculated with the consideration of the convergence occurred before the lining installation. The distributions of stress and displacement in the rock mass and lining were calculated based on the method proposed Lee & Pietruszczak (2008). The applicability of the proposed method was demonstrated by conducting the elasto-plastic analysis of concrete lining supporting an imaginary compressed air storage tunnel. The analysis result revealed that the exact determination of the boundary pressures acting on the concrete lining is of importance in the stability analysis of concrete lining.

• Journal of Korean Society of Steel Construction
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• v.12 no.4 s.47
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• pp.387-395
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• 2000

The purpose of this research is to evaluate the capacity of strength and plastic deformation of those members, and provide experimental data on the seismic behavior of these members as a basis for developing guidelines for designing seismically resistant concrete-filled steel tubular columns. Eighteen cantilever-type specimens were tested under constant axial load and cyclically lateral load as models of bottom columns in high-rise building. The parameters studied in the test program included, are width-thickness ratio of steel tube, slenderness ratio (Lo/D) and axial force ratio. From the test results, the effects of parameters on the strength, the deformation capacity, energy absorption capacity are discussed. The specimen flexural capacity under combined axial and lateral loading was found to be almost accurately predicted by criteria AIJ and AISC-LRFD providing conservative results. Therefore KSSC for encased composite column can be applied to the concrete filled column if composite section and elastic modulus are modified according to AIJ and AISC-LRFD. Finally, the proposed flexural capacity considering confinement effects is a food agreement on the tests results.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.613-625
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• 2002

This paper aimed to investigate the damage process of steel parts experiencing failure under strong repeated loading. Likewise, a damage index using various factors related to the damage was proposed. An analysis method for evaluating the damage state was also developed. The damage assessment method focused on the local strain history at the cross-section of the heaviest concentration of deformation. Cantilever-type steel parts were analyzed under uniaxial load combined with a constant axial load, considering horizontal displacement history, Loading patterns and steel types were considered as the main parameters in analyzing the models. The effects of the parameters on the failure modes, deformation capacity, and damage process as seen from the analysis results were also discussed. Each failure process was compared as steel types. In addition, the failure of steel parts under strong repeated loading was determined according to loading. Results revealed that the state of the failure is closely related to the local plastic strain.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.10
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• pp.1229-1235
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• 2011

Fatigue tests were conducted on the aluminum alloy, A7075-T6 to determine the most reliable fretting fatigue damage parameter. Specimens with grooves were used, so that either fretting fatigue crack at the pad/specimen interface or plain fatigue crack at the groove could be nucleated, depending on the pad pressure. Both the crack nucleation location and initial crack orientation were examined using optical microscopy, and the results were used to assess the reliability of the various fretting fatigue damage parameters that have been most commonly used in the literature. Finite element analysis was employed to obtain the stress and strain data of the specimen, which were needed to estimate the parameter values and the orientation of the critical plane. It was revealed that both the Fatemi.Socie and McDiarmid parameters, which assume shear-mode fatigue cracking, are the most reliable.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.1
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• pp.92-98
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• 1991

The structures such as railway bridges can be modelled as the multi-span beam on the elastic foundation. These structures are usually subject to the moving load, which has a great effect on dynamic stresses and can cause severe motions, especially at high velocities. In this paper, the dynamic responses of the multi-span beam on the elastic foundation were obtained by using the Galerkin's method and the numerical time integration technique. As trial functions, the same orthogonal polynomial functions obtained in part 1, were used. From the numerical results, it was found that the one term expansion of the assumed solution usually leads to the accurate solutions. However, in the case that the stiffness of the transnational spring is very high or the rotational spring is placed where the slope of the first mode is zero, the higher modes must be included to obtain the accurate solutions.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.149-154
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• 2008

We analyzed the Coulomb stress transfer near a small-scale reverse fault. For the modeling we used the geometry of a Quaternary fault in Gyeongju area, Eupcheon fault. For an assumed reverse faulting slip of 10cm, the resulting values of the Coulomb stress change are relatively higher (>2 bar) near the edges (both downward and lateral) of the fault, and diminish slightly upward and downward. The equivalents are negative in the zone immediately below and above the fault, exhibiting a "T" shape of low stress zone in the vertical profile of the fault. This study demonstrates the possible ranges and directions the aftershock energy would propagates after a reverse faulting.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.249-252
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• 2008

A study for the nonlinear analysis method of RC(Reinforced Concrete) beams with unbonded prestressing CFRP plate is presented. The cross-section of RC beam element is idealized as an assemblage of concrete and reinforcing steel fibers in order to account for varied material properties within the cross-section of the element. The unbonded CFRP plate is modeled as a series of the CFRP plate segments each of which is linked to the RC beam element, but slips without any resistance to simulate the unbonded behavior of the CFRP plate. The stress of each CFRP plate segment is redistributed iteratively using the force equilibrium relationship at each common node until it reaches at the same stress level. To evaluate the validity of the proposed analysis method, the results of ultimate analysis of the reinforced concrete beams with unbonded prestressing CFRP plates are compared with the experimental results obtained from other investigators. The proposed analysis method is found to predict ultimate behaviors of these beams fairly well.