• Computational Structural Engineering
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• v.9 no.4
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• pp.117-126
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• 1996

Damage detection methods using structural tests can be divided into two methods, i.e., static and dynamic. The static methods which use the stiffness properties of the structure are simpler than the dynamic methods. However, static approaches are very sensitive to the displacement measurement noises and modeling errors. The dynamic methods also have limitations in acquiring the natural frequencies and mode shapes of the high frequencies. In this study, a method for the structural damage assessment using sensitivity matrices is developed, in which the drawbacks of the static and dynamic methods can be compensated. Based on the measurement data for the static displacements and dynamic modal properties, the damage locations and the degree of damage are determined using the presented sensitivity matrix method. The efficiency of the proposed method has been examined through numerical simulation studies on truss type structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.32-38
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• 2001

This paper presents an approximate synthesis of 5-SS multi link suspension for 2 D.O.F motions. In the proposed synthesis method, alteration curves of camber, toe, kingpin and caster angles are optimized during the bump rebound and the steering motions. And joint positions can be located within desired boundari es. Especially, steering motions are considered for control of kingpin offset and caster trail. Prescribed motions contain both wheel center positions and imaginary kingpin axes in the multi link type suspension. Constraint equations are formulated with di splacement matrix and velocity matrix using instantaneous screw axis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.859-864
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• 2008

The dynamic interaction between the moving mass and the rotating Timoshenko shaft is investigated. The moving speed of the mass is presented by a constraint equation related to the rotating speed of the shaft. The dimensionless equations of motion for the rotating shaft with a moving mass by using the Timoshenko's beam theory. The dynamic responses of this system are studied. influences of dimensionless parameters such as the rotating speed ratio. the Rayleigh coefficient and the dimensionless axial force are discussed on the transient response and the maximum deflection of the moving system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2672-2679
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• 2000

In synthesizing and RSSS-SC mechanism that is the kinematic model of the McPherson strut suspension system in automobiles, the design equations for R-S, S-S and S-C dyads should be solved separately for a given set of prescribed positions. The number of prescribed positions that the RSSS-SC mechanism can be synthesized is up to three because of the S-C dyad. This limitation may cause unsatisfactory results in synthesized joint positions. This paper presents a kinematic synthesis method to place the joints of an RSSS-SC mechanism in desired boundaries by varying the prescribed positions of the mechanism within acceptable tolerances. The sensitivity analysis of the joint positions is used determine which displacement parameter should be altered to fulfill this task.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2665-2671
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• 2000

Dimensional Synthesis, which is apart of kinematic synthesis, is to determine the dimensions of a mechanism of preconceived typer for a specified task and prescribed performance. In this paper, in an effort to provide designers with flexibility, a dimensional approximate synthesis method is presented for utilizing prescribed tolerance both the displacement and joint positions of a mechanism to be synthesized. For this, a constrained optimization problem is formulated with displacement parameters and joint positions as variables. The proposed method is applied to the synthesis of a 5-SS multi link suspension mechanism. The method discussed here, however, can be easily applied to any mechanism of which the kinematic constraint equations can be derived.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.201-207
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• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.

• Journal of the Korean Geotechnical Society
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• v.38 no.7
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• pp.49-62
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• 2022

The hollow modular concrete block reinforced foundation method is one of the ground reinforcement foundation methods that uses hexagonal honeycomb-shaped concrete blocks with mixed crushed rock to reinforce soft grounds. It then forms an artificial layered ground that increases bearing capacity and reduces settlement. The hollow modular honeycomb-shaped concrete block is a geometrically economical, stable structure that distributes forces in a balanced way. However, the behavioral characteristics of hollow modular concrete block reinforced foundations are not yet fully understood. In this study, a bearing capacity test is performed to analyze the reinforcement effectiveness of the hollow modular concrete block through the laboratory model tests. From the load-settlement curve, punching shear failure occurs under the unfilled sand condition (A-1-N). However, the filled sand condition (A-1-F) shows a linear curve without yielding, confirming the reinforcement effect is three times higher than that of unreinforced ground. The bearing capacity equation is proposed for the parts that have contact pressure under concrete, vertical stress of hollow blocks, and the inner skin friction force from horizontal stress by confining effect based on the schematic diagram of confining effect inside a hollow modular concrete block. As a result of calculating the bearing capacity, the percentage of load distribution for contact force on the area of concrete is about 65%, vertical force on the area of hollow is 16.5% and inner skin friction force of area of the inner wall is about 18.5%. When the surcharge load is applied to the concrete part, the vertical stress occurs on the area of the hollow part by confining effect first. Then, in the filled sand in the hollow where the horizontal direction is constrained, the inner skin friction force occurs by the horizontal stress on the inner wall of the hollow modular concrete block. The inner skin friction force suppresses the punching of the concrete part and reduces contact pressure.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.4
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• pp.237-247
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• 1997

A geometrical inverse heat conduction problem is solved for the infrared scanning cavity detection by the boundary element method using minimal energy technique. By minimizing the kinetic energy of temperature field, boundary element equations are converted to the quadratic programming problem. A hypothetical inner boundary is defined such that the actual cavity is located interior to the domain. Temperatures at hypothetical inner boundary are determined to meet the constraints of mea- surement error of surface temperature obtained by infrared scanning, and then boundary element analysis is peformed for the position of an unknown boundary (cavity). Cavity detection algorithm is provided, and the effects of minimal energy technique on the inverse solution method are investigated by means of numerical analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.141-149
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• 2005

This paper deals with formulations of the energy equilibrium equation by an introduction of the algebraic description, quarternion, which meets conservations of system energy for the equation of motion. Then the equation is discretized to analyze the dynamits analysis of flexible multibody systems in such a way that the work done by the constrained force completely is eliminated. Meanwhile, Rodrigues parameters we used to express the finite rotation lot the proposed method. This method lot the initial essential step to a guarantee of developments of the 3D dynamical problem provides unconditionally stable conditions for the nonlinear problems through the numerical examples.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.55-62
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• 2003

Subdomain-interface variational formulation is presented to solve a class of dynamic contact problems of composite structures. The penalty method is used for imposing inequality constraints on contact surfaces and for connecting finite element subdomains that satisfy interface compatibility conditions. As a result, any complex-shaped domain can be easily divided into independently modeled subdomains without considering the conformity of meshes on interfaces. Some advantageous features of the present method are shown through a set a numerical studies with a developed computer code.