• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.291-302
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• 2018

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.769-777
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• 2015

In this study, the rheological models were introduced and developed to reflect rate dependent tensile behaviour of concrete. In general, mechanical properties(e.g. strength, elasticity, and fracture energy) of concrete are increased under high loading rates. The strength of concrete shows high rate dependency among its mechanical properties, and the tensile strength has higher rate dependency than the compressional strength. To simulate the rate dependency of concrete, original spring set of RBSN(Rigid-Body- Spring-Network) model was adjusted with viscous and friction units(e.g. dashpot and Coulomb friction component). Three types of models( 1) visco-elastic, 2) visco-plastic, and 3) visco-elasto- plastic damage models) are considered, and the constitutive relationships for the models are derived. For validation purpose, direct tensile test were simulated, and characteristics of the three different rheological models were compared with experimental stress-strain responses. Simulation result of the developed visco-elasto-plastic damage(VEPD) model demonstrated well describing and fitting with experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.961-966
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• 2001

The schematic design process is formulated to develop the vibroisolating rubber mount in optical disc drives. The dynamic model of vibration isolation system is established by using a rigid body with 6 degree of freedom and linear springs with damping property. Considering the practical vibration condition of DVDP(Digital Versatile Disk Player), the required properties of vibroisolating rubber mounts are investigated. Also finite element model of a vibroisolating rubber mount is used to obtain shape design concept and identify the characteristics of a rubber mount which satisfies the required properties from previous design stage. Finally the evaluation method of dynamic properties of vibroisolating rubber mounts is established by utilizing modal test method. Based on the developed process, vibroisolating rubber mounts with a good performance have been developed.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.45-50
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• 2002

Airbag systems have improved the occupant safety in reducing the injuries of driver and passenger during collisions. They have occasionally caused fatalities; especially to small occupant and children. Recent airbag related fatalities of children have raised serious concerns on how to evaluate the safety of children in various crash environments. This paper present the development of the 3-year-old human model. Child human model is composed of skin, skeleton and joints. The positions of joint and mass properties of body segments are calculated from ARB(Ariticulated Rigid Body) program GEBOD. To verify the developed human model, ROM simulation and OOP simulations are conducted.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.19-27
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• 2001

In this seismic analyses of structures, it is well recognized that the effects of soil-structure interaction can not be ignored and seismic responses of a structure taking into account the stiffnesses of a foundation-soil system show the significant difference from those with a rigid base. However, current seismic analyses of apartment building structures were carried out with the rigid base ignoring the characteristics of the foundation and the properties of the underlying soil. In this study, seismic analyses of wall-slob type apartment buildings which have a particular structural type were carried out taking into account the soft soil layer comparing seismic response spectra of a flexible base with those of a rigid base and UBC-97. Low-rise or middle height wall-slab type apartment buildings built on the deep soft soil layer showed a rigid body motion with the reduced seismic responses due to the base isolation effect, indicating that it is considerably safe but uneconomical to utilize the design spectra of UB-97 for the seismic design of wall-slab type apartment buildings due to conservative design.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.441-446
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• 2002

We have presented the results of thermodynamic, structural and dynamic properties of liquid benzene, toluene, and p-xylene in canonical (NVT) ensemble at 293.15 K by molecular dynamics (MD) simulations. The molecular model adopted for these molecules is a combination of the rigid body treatment for the benzene ring and an atomistically detailed model for the methyl hydrogen atoms. The calculated pressures are too low in the NVT ensemble MD simulations. The various thermodynamic properties reflect that the intermolecular interactions become stronger as the number of methyl group attached into the benzene ring increases. The pronounced nearest neighbor peak in the center of mass g(r) of liquid benzene at 293.15 K, provides the interpretation that nearest neighbors tend to be perpendicular. Two self-diffusion coefficients of liquid benzene at 293.15 K calculated from MSD and VAC function are in excellent agreement with the experimental measures. The self-diffusion coefficients of liquid toluene also agree well with the experimental ones for toluene in benzene and for toluene in cyclohexane.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.185-191
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• 2003

A numerical study on the hydrodynamic properties of a floating flexible breakwater consisting of triple vertical porous membrane structures attached to a floating rigid pontoon restrained by moorings is carried out in the context of two-dimensional linear wave-flexible body interaction theory. The tensions in the triple membranes are achieved by hanging a clump weight from its lower ends. The clump weight is also restrained properly by moorings. The dynamic behavior of the breakwater was described through an appropriate Green function, and the fluid multi-domains are incorporated into the boundary integral equation. Numerical results are presented which illustrate the effects of the various wave and structural parameters on the efficiency of the breakwater as a barrier to wave action. It is found that the wave reflection and transmission properties of the structures depends strongly on the membrane length taking major fraction of water column, the magnitude of tensions on membrane achieving by the clump weight, proper mooring types and stiffness, the permeability on the membrane dissipating wave energy.

• Journal of the Korean Ceramic Society
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• v.29 no.8
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• pp.623-629
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• 1992

The possible use of bioglass as implant materials is due to its biocompatibility to human body. Even if many animal studies for the bioglasses have been performed, their compositional dependences of structures and physical properties are not fully understood. In the present work, physical property measurements such as density and thermal expansion coefficient were carried out for the bioglasses, with substitution of CaO for Na2O in bioglass composition (46.1%SiO2, 24.4%Na2O, 26.9%CaO, 2.6%P2O5:mol%). Hydroxyapatite formation on the glass surface was also examined after reacted in Tris-buffer solution. As CaO was substituted for Na2O, the bond strength between nonbridging oxygen and modifier became stronger to make glass structure rigid, and resulted in increase in density and decrease in thermal expansion coefficient. When the bioglasses were reacted in Tris-buffer solution, hydroxyapatite was formed on the bioglass surface for all prepared glasses in 2 hours, independently on CaO content, and the thickness of hydroxyapatite layer was decreased a little, while the thickness of SiO2 rich layer was decreased sharply with CaO content.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.1883-1897
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• 1993

Interactive computer-aided analysis of mechanical systems has recently been undergoing an evolution due to highly efficient computer graphics. The industrial implementation of state-of-the-art analytical developments in mechanisms has been facilitated by computer-aided design packages because these rigid-body mechanism analysis programs dramatically reduce the time required for linkage design. This paper proposes a component modular approach to computeraided kinematic motion analysis for general planar multiloop mechanisms. Most multiloop mechanisms can be decomposed into serveral components. The kinematic properties (position, velocity, and acceleration) of every node can then be determined from the kinematic analysis of the corresponding component modules by a closed-form solution procedure. In this paper, 8 types of modules are defined and formulations for kinematic analysis of the component modules are derived. Then a computer-aided kinematic analysis program is developed using the proposed approach and the solution procedure of an example shows the effectiveness and accuracy on the approach.

• Structural Engineering and Mechanics
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• v.11 no.2
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• pp.211-219
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• 2001

This paper presents the tangent stiffness method for 3-D geometrically nonlinear folding analysis of a reversal arch. Experimental tests are conducted to verify the numerical analysis. The tangent stiffness method can accurately evaluate the geometrical nonlinearity due to the element translating as a rigid body, and the method can exactly handle the large rotation of the element in space. The arch in the experiment is made from a thin flat bar, and it is found that the folding process of the arch may be captured exactly by the numerical analysis with a model consisting of only 18 elements with the same properties.