• Computers and Concrete
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• v.15 no.2
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• pp.305-319
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• 2015

On mesoscopic level, concrete can be treated as a three-phase composite material consisting of mortar, aggregates and interfacial transition zone (ITZ) between mortar and aggregate. A lot of research has confirmed that ITZ plays a crucial role in the mechanical fracture process of concrete. The aim of the present study is to propose a numerical method on mesoscale to analyze the failure mechanism of reinforced concrete (RC) structures under mechanical loading, and then it will help precisely predict the damage or the cracking initiation and propagation of concrete. Concrete is meshed by means of the Rigid Body Spring Model (RBSM) concept, while the reinforcing steel bars are modeled as beam-type elements. Two kinds of RC members, i.e. subjected to uniaxial tension and beams under bending, the fracture process of concrete and the distribution of cracks, as well as the load-deflection relationships are investigated and compared with the available test results. It is found that the numerical results are in good agreement with the experimental observations, indicating that the model can successfully simulate the failure process of the RC members.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.131-139
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• 2001

Experimental programs were accomplished to improve and evaluate the structural performance of RC frame structures with masonry infilled wall, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are restraining factors of frame, with or without masonry infilled wall, and masonry method. Six reinforced concrete rigid frame and masonry infilled wall were tested and constructed in one-third scale size under vertical and cyclic loads simultaneously. Based on the test results, the following conclusions can be made. For masonry infilled wall with restraining factors of frame(IFWB-1~3), cumulated energy dissipation capacities were increased by 1.35~1.60 times in comparision with that of masonry infilled wall(IFB-1) at final stage of testing. For masonry infilled wall with restraining factors of frame, maximum horizontal capacities were increased by 1.91~2.24 times in comparision with that of rigid frame.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.9
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• pp.1357-1363
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• 1997

Currently it is increasing to use th bonded dissimilar materials in the various field of advanced engineering such as the highly rigid and lighter vehicle, plastic molding LSI package and metal/ceramic bonded joint. In spite of such a wide application of the bonded dissimilar materials, the evaluation method of the bonding strength has not been established yet. Therefore in this paper we analyze the interface crack problem by introducing fracture mechanics parameters as the basic research about estimating of the strength of adhesive joints. The variation of stress intensity factor according to the elastic modulus of adherend and thickness of bonded layer are investigated. Numerical results are based on the results of boundary element analysis of four different type butt joints subjected to uniaxial tension loading.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.61-72
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• 2011

In this study, the structural details of steel girder-abutment joints with shear connectors and tie bars were suggested to improve the rigid behavior and crack-resisting capacity of the joints in integral bridges. Experimental loading tests of steel girder-abutment joint specimens with the proposed and empirically constructed structural details were carried out, and the capacities and behavioral characteristics of the joints were evaluated through loading tests. Based on the results of the loading tests, it was estimated that all types of tested joints can be applied to the steel girder-abutment joints because they have sufficient stiffness and crack-resisting capacity under the required design and yield loads. According to the initial stiffness, crack propagations, and load-strain relationships, however, the joints with shear connectors and tie bars showed better structural behaviors compared to the empirically constructed joint.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.143-150
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• 1996

This is an explicit-Implicit, finite element analysis for linear as well as nonlinear hygrothermal stress problems. Additional features, such as moisture diffusion equation, crack element and virtual crack extension(VCE ) method for evaluating J-integral are implemented in this program. The Linear Elastic Fracture Mechanics(LEFM) Theory is employed to estimate the crack driving force under the transient condition for and existing crack. Pores in materials are assumed to be saturated with moisture in the liquid form at the room temperature, which may vaporize as the temperature increases. The vaporization effects on the crack driving force are also studied. The Ideal gas equation is employed to estimate the thermodynamic pressure due to vaporization at each time step after solving basic nodal values. A set of field equations governing the time dependent response of porous media are derived from balance laws based on the mixture theory Darcy's law Is assumed for the fluid flow through the porous media. Perzyna's viscoplastic model incorporating the Von-Mises yield criterion are implemented. The Green-Naghdi stress rate is used for the invariant of stress tensor under superposed rigid body motion. Isotropic elements are used for the spatial discretization and an iterative scheme based on the full newton-Raphson method is used for solving the nonlinear governing equations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.431-441
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• 2014

The effects of hull-girder vibration on the fatigue strength of a Post-Panamax container ship are discussed in the present paper. Firstly, the short-term sea states are categorized according to the occurrence probability of each sea state. Time histories of hull-girder stress in short-term sea states are calculated by means of a nonlinear simulation code of ship response assuming that the hull-girder is rigid and flexible. Then, the calculated stress peaks are processed by the rainflow counting method, where two different counting procedures are used based on the considerations of crack propagation behaviors. Finally, the fatigue damage in life time of the ship in each categorized short-term sea state is estimated by means of Miner's rule. Based on the calculated results, the effects of hull-girder vibrations on the fatigue damage are clarified by disaggregated damage from short-term sea state.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.4
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• pp.31-35
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• 2000

The stress state developed in a thin adhesive layer bonded between the semiconductor chip and the leadframe and subjected to a shear loading is investigated. The boundary element method (BEM) is employed to investigate the behavior of interface stresses. Within the context of a linear elastic theory, a stress singularity of type $\gamma^{\lambda=1}$(0<1<1) exists at the point where the interface between one of the rigid adherends and the adhesive layer intersects the free surface. Such singularity might lead to edge crack or delamination.

• Korean Journal of Materials Research
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• v.13 no.1
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• pp.53-58
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• 2003

For the rib materials in PDP(plasma display panel), an effective method to improve the mechanical properties is to form a composite material by reinforcing a glass matrix with rigid fillers, such as alumina and titania powders. In this study, two types of ribs with different volume percent of fillers and with different glass matrix were tested for hardness, Young's modulus with the Berkovich indentation. As a result, cracks appeared around at the load of 1345 mN for the dense type of rib, while porous one endured until 2427 mN without any crack formation. Young's modulus and hardness decreased at the range: 90∼65 GPa, 9∼4 GPa, respectively as a function of indent load. Thus, a new method with nanoindenter represents a possible evaluation method for mechanical properties of barrier ribs.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.197-202
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• 2005

This study started to confirm and prove for the applicability of the dry-process waterproofing system to cover the defects of the wet-process waterproofing system according to weather circumstance, foundation condition and maintenance, etc. This process has triple combined waterproofing system using asphalt sheet, metal sheet, engineering plastic film. It is not influenced by the concrete's crack as the foundation of the roof according to the movement of the building because the waterproofing system is designed for maintaining good quality by absorbing the stress of contraction and expansion that is occurred by the variation of temperature. Ali components used in this process can be recycled environmentally. The superiority of this process proved and reconfirmed through with the investigation of about 130 fields, around 30,000nf for two years.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.653-656
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• 2006

It is necessary for the new material and construction concept to make up for weak point which related to high durability and finish ability to solve exposure limit of exist construction method. This paper is deal with performance test(tier load, anti abrasion, anti impact, permeability, bond test) compositive using for water reacting soft urethane and rigid urethane to improve the exist problem which are crack movement, adhesive on the wet surface, impact and abrasion by tier load. It is getting decreasing demage compare with other exist materials after test by transfer load, movement and impact.