• Steel and Composite Structures
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• v.45 no.4
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• pp.501-511
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• 2022

In this study, a two-dimensional model of the contact problem has been examined using the finite element method (FEM) based software ANSYS and based on the multilayer perceptron (MLP), an artificial neural network (ANN). For this purpose, a functionally graded (FG) half-infinite layer (HIL) with a crack pressed by means of two rigid blocks has been solved using FEM. Mass forces and friction are neglected in the solution. Since the problem is analyzed for the plane state, the thickness along the z-axis direction is taken as a unit. To check the accuracy of the contact problem model the results are compared with a study in the literature. In addition, ANSYS and MLP results are compared using Root Mean Square Error (RMSE) and coefficient of determination (R2), and good agreement is found. Numerical solutions are made by considering different values of external load, the width of blocks, crack depth, and material properties. The stresses on the contact surfaces between the blocks and the FG HIL are examined for these values, and the results are presented. Consequently, it is concluded that the considered non-dimensional quantities have a noteworthy influence on the contact stress distributions, and also, FEM and ANN can be efficient alternative methods to time-consuming analytical solutions if used correctly.

• Journal of the Korean Wood Science and Technology
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• v.40 no.5
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• pp.343-351
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• 2012

A large diameter roundwood is an important element of Korean traditional buildings, Hanok, and is hard to be dried without surface cracks. Four different pretreatments, such as pre-cracking, oil heating, kerfing-oil heating and PEG impregnation, were investigated for reducing the surface cracks of large-diameter roundwood specimens during heat treatment. The roundwood specimens of pre-cracking, oil heating and kerfing-oil heating showed surface cracks during pretreatment, but that of PEG impregnation did not. It was confirmed that kerfing reduced the total crack width. Among the four pretreatments and control only the PEG impregnation roundwood specimen had no crack on both outer and inner surfaces after heat treatment. The PEG impregnation specimen shrank only 1.6% in the tangential direction while the pre-cracking did 8.0%.

• Journal of the Korea Concrete Institute
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• v.11 no.6
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• pp.79-88
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• 1999

In this paper, the electro-deposition method for the rehabilitation of cracked concrete, based on the electro-chemical technique, is presented. The main purpose of this paper is to apply this technique to reinforced concrete members on land. After cracking with a specified load(crack width 0.5mm), 10$\times$10$\times$20cm concrete specimens with embedded steel bars were immersed in several solutions, then a constant current density between the embedded steel in concrete and an electrode in the solution was applied for 4~20 weeks. The results indicate that electro-deposits formed in this process are able to close concrete cracks and to coat the concrete surface and that formation of these electro-deposits is confirmed to have an effect of protection against detrimental materials. Therefore, it is demonstrated that the electro-deposition method can be usefully applied for the rehabilitation technique of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.202-207
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• 1992

The objective of this study is to develop analytical techniques of polymer impregnated concrete flexural members for its proper applications. crystalline methylmethacrylate(MMA) is chosen as a monomer of polymer impregnants, On the basis of members. fracture toughness, fracture energy , critical crack width, and tension softening relations near crack tip are formulated in terms of member depth, initial notch length and the flexural strength of normal concrete. The structural analysis rocedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. It is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.319-323
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• 1998

Plastic shrinkage cracking is a major concern for concrete, especially for flat structures as highway pavement, slabs for parking garages, and walls. One of the methods to reduce the adverse effect of plastic shrinkage cracking is to reinforced concrete with short randomly distributed fibers. The contribution of cellulose fiber to the plastic shrinkage crack reduction potential of cement composites and its evaluation are presented in this paper. The effects of differing amounts of fibers(0.9kg/㎥, 1.3kg/㎥, 1.5kg/㎥) were studied. The results of tests of the cellulose fiber reinforced concrete were compared with plain concrete and polypropylene fiber reinforced concrete. Results indicated that cellulose fiber reinforcement showed an ability to reduce the total area and maximum crack width significantly(as compared to plain concreted to plain concrete and polypropylene fiber concrete).

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.345-350
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• 2001

Reinforced concrete is, in general, known as a high durability material due to a strong alkalinity of cement. Probable concrete cracks could incur steel corrosion of RC structures and then could easily deteriorate the concrete durability, which can be fully secured by a systematic quality control for the construction of concrete structures. For the corrosion protection of reinforcing steels in concrete, however, current design specifications of concrete cover depth do not in-depth consider the effect of the cracks as well as the chloride content of RC structures. Therefore, appropriate provisions for concrete cover depth should be coded by considering the influence of concrete cracks on the corrosion of reinforcing steels. The objective of this research is to investigate pertinent cover depth, which can prohibit rebar corrosion, on the basis of experimental corrosion measurements of reinforcing steels on crack characteristics such as the width, depth and frequency of concrete cracks.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.156-159
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• 2004

The intention of this study is to reduce the plastic shrinkage of the polymer modified cement mortar using the PVA fiber. The durability of PVA fiber reinforced polymer cement mortar was also evaluated. The test results of PVA fiber reinforced polymer modified cement mortar were compared with plain polymer modified cement mortar(non-fiber). In conclusion, PVA fiber reinforced polymer modified cement mortar showed an ability to reduce the total crack area and maximum crack width significantly. Also. fiber reinforced polymer modified cement mortar show improved durability performance.

• Journal of the Korean Society of Safety
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• v.17 no.2
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• pp.1-7
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• 2002

In this paper, the maximum minimum strain energy density criterion was applied to the mixed mode fatigue test of A5052 H34 alloy. In this study result we can have seen that the authors stress intensity factor for the finite width specimen and method of determining testing load, based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E-647-95, is useful.

• Computers and Concrete
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• v.13 no.3
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• pp.389-409
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• 2014

Precast hollow core slabs (HCS) are technically advanced products in the precast concrete industry, widely used in the last years due to their versatility, their multipurpose potential and their low cost. Using three dimensional FEM (Finite Element Method) elements, this study focuses on the stresses induced by the prestressing of steel. In particular the investigation of the spalling crack formation that takes place during prestressing is carried out, since it is important to assure the appropriate necessary margins concerning such stresses. In fact, spalling cracks may spread rapidly towards the web, leading to the detachment of the lower part of the slab. A parametric study takes place, capable of evaluating the influence of the tendon position and of the web width on the spalling stress. Consequently, after an extensive literature review on the topic of soft computing, an optimization of the HCS is performed by means of Genetic Algorithms coupled with 3-D FEM models.

• Structural Engineering and Mechanics
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• v.58 no.2
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• pp.301-326
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• 2016

An optimization method of patch shape was developed in this study, in order to improve repair of cracked plates. It aimed to minimize three objectives: stress intensity factor, patch volume and shear stresses in the adhesive film. The choice of these objectives ensures improving crack repair, gaining mass and enhancing the adhesion durability between the fractured plate and the composite patch. This was a multi-objective optimization combined with Finite elements calculations to find out the best distribution of patch height with respect to its width. The implementation of the method identified families of optimal shapes with specific geometric features around the crack tip and at the horizontal end of the patch. Considerable mass gain was achieved while improving the repair efficiency and keeping the adhesive shear stress at low levels.