• Composites Research
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• v.20 no.6
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• pp.21-27
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• 2007

Low-velocity impact damage in a composite stiffened panel was detected using built-in piezoelectric active sensor arrays. Using these piezoelectric active sensors, various diagnostic signals were generated to propagate Lamb waves through the structure and the responses were picked up to detect changes in the structure's vibration signature due to the damage. Three algorithms - ADI(Active Damage Interrogation), TD RMS (Time Domain Root Mean Square) and STFT (Short Time Fourier Transform) - were examined to express the features of the signal changes as one damage index. From damage detecting tests, two impact induced delaminations were detected and the location was estimated with the algorithms and diagnostic signals.

• Journal of the Korean Institute of Rural Architecture
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• v.7 no.1
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• pp.129-136
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• 2005

In this paper, barrier panels against falling stones have been studied experimentally with various specimens. Test results show that stiffened barrier panels show more sufficient capacity than unstiffened barrier. Each type barrier panel can be used for various situations. New barrier panel is good for increasing strength and improving environment and maintaining cost down.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1003-1006
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• 2003

In recent years, FRP plates have been studied for flexural reinforcement of RC structures due to easy installation and good Quality control. This study presents experimental field test results for the effectiveness of flexural reinforcement of the RC slab using external prestressing with thin CFRP strips made by the pultrusion process. It was demonstrated that flexural strength was considerably increased with relatively easy installation when compared to the other methods used for the composite reinforcement.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.174-180
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• 1985

A new measuring technique for the rigidities of stiffened plated is presented. The equations relating the rigidities of stiffened plates and the natural frequencies of a cantilever plate are derived and the rigidities are determined using the measured natural frequencies of the plate. The static deflection tests are conducted for checking the validity of this method. For unstiffened plates the measured rigidities are good agreement with the theoretical values and the experimental results of deflection tests. In the case of stiffened plates the measured rigidities closely matched with the results of deflection tests. It has been also demonstrated that this measuring technique can be utilized in determining the rigidities of arbitrarily stiffened plates.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.167-174
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• 2006

The purpose of this paper is to analyse and compare experimentally flexural behavior of RC beams strengthened with CFRP plates by different methods, which are divided into three classes: externally-bonded without end anchorage, externally-bonded with end anchorages, and anchored after prestressing of CFRP plates. Test results show that the RC beams strengthened with end anchorages have the improvement of ductility and flexural performance evaluation including ultimate strength and deflection, compared with only external bonding. Especially, RC beams with prestressed and anchored CFRP plates increase ultimate strength and ductility significantly.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.74-82
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• 2017

Localized corrosions damages in their structural sections can be occurred affected by installed environment conditions with high temperature as near the coastline and humidity or their poor maintenance situation. In bearing supports of steel bridges, especially, lower web and vertical stiffener in end girder support can be easily corroded because of relatively higher humidity due to the narrow space in the end of girder and the wetted accumulated sediments affected by rain water or antifreezing admixture leaked from expansion joint. It can be related to change in their structural performance. In this study, thus, bearing strength test specimens were fabricated considering corrosion damage in the web and vertical stiffeners and the change in their bearing strengths were experimentally evaluated. From the test results, localized corrosion damage of structural members in the end girder affected the bearing strength of end girder support, especially, localized corrosion damage of the vertical stiffener relatively highly affected their bearing strengths.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.191-198
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• 2010

This study investigated that the stress reduction of single edge cracked plates with patch repairs according to different type of patching such as material, size and thickness of patch and adhesive as well as single sided or double sided patches. As a numerical tool, the p-convergent partial layerwise model has been employed. The proposed model is formulated by assuming piecewise linear variation of in-plane displacement and a constant value of out-of-plane displacements across thickness. The integrals of Legendre polynomials are chosen to define displacement fields and Gauss-Lobatto numerical integration is implemented in order to directly obtain maximum values occurred at the nodal points of each layer without other extrapolation techniques. Also, total strain energy release rate method is adopted to obtain stress intensity factors. Numerical examples are presented not only to demonstrate the stress reduction effect in terms of non-dimensional stress intensity factor and deflection with respect to different type of patch repairs, but also the accuracy of proposed model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.197-208
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• 2000

Choi et al./sup 1)/ presented the total Lagrangian formulation based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account the second order rotation terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome the shear locking phenomena and to eliminate the spurious zero energy mode. In this paper, for the ultimate strength analysis of stiffened shell structures considering effects of residual stresses, the return mapping algorithm based on the consistent elasto-plastic tangent modulus is applied to anisotropic shell structures. In addition, the load/displacement incremental scheme is adopted for non-linear F.E. analysis. Based on such methodology, the computer program is developed and numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with the results in literatures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1A
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• pp.39-48
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• 2012

This study deals with numerical determination of stress intensity factors of adhesively patch-repaired plates with cracks at V-shaped or semicircular notches. The p-convergent anisoparametric model are considered and then three-dimensional virtual crack closure technique is presented using formulations of anisoparametric elements. In assumed displacement fields of an element, strain-displacement relations and three-dimensional constitutive equations are derived with three-dimensional hierarchical shape functions expanded from one-dimensional Lobatto functions. Transfinite mapping technique is used to represent a circular boundary. The present model provides accuracy and simplicity in terms of stress concentration factor, stress distribution, the number of degrees of freedom, and non-dimensional stress intensity factor as compared with previous works in literatures. Stress intensity factors obtained by the three-dimensional virtual crack closure technique are estimated with respect to the variation of width of finite plate, radius of notch root, angular inclination of V-shaped notch, and crack length.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.71-79
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• 2011

Korean national highway has been increased 2 times more for the past ten years because of many highway geometric improvements and new routes since 2000. According to the reasons, maintenance cost has been increased continuously. Deterioration of concrete bridge decks caused by asphalt pavement deformation occupies a high proportion of overall bridge management budget. The number of current highway bridges has reached over 7,800 in 2011, and It is difficult to determine to some future budget. This study predicted the remaining life of concrete bridge decks using the reliability analysis based on Weibull distribution. and The expected future maintenance cost was estimated.