• Composites Research
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• v.12 no.4
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• pp.25-32
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• 1999

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross sections and with arbitrary boundary conditions was developed and reported by Kim, D. H. in 1974. In this paper, the result of application of this method to the special orthotropic plates on elastic foundation with free boundaries is presented. Such plates represent the concrete highway slab and hybrid composite pavement on bridges. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation and the aspect ratio of the plate on the natural frequency is thoroughly studied. The effect of neglecting the mass of the plates on the natural frequency, as the ratio of the point mass/masses to the plate mass increases, is also studied, in deep.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.233-239
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• 2002

Reinforced concrete deck slabs are directly affected by traffic loads and they are also susceptible to weather-related problems, such as cracking, reinforcement corrosion, spatting, scaling, delamination, leakage, efflorescence and so on. Some of these defects are caused by water which seeps through pavements and trapped between pavements and deck slabs. For durability of reinforced concrete deck slabs and pavements, it is very important to protect deck slabs and drain the trapped water out. To develop the trapped water drainage system, the following studies have been performed in Korea Highway Cooperation: related researches a re reviewed; for six bridges, deck slabs are thoroughly investigated; new system to effectively drain the trapped water out is proposed; the proposed system is installed and evaluated. The proposed system is proved to be effective to drain the trapped water out and is expected to increase the durability of reinforced concrete deck slabs.

• Journal of the Korean GEO-environmental Society
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• v.15 no.7
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• pp.23-30
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• 2014

This paper deals with the characteristics of deformation of the underground corrugated steel plate culverts constructed in the areas where the minimum depth of within 1.5 m soil cover is not secured in the bottom of highways. The underground corrugated steel plate culverts at shallow depth are often designed and constructed with the consideration of the minimum depth of soil cover according to the design standards, which was made in order to minimize any deformation. Additionally, if under unfavorable conditions, slabs are set up for stress relaxation to disperse and minimize the weight of loads transferred to the corrugated steel plate culverts. Nevertheless, if the underground corrugated steel plate culverts are built in areas where the minimum depth of soil cover inevitably cannot be secured, there may occur some deformation. In this paper, a research was carried out to identify the characteristics of deformation in areas where the minimum depth of soil cover is not secured. The result shows that there existed the deterioration of pavement and in its smoothness around the corners of slabs for stress relaxation. To this end, this paper studied the structural stability of the underground corrugated steel plate culverts established in the areas with no minimum depth of soil cover secured, with the consideration of causes and solutions of pavement deterioration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5939-5946
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• 2013

The bridge approach slabs (BAS) to provide a transitional roadway between a roadway pavement and a bridge structure have not performed adequately due to various factors. The current Korean Roadway Design Guidelines treat the BAS as a simply supported beam with 70% of the span length and do not consider settlement and void development underneath the slab. To investigate the effect of soil settlements on the bending moment of BAS, a beam on elastic support (BAS-ES) was used in the present study. The parameters used in this study were span length, washout length, washout location, and soil modulus. It was shown from the parametric study that washout regions closer to the midspan exhibit maximum moment in the slab. Since voids under the BAS have typically been observed to be closer to bridge abutments, the springs from the abutment were removed to simulate settlement and void development in the model. The design moments based on AASHTO LRFD Bridge Design Specifications were compared to those of Korean Standard Specifications for Highway Bridge and Design Trucks for Highway Bridges. Even if the design moment from BAS-ES was used to incorporate the effect of the potential washout, significant savings could still be achieved compared to the current BAS design.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.239-249
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• 2011

The behavior of the fiber reinforced concrete (FRC) base under environmental loads was analyzed numerically as a fundamental study to develop a high structural and functional performance composite pavement system in which the base was formed using FRC and the asphalt or cement concrete surface was placed on it. A two-dimensional finite element model of the FRC base was developed and the sensitivity study was performed with the variables including slab thickness of base, thermal expansion coefficient, elastic modulus, and tensile and compressive strengths. The crack spacing and crack width were selected as representatives of the base behavior. The effects of the selected variables on the crack spacing and crack width were analyzed and the sensitive variables were determined. The results of this study could be useful to determine the optimal material properties of the FRC base for combining well with the surface materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.95-104
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• 2006

The presence of cavitations under pavements or behind tunnel linings of concrete is likely to result in collapse. One method of detecting such voids by non-destructive means is low frequency type radar(GPR). By the way, the size and thickness of small cavitation can't be detected by the present radar technology with low frequency and low resolution when it apply to civil structures like that. To overcome these problems and limitations, this study aims to develope and propose a new analysis method for estimating the depth, cross-sectional size and thickness of cavitations using low frequency radar. A new proposed method is based on the experiments that are carried out for analyzing the correlation between the measurement values(the amplitudes of radar return) of low frequency radar and various type of cavitations. In this process, the threshold value for radar image processing which aims to represent only cavitations to be fitted size can be obtained. As the results, it is clarified that a proposed method has a possibility of estimating cavitation depth, size and thickness with good accuracy in laboratory scale.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.8-14
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• 2021

Post-tensioned prestressed concrete members experience immediate prestress losses as well as time-dependent prestress losses such as creep, dry shrinkage and relaxation. In addition, the stress of the upper and lower parts of the member changes due to the change in dead load due to the replacement of the upper slab and/or pavement. Such changes in fiber stress may affect the safety of the member, and it is necessary to adjust the prestressing force. Therefore, in this study, a screw type of re-tensioning post-tension kit is proposed, and it is verified that the safety against load and the stability against strain are satisfied through the load transfer test specified in EAD160004 and KCI-PS101.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.37-44
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• 2023

In this study, the performance of the support modular system, as substructure of the proposed sustainable-perpetual modular road system to reduce road construction time and maintenance costs was evaluated. A modular road system consisting of 4 support modular cross-beams with a lower curved surface was constructed on the test-bed. Six load cells and eight LVDTs were installed in the center part of two cross-beam support modular systems. Two loads, 50kN and 100kN, were applied to 15 points on the pavement slab to measure the load and displacement occurring in the modular road system. The measured displacements were less than 1 mm, so it is considered that there was no problem in the stability of the actual road. When comparing the two applied loads and the measured loads in the field test, it was considered that the load transmitted to the ground under the support modular system is very small. It is considered that the modular road system with the support modular system is applicable to the actual road site.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.185-191
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• 2010

Because the concrete crack that is the reason of the serviceability and durability degradation of concrete structure can be arisen from either the stress magnitude and gradient or other structural and material defects, the crack strength of concrete is hard to accurately evaluate. Especially, stress-state in concrete plate components such as rigid pavement and long span slab is biaxial flexure stress, and the flexural strength of those component may be different than the traditional rupture modulus of concrete subjected to uniaxial stress. In this study, an experimental investigation to assess of mechanical behavior under uniaxial and biaxial flexure stress is conducted and the proposed optimum specimen configuration is adopted. From the test, the modulus of rupture under uniaxial and biaxial stress are decreased as the size of aggregate or specimen is larger. And biaxial flexure strength of concrete specimens is varied from 39.5 to 99.2% as compared with that of uniaxial strength, and the biaxial strength of specimen with 20mm aggregate size is only 76% of uniaxial strength.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.27-35
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• 2004

Most of concrete fatigue tests currently used are flexural tension or compression methods to investigate the tensile or compressive properties, respectively. However, the concrete pavement or concrete slab is actually subjected to a combined stress condition such as biaxial or triaxial. The split tension test may result in similar stress condition to biaxial stress condition. The purposes of this study were to evaluate the split tension fatigue test method for application in concrete. These were done by a finite element analysis and experimental series. The results were as follows: The optimum configuration of split tension fatigue test was a cylinder of 15cm in diameter and 7.5cm in thickness, which had a little different thickness compared to the KS standard cylinder of ${\phi}15{\times}30cm$. The concrete stress ratio of compressive against horizontal from FEA was 3.1, while that from theory was 3.0. The stress distributions of mortar and steel were almost similar at different thicknesses. The measured static split tensile strengths of concrete and mortar were quite similar at 30cm and 7.5cm thickness cylinders. The measured stress-strain relationship showed their consistency at all specimens regardless of thickness, and confirmed the results from FEA. As a results, the concrete split tension specimen, cylinder of 15cm in diameter and 7.5cm in thickness, could be used at fatigue test because of its accuracy, simplicity and convenience.