• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.901-907
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• 2013

In this study, flexural strength properties of concrete under biaxial stress state were experimentally investigated. Tests for size effect and fatigue behaviour of concrete under biaxial stress were carried out by the ASTM C 1550 and the biaxial flexure test(BFT). The results given by the biaxial tests were compared to those by the third-point bending test. Test results showed that biaxial flexural strengths obtained from the ASTM C 1550 and the biaxial flexure test are greater than the strength by the third-point bending test. As the size increases, the uniaxial and biaxial flexural strength decreases. However, the slope of the size effect of the biaxial strength was greater than that of the uniaxial strength. Finally, the fatigue response of concrete under the biaxial stress state was similar with that for uniaxial stress state.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.337-345
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• 2006

In this study, to evaluate fatigue characteristics of developed composite bridge deck, compression fatigue test at girder support and flexural fatigue test for the 2.8m-long flexural test model were carried out. For the test specimen, DB 24 truck load was applied up to 2,000,000 cycles. In the compression fatigue test, behavior at deck tube and its bonded connection were evaluated. In the flexural fatigue test, deck behavior at mid-span and girder connection were evaluated.

• Advanced Composite Materials
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• v.17 no.3
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• pp.215-224
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• 2008

The present study aims to design a multilayer microstrip antenna with composite sandwich construction and investigate fatigue behavior of this multilayer SAS (surface antenna structure) that was asymmetric sandwich structure for the next generation of structural surface technology. This term, SAS, indicates that the structural surface becomes an antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, antenna elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.2 GHz. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of the SAS was obtained. The experimental results of bending fatigue were compared with single load level fatigue life prediction equations and in good agreement. The SAS concept is can be extended to give a useful guide for manufacturers of structural body panels as well as antenna designers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1647-1650
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was 16${\times}$8 array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue lift curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.108-111
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16\;{\times}\;8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.4
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• pp.482-505
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• 1993

The purpose of this study was to evaluate the fracture characteristics and the effect of resin bonding of laminate porcelain. In order to characterize the indentation-induced crack, Young's moduli and characteristic indentation dimensions were measured. The fatigue life under three point flexure test was measured using the electro-dynamic type fatigue machine, and the crack propagation with thermocycling was investigated on the condition of 15 second dwell time each in $5^{\circ}C\;and\;55^{\circ}C$ bath. The Vickers indentation pattern and the fracture surface were examined by an optical microscope and a scanning electron microscope (SEM). The results obtained were summarized as follows ; 1. Young's moduli(E) of the laminate porcelain and the resin cement used in this experiment were $62.56{\pm}3.79GPa$ and $15.01{\pm}0.12GPa$, respectively. 2. The initial crack size of the laminate porcelain was $69.19{\pm}5.94{\mu}m$ when an indentation load of 9.8N was applied, and the fracture toughness was $1.065{\pm}0.156MPa\;m^{1/2}$. 3. The fatigue life of laminate porcelain showed the constant fracture range at the stress level 27.46-35.30MPa. 4. When a cyclic flexure load was applied, the fatigue life of resin-bonded laminate porcelain was more decreased than that of laminate porcelain. 5. When a thermocycling was conducted, the crack growth rate of resin-bonded laminate porcelain was more increased than that of laminate porcelain. 6. Fracture surface showed the radial crack, the lateral crack, and the macroscopic crack branching region beneath the plastic deformation region when an indentation load of 9.8N was applied.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.1
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• pp.54-64
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• 2007

This study is a fundamental research in order to establish the design code of recycled aggregate concrete structure. The structural properties of recycled aggregate concrete such as flexure, shear, fatigue, compression, and bond development are experimentally investigated and confirmed. In this study, laboratory-scale reinforced concrete beam, column, and pull-out test specimens using recycled coarse aggregate are manufactured. Then, the structural performances of recycled aggregate concrete according to replacement ratios of recycled coarse aggregate are evaluated. Also, finite element analysis using commercial code DIANA is carried out to predict the test results and the analysis results are compared with test results in this study. Structural test results showed that the structural performances of recycled aggregate concrete specimens with 60% replacement ratio are reduced by approximately 15-20%. These results indicated that the replacement ratio of recycled coarse aggregate within 30% is a suitable to use for structural members. The results of finite element analysis showed that the specimens with 30% replacement ratio possessed similar or more excellent structural performance than normal concrete specimens. However, recycled aggregate concrete with 60% replacement ratio of recycled coarse aggregate must be carefully considered for structural applications due to significant decrease of the failure loads.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.633-638
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• 1997

This study was performed to investigate the fatigue behaviour and fatigue damage process of RC structures under repeated load. Especially, the behavior of RC beams subjected to flexure-shear force has been focused. The test results show that the deflections of beam and the strains of longitudinal steels and stirrups under cyclic loads increase with constant rate, and these increases depend on diagonal crack openings and strain increases. The present study provides useful data for the analysis of damage accumulation of reinforced concrete beams under repeated loadings.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.483-486
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• 2005

The polymer concrete is drawing a strong interest as high-performance materials in the construction industry. Resins using recycled PET offer the possibility of a lower source cost of materials for making useful polymer concrete products. Also the recycling of PET in polymer concrete would help solve some of the solid waste problems posed by plastics and save energy. Polymer concrete beams using unsaturated polyester resins based on recycled polyethylene terephthalate (PET) plastic waste were used in our study for grasping its structural behavior of static and fatigue. As a result of static test, Compression stress distribution of Polymer concrete indicates linear behavior such as triangles. Although polymer concrete is high strength materials, its ductility capacity is excellent. From the fatigue test results, There was almost no difference on flexural characteristics between before and after fatigue loading. Therefore, recycled PET polymer concrete remains excellent structural ability after fatigue loading.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.781-792
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• 1997

This study was peformed to evaluate the dynamic fatigue characteristics of the dental ceramics for all-ceramic crown. A feldspathic porcelain of VMK68. glass ceramic of IPS-Empress, and glass infiltrated alumina ceramic of In-Ceram were used. Disc specimens were prepared to the final dimensions of 12 mm in diameter and 1 mm in thickness. The biaxial flexure test was conducted using a ball-on-three-ball method. 240 specimens were tested in $37^{\circ}C$ water by testing 20 samples at each of four loading rates:0.05, 0.2, 1, and 5mm/min. 60 specimens were tested in a moisture-free environment by testing 20 samples at 5mm/min. The inert strength of VMK68 was 80.25MPa, and the fatigue parameters were n=29.1, ${\sigma}_{fo}=52.90MPa$. The inert strength of IPS-Empress was 104.76MPa, and the fatigue parameters were n=32.46, ${\sigma}_{fo}=67.52MPa$. The inert strength of In-Ceram was 429.33MPa, and the fatigue parameters were n=31.46, ${\sigma}_{fo}=258.36MPa$. 10-year failure stresses of VMK68, IPS-Empress, and In-Ceram were 20.3MPa, 24.8MPa, and 93.6MPa, respectively. Failure strength and fatigue life showed the highest value in In-Ceram, and then, IPS-Empress and VMK68.