• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.147-153
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• 2019

The prestressing steel wire, which is applied a tension to reinforce the structure, is applied flexure simultaneously by the duct and the deviator. In order to evaluate the deflected tensile performance of the prestressing steel wire subjected to both tensile and flexural stresses, the numerical analysis for 600 cases with variables of wire diameters, mandrel diameters, and friction coefficient between mandrel and steel wire was performed. As the result of analysis, the larger the diameter of the steel wire was, the lower the deflected tensile performance was, and the effect decreased with the increase of the wire elongation. The effect of mandrel diameter and friction coefficient between mandrel and wire on the deflected tensile performance of the wire was very small. But the deflected tensile performance and the friction coefficient between mandrel and strand showed a relatively high correlation. Therefore, it is necessary to make enough large elongation to secure the deflected tensile performance. If there is a restriction on the elongation, it is necessary to reduce the diameter of the steel wire to an appropriate value, and to increase the friction between steel wires by adjusting the surface condition of the steel wire.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.1
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• pp.16-21
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• 2014

In the study, tensile, compression and in-plane tests about longitudinal direction of glass fiber were performed. Also, to obtain the material properties of GFRP fabric composite, tensile test was performed. All test were performed by the test method of ASTM. Maximum compressive strength was smaller than the maximum tensile strength at the longitudinal direction test results. Elastic modulus of the tensile and compressive was almost similar at the compression test results in the longitudinal direction. Based on the GFRP fabric composite test results, GF91 was showed good performance at maximum compressive, maximum strain and elastic modulus.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.190-194
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• 2003

Two different types of nondestructive evaluation (NDE) techniques were employed to investigate the tensile behavior of ceramic matrix composites (CMCs). Two NDE methods, ultrasonic testing (UT) and infrared (IR) thermography, were used to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UTC-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.

• Computers and Concrete
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• v.6 no.2
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• pp.155-165
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• 2009

Splitting tensile strength (STS) of high-performance concrete (HPC) is one of the important mechanical properties for structural design. This property is related to compressive strength (CS), water/binder (W/B) ratio and concrete age. This paper presents a clustering-based fuzzy model for the prediction of STS based on the CS and (W/B) at a fixed age (28 days). The data driven fuzzy model consists of three main steps: fuzzy clustering, inference system, and prediction. The system can be analyzed directly by the model from measured data. The performance evaluations showed that the fuzzy model is more accurate than the other prediction models concerned.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.222-225
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• 2006

Pull-off test is widely used to evaluate bond performance between concrete and FRP composite. However, reliability of experiment result declines due to many difference between test methods of each national standards. This study analyzed problems of various existing test methods for pull-off test and suggested standardized test method. In addition, since tensile strength of concrete is smaller than bond strength of epoxy resin, maximum bond strength of epoxy resin shall be limited within tensile strength of concrete. Alternative testing method, therefore, which decrease FRP adhesion areas than concrete adhesion areas is suggested to widen test range of bond strength in pull-off test. In the experimental results, bond performance can be estimated up to two times of tensile strength of concrete by reducing FRP adhesion areas by 1/3.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.195-200
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• 2003

An expert system for estimation of fatigue properties from simple tensile data of material is developed, considering nearly all important estimation methods proposed so far, i.e., 7 estimation methods. The expert system is developed using an expert system shell, UNIK, and the knowledge base is constructed with production rules and frames. Forward chaining is employed as a reasoning method. The expert system has three major functions including the function to update the knowledge base. The performance of the expert system is tested using the 54 ${\sigma}-N$ curves consisting of 381 ${\sigma}-N$ data points obtained for 22 materials. It is found that the expert system developed has excellent performance especially for steel materials, and reasonably good for titanium alloys.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.39-44
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• 2004

A heat and room temperature construction method of asphalt have been mainly applying to rooftop waterproofing in concrete structure, and the rest construction method are sheet, membrane and mortar waterproofing construction method. In particular, joint method in sheet waterproof method is as overlap joint which on being reinforced with fiber and tape, have been applying for job site to mechanical fix using protection disk and anchorage and metal ironwork on the end of sheet. These construction method cause cutting off joint of sheet as behavior of structure according to repairs of sheet itself and thermal conduct, outdoor air environment. In conclusion, we analyzed and examined the application of various sheets and piece ashes about superior 'I' joint which divide from one and the other sheet and progressed about joint construction method of fixing method for overlap.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.103-104
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• 2018

Recently, in addition to greening of roof and artificial soil, Rootproofing to prevent damage to the waterproof layer and structures by roots is recognized as an important task. Therefore, various related products and construction methods have been developed and applied in the field. However, in the case of synthetic polymer-based sheets most commonly used in domestic construction sites, Most are produced using 100% new materials that are not suitable for green trends such as resource conservation and environmental protection. Therefore, in this study, we developed TPO sheet using recycled material, which is a technology that can secure eco-friendliness by utilizing recycled resources. As a result of the evaluation of tensile performance of the TPO sheet according to the recycled material content, The tensile strength of the specimens with the recycled content of 50 ~ 70% was the highest, The elongation rate of the specimen with the recycled content of 30 ~ 40% was the best.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.171-174
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• 2009

This study analyzes the change of the basic characteristics of pavement concrete according to the reinforcement of macro-fiber and the results of the study can be summarized as follows. In the case of the compressive strength of the concrete, the fiber reinforced pavement concrete shows a small decreasing level compared to the basic mixing of pavement concrete (hereafter referred as 'Plain') based on the aging of 28 days. In particular, the polypropylene fiber made in Korea represents a decrease in the strength about 12% compared with that of the Plain. In the case of the tensile strength, it shows certain improvements in the tensile performance compared with that of the Plain. In particular, in the case of the polyvinyl alcohol fiber that shows the largest improvement in tensile performance, it shows an increase in its strength about 21%. In the case of the bending strength, there are no improvements in its strength in the fiber reinforced concrete compared to that of the Plain.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.441-444
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• 2004

This paper presnets the tensile behavior of 8 high performance fiber-reinforced cementitious composites (HPFRCCs) members, each reinforced with one deformed bar 16mm in diameter. The variables included HPFRCC(Ductal, steel cord and polyethylene hybrid fiber, PE fiber) versus normal concrete. Fibers used in HPFRCC significantly increased tensile strength, ductility, and tension stiffening of cementitious materials. For HPFRCC, after first cracking, tensile load continue to rise without fracture localization. Sequentially developed parallel cracks contributed to the inelastic strain at increasing stress level. After yielding of the reinforcing bars, HPFRCC showed increases in loads with increasing strains.