• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.181-192
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• 2007

The purpose of this study is to analyse and compare experimentally flexural behavior of RC beams strengthened with CFRP plates by different methods, and finally suggest the evaluation equations of flexural capacity of RC beams with the aim of application of prestressed CFRP strengthening. The experimental parameters are compressive strength, reinforcement ratio, prestressing level and strengthening methods. The non-prestressed specimens failed on account of separation of the plates from the beams due to premature de-bonding, while most of the prestressed specimens failed due to CFRP plate fracture. The evaluation equations of flexural capacity of RC beams is suggested and these equations have a good reliability in predicting flexural strength of RC beams.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.1-12
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• 2017

In this study, It was purpose to provide preliminary data for extension of the applicability of deep corrugated steel plate composite members by steel grade and shear reinforcement method. From the result of flexural test on deep corrugated plates composite members using GR40 and SS590, positive moment capacity was increased about 28% by SS590 steel. But to change steel grade was proved to have insignificant effects for increasement of negative moment capacity. In the moment test result of same overlapping length, Increasement rate of positive and negative moment capacity was not significantly improved by increasing the number of bolt. It was estimated to be due to the characteristics of bolt connection such as distance between centers of bolts, edge distance of bolt. In the test result on the spacing of shear reinforcement, positive moment capacity was increased and deformation of negative moment was reduced as the distance decrease. In the test result on the shape of shear reinforcement, positive and negative moment resistance was increased about 2% ~ 7% by U shaped shear reinforcement. In conclusion It was estimated that moment capacity of deep corrugated steel plate composite members are depend on steel grade of deep corrugated steel plate, spacing of shear reinforcement and reinforcing bar.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.567-574
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• 2010

As a eco-friendly material, Hwangtoh(red clay) has been studied for a partial or complete replacement of portland cement. Most of existing studies focused on the mechanical properties of the Hwangtoh concrete including the compressive strength, drying shrinkage, creep. In the present study, the flexural capacity of the beams made with the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated Hwangtoh replacing all the cement. The simple beams were tested under two point static loading. The flexural strength, cracking moment, deflection, and ductility were compared with those of the beams made with ordinary portland cement concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.166-175
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• 2009

An experimental study was carried out to estimate the flexural performance of steel fiberreinforced self-compacting concrete. Seven slabs with three different steel fiber-reinforced concretes were prepared to make beam specimens. After proper curing period, each slab was cut to five beams with a diamond saw. The beam specimen was tested with displacement control method to obtain load-deflection curve. As the results, the self-compacting concrete beam showed higher flexural strength, ductility and toughness index compared to the normal concrete beam. This means that steel fiber-reinforced self-compacting concrete can be used more widely in the field of architecture and civil engineering because of its self-compactability and good mechanical properties.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4192-4200
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• 2015

In this paper, dispersibility of steel fiber is improved mixing with form for material development of protection and blast resistant structure sprayed concrete. And it is developed a high toughness cellular sprayed concrete material using steel fiber. Oversupply form for dispersibility improvement of steel fiber is mostly fade away through sprayed, finally it is satisfied with the proper mixing ratio under 3 % ~ 6 %. This is considered for compressive strength and flexural toughness. Test results of compressive strength showed superior strength capability in 28, 56 days, also flexural strength and flexural toughness is great. Then oversupply form is enhanced for dispersibility of steel fiber and I think that it did not cause decreasing of strength. But analysis results of pore structure through image analysis failed for a great spacing factor and specific surface area. This is largely measured in spacing factor because air content have a grate evaporation effect for sprayed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.3
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• pp.43-50
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• 2019

Effects of tensile strength and aspect ratio of steel fiber on compressive and flexural behavior of steel fiber-reinforced concrete (SFRC) with high- and normal-strength were investigated. Also, this study explores compressive behavior of SFRC with different loading rate. For this purpose, four types of steel fiber were used for SFRC with specified compressive strength of 35 and 60 MPa, respectively. Cylindrical specimens with a diameter of 150 mm and height of 300 mm were made for compression test, and prismatic specimens with a $150{\times}150mm$ cross-section and 450 mm span length were made for flexural test. Test results from compression and flexural tests indicated that the toughness of concrete significant increased with steel fibers. Especially, using steel fiber with high tensile strength and aspect ratio can be lead to performance improvement of high-strength SFRC. In this study, equations are suggested to predict compressive toughness ratio of SFRC from flexural toughness ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.49-58
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• 2013

Eight small scale circular reinforced concrete columns were tested under cyclic lateral load with constant axial load. Test specimens were designed with 4.5 aspect ratio. The selected test variables are longitudinal steel ratio, transverse steel ratio, yielding strength of longitudinal steel and axial load ratio. The test results of columns with different longitudinal steel ratio, transverse steel ratio and axial load ratio showed different seismic performance such as equivalent damping ratio, residual displacement and effective stiffness. It was found that the column with low strength of longitudinal steel showed significantly reduced seismic performance, especially for equivalent damping ratio and residual displacement. The regulation of flexural over-strength is adopted by Korea Bridge Design Specifications (Limited state design, 2012). The test results are compared with nominal strength, result of nonlinear moment-curvature analysis and the design specifications such as AASHTO LRFD and Korea Bridge Design Specifications (Limited state design).

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.820-831
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• 2020

Fumigation treatment is mainly used on dead trees affected by the oak wilt disease to prevent the spread of damage. To verify the possibility of intensive use of the damaged Mongolian Oak wood treated by the fumigation treatment, we performed the compression and bending performance evaluation of the fumigation treated wood. The fumigation was done with Nemasect (Metam-sodium) for about 9 months. The dry longitudinal compressive strength of the fumigation treated oak wilt-diseased wood at the ambient temperature and humidity, and the compressive modulus of elasticity were measured to be 58.87MPa, and 5.66GPa, which were similar to the non-treated wood. The strength performance of mature wood of fumigation treated wood was 16% higher than that of juvenile wood. The compression fracture of the non-treated oak wood showed various shapes, however, most of the fumigation treated wood showed shear-type fracture shape. The bending strength of the fumigate treated wood was measured to be 157.43MPa, which was 8% higher than that of the non-treated wood, and the bending modulus of elasticity was measured to be 16.38GPa, which was 16% lower than that of the non-treated wood. However, it was confirmed that the coefficient of variation for the bending strength performance value of the fumigation treated wood was lower than that of the non-treated wood.

• Journal of Korean Society of Steel Construction
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• v.19 no.4
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• pp.357-366
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• 2007

This paper is a pilot study regarding an experimental and parametric study to investigate the structural behavior of slimfloor beam(ASB) in fire. The objective of this research is to obtain the rational fire resistance design method through understanding the structural behavior of composite members in fire. The flexural capacity of slimfloor section under various thermal conditions is examined on a basis of the strength retention of the materials at elevated temperatures and full bonding assumption. The effect of web thickness and ASB depth to the moment capacity in fire is also examined.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.315-323
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• 2010

Five concrete compressive stress-strain models have been analyzed to check the validity of the strength method for determining the nominal moment of strengthened members using commercially available computer language. The results show that the concrete stress-strain models do not influence on the flexural analysis. The moment of a strengthened member obtained from the flexural analysis at concrete compressive strain reaching 0.003 is well agreed with nominal moment using the strength method. The flexural analysis results show that when the steel reinforcement, FRP ratio, FRP failure strain, and concrete failure compressive strain are relatively lower, the strength method overestimates the flexural capacity of the strengthened members.