• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.250-253
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• 2000

The fiber orientation in FRP has a great effect on the strength of FRP because the strength of FRP mainly depends on the strength of fiber. Unidirectional FRP made by pultrusion method has comparatively lower compressive strength than tensile strength. Compressive strength of unidirectional FRP may be increased by filament winding layer which has tensile stress when compressive stress was loaded. In this study, compressive strength and stresses of FRP rods were simulated according to the winding orientation of glass fiber. Inner part of FRP was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method. Simulated value and real evaluated compressive strength were compared to investigate stresses which is prominent to the fracture of FRP. The shear stresses had a great effect on the strength of FRP although the stress of parallel direction of FRP was much higher.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.47-50
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• 2009

The existing techniques used to estimate and manage the compressive strength of concrete do not include the environmental factors that influence the development of compressive strength and the compressive strength itself. Thus, it is necessary to develop a reasonable yet simple way to measure the compressive strength of concrete structures at construction sites by considering concrete's mechanical properties and curing environment. This study was conducted to propose an acrylic form and a junction isolation mold with crack-inducing boards that uses non-destructive methods to create and collect concrete test samples that are cured in the same condition as the actual concrete structures. junction isolation molds were used in high-strength and super high-strength concrete to evaluate the reliability of compressive strength evaluation on the test sample. The following were the findings of this study:

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.957-960
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• 2000

The purpose of this study was performed to estimate the influence of compressive strength of the concrete according to change test specimens of concrete were investigated by measurements of slump, air content and compressive strength. As a result, according to moved test specimens, the compressive strength, fiexed test specimens effected on Concrete compressive strength, test specimens than moved test specimens, increased 4∼10% fixed test specimens, 2∼9% moved test specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.675-678
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• 2004

The importance of predicting concrete compressive strength of in concrete structures is gradually increasing in construction industry. The estimation of concrete compressive strength of is a critical factor of the construction schedule and quality control. This study was performed to examine the relationship between concrete compressive strength and stress wave velocity which was determined by the impact echo method and SASW method.

• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.7-24
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• 1986

The purpose of this study was to observe the compressive strength, compressive fatigue strength, surface hardness, water sorption and solubility of eight different posterior restorative composite resins. Eight composite resins were tested for their strength of the compressive and compressive fatigue with prepared two different types of specimens (I and T-type) using a Instron universal testing machine (model No. 1332). The hardness was measured with a Knoop hardness tester (MVH-2, Tokyo) for each cylindrical specimen, 7mm in diameter and 5mm thick. The water sorption and solubility were evaluated with the prepared composite resin disks, 20mm in diameter and 1mm thick. The results were as follows: 1. The compressive strength, compressive fatigue strength and hardness were noticed to be Increased by increasing the volume content of filler. 2. The compressive strength was appeared to be independent on the type of specimen, but the compressive fatigue strength was found to be greatly influenced by the type of specimens. 3. The composite resins having higher compressive strength had also higher compressive fatigue limits. 4. The compressive fatigue limits at $10^5$ stress cycles were about 50-80% of the compressive strength and were showen to be dependent on the materials and type of specimens. 5. The larger the filler particle size was, the lower was the water sorption. And the water sorption of BIS-GMA resin was higher than that of urethane resin. 6. The visible light-cured composite resin had a higher value of solubility than the chemically- cured composite resin. And the solubility tended to decrease by increasing the volume content of filler.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.189-194
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• 2001

In this study, ultimate strength of concrete deep beams with an opening is predicted by using Strut-and-Tie Model with a new effective compressive strength. First crack occurs around an opening by stress concentration due to geometric discontinuity. This results in decreasing ultimate strength of deep beams with an opening compared with general deep beams. With fundamental notion that ultimate strength of deep beam with an opening decreases as a result of reduction in effective compressive strength of a concrete strut, an equivalent effective compressive strength formula is proposed in order to reflect ultimate strength reduction due to an opening located in a concrete strut. An equivalent effective compressive strength formula which can reflect opening size and position is added to a testified algorithm of predicting ultimate strength of concrete deep beams. Therefore, ultimate strength of concrete deep beam with an opening is predicted by using a simple and rational STM algorithm including an equivalent effective compressive strength formula, not by finite element analysis or a former complex Strut-and-Tie Model

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.69-74
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• 2002

The following results are achieved from a mortar flow test depending on stainless steel slag fineness, replacement ratio, and a research on material age compressive strength, strength activity index. 1. Flow is proportional to the stainless steel slag fineness within the limits of 4000~8000$\textrm{cm}^2$/g, but in the case of fineness 20000$\textrm{cm}^2$/g flow decreases at all conditions except the case of replacement ratio 10%. 2. As stainless steel slag replacement ratio increases, Mortar of flow somewhat decreases. 3. As stainless steel slag blends, compressive strength decreases, but in proportion to the increase of age, compressive strength increases. 4. As stainless steel slag replacement ratio, compressive strength decreases. 5. In the case of stainless steel slag fineness 6000$\textrm{cm}^2$/g and 20.000$\textrm{cm}^2$/g, compressive strength of revelation ratio has the maximum value when it's replacement ratio is 10%.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.542-549
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• 2004

The compressive strength of concrete is commonly used criterion in producing concrete. However, the tests on the compressive strength are complicated and time-consuming. More importantly, it is too late to make improvement even if the test result does not satisfy the required strength, since the test is usually performed at the 28th day after the placement of concrete at the construction site. Therefore, accurate and realistic strength estimation before the placement of concrete is being highly required. In this study, the estimation of the compressive strength of concrete was performed by probabilistic neural network (PNN) on the basis of concrete mix proportions. The estimation performance of PNN was improved by considering the correlation between input data and targeted output value. Adaptive probabilistic neural network (APNN) was proposed to automatically calculate the smoothing parameter in the conventional PNN by using the scheme of dynamic decay adjustment algorithm. The conventional PNN and APNN were applied to predict the compressive strength of concrete using actual test data of a concrete company. APNN showed better results than the conventional PNN in predicting the compressive strength of concrete.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.121-130
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• 2000

Currently, in evaluating a flexural strength of a concrete member, the effect of specimen depth has not been systematically studied, even though its effect on ultimate strength of a section is very important. For all types of loading conditions, the trend is that the strength of a member tends to decrease when the member depth increases. In this study, the influence of specimen depth on flexural compressive strength of concrete member was examined experimentally. A series of C-shaped specimens subjected to axial compressive force and bending moment were tested using three geometrically similar specimens with different length-to depth ratios (h/c = 1, 2 and 4) which have compressive strength of 55 MPa. The results indicate that the flexural compressive strength decreased as the specimen depth increased. A model equation was derived based on regression analyses of the experimental data. Also, the results show that ultimate strain decreases as the specimen depth increases. Finally, a general model equation for the depth effect is proposed.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.205-213
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• 2007

Strength relationships are presented through experimental data from the concrete strength tests in this study. Various strength tests such as the compressive, flexural, and splitting tensile strength and the modulus of elasticity are included. An experimental work was performed to determine the various strength characteristics for various mix designs. Three different coarse aggregates such as granite, limestone, sandstone were used and included were fine aggregates such as natural sand, washed sand and crushed sand. Also included was cement amount as experimental variable. It was confirmed that each strength value with respect to curing time is to follow a typical strength development curve. With this somewhat reliable test results various strength relationships such as flexural strength-compressive strength, splitting tensile strength-compressive strength, modulus of elasticity-compressive strength, splitting tensile strength-flexural strength were analyzed through statistics. Experimental data were well fitted to the 0.5-power relationship of flexural strength and compressive strength which has been commonly accepted. The splitting tensile strength is expected to be best in the linear relationship from the flexural strength data. Finally splitting tensile strength was found to be proportional to the 0.87 power of the cylindrical compressive strength.