• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.141-148
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• 2016

This paper employed finite element method (FEM) to study the dynamic response of Steel Fiber-Reinforced Concrete(SFRC) panels subjected to impact loading by spherical projectiles. The material properties and non-linear stress-strain curves of SFRC were obtained by compression test and flexural test. Various parametric studies, such as the effect of fiber volume fraction and thickness of panels, are made and numerical analyses are compared with experiments conducted. It is shown that protective performance of concrete panels will be improved by adding steel fiber. Area loss rates and weight loss rates are decreased with increasing fiber volume fraction. Also, penetration modes can be expected by FEM, showing well agreement with experiment. Results can be applied for designing the protection of military structures and other facilities against high-velocity projectiles.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.253-256
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• 2008

Although researches on the beams strengthened with Fiber reinforced Polymers (FRPs) have recently been conducted around the world, there are few researches on the beams with FRPs under a sustained load. This paper presents the behavior of the beams with Carbon Fiber Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) under a sustained load during 300 days. Strains of steel and FRP reinforcement were measured in order to investigate the behavior of the beams. Additionally, Adjusted Effective Modulus Method (AEMM) and Ghali and Farve's method were used to predict increase in the stress and strain caused by creep and shrinkage. Through the experiment, it was found that the beam with CFRP is more effective than the beam with GFRP in terms of flexural strengthening. Compared with analytical results, it was indicated that strains of tension steels were overestimated, whereas strains of compression steels were underestimated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.3
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• pp.49-56
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• 1989

Recently, a growing attention is paid to the development of new construction materials. The fiber-reinforced concrete is recognized as one of the most promising new construction materials. A comprehensive experimental study was conducted to explore the mechanical behavior of steel fiber reinforced concrete. The major variables in the experiment were the fiber contents and the lengths of steel fibers. The flexural, tensile, and compressive behavior of steel fiber reinforced concrete were investigated. The present study shows that the strength and ductility are remarkably increased with on increase of fiber content. The rate of strength increase due to steel fibers was found to be the highest in tension, the middle in flexure, and the lowest in compression. This indicates that the steel fibers play a major role in increasing the tensile capacity. The present study gives a thorough examination on the mechanical behavior of steel fiber reinforced concrete and allows more realistic use and design of steel fiber reinforced concrete.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.679-690
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• 2011

Since the elastic buckling problem of the plate has been studied both experimentally and theoretically, the buckling loads with various boundary conditions and loads can be easily determined. Currently, flange and web design specifications are based on the buckling stress and the post-buckling strength and include a safety-factor. Therefore, this study extended suchresearch to the linear buckling theory with ideal conditions and to the ultimate state with post-buckling. The current specifications are based on elastic buckling stress; and therefore, further research on the ultimate behavior of the plate is required. The ultimate strength design concept, which allows finite deflection, is used in this studyto maximize the post-buckling strength in a steel box. An empirical equation, which provides the ultimate strength of the steel box due to the change in the slenderness and optimum rigidity, are suggested based on the experiment results. Moreover, the appropriateness of the current design specifications was analyzed and discussed.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.253-260
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• 2010

The purpose of this paper is to investigate the behavior of concrete-filled tube columns for footing connections. Eight specimens were tested to investigate such structural behavior according to the column base type. The specimens consisted of concrete-filled steel tube columns (or bare steel tube columns), reinforced concrete footings, and base plates (or stud connectors). The specimens were subjected to lateral cyclic load. The cyclic load was applied according to a predetermined strength sequence. The results of the experiment indicated that the flexural strength of the stud-connector- type column base is higher than that of the base-plate-type column base. The structural behavior of the concrete-filled tube column base was similar to that of the bare steel column base.

• Journal of the Korea Institute of Building Construction
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• v.20 no.4
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• pp.305-311
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• 2020

Polymer modified cement mortar (PCM) can improve the performance of adhesion strength, flexural strength, chemical resistance, etc., compared with cement mortar, and is widely used when repairing RC structures. However, PCM causes a burst in an environment with high temperature and fire rate, which causes problems in the stability of the structure. In this study, for the purpose of developing explosive reduction PCM, the polymer mixing ratio is 2%, 4%, 6%, the fiber length is 6mm, 12mm, 6+12mm, and the PP fiber mixing rate is 0.05 Vol% and 0.1 Vol%. Furnace heating experiment (600℃, 800℃) was carried out. As a result of comparative analysis of the explosive properties, it was confirmed that the explosive reduction effect due to the fiber incorporation was insufficient when the polymer mixing amount was 6% or more.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.4
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• pp.1130-1147
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• 2014

Large size ships have a very flexible construction resulting in low resonance frequencies of the structural eigen-modes. This feature increases the dynamic response of the structure on short period waves (springing) and on impulsive wave loads (whipping). This dynamic response in its turn increases both the fatigue damage and the ultimate load on the structure; these aspects illustrate the importance of including the dynamic response into the design loads for these ship types. Experiments have been carried out using a segmented scaled model of a container ship in a Seakeeping Basin. This paper describes the development of the model for these experiments; the choice was made to divide the hull into six rigid segments connected with a flexible beam. In order to model the typical feature of the open structure of the containership that the shear center is well below the keel line of the vessel, the beam was built into the model as low as possible. The model was instrumented with accelerometers and rotation rate gyroscopes on each segment, relative wave height meters and pressure gauges in the bow area. The beam was instrumented with strain gauges to measure the internal loads at the position of each of the cuts. Experiments have been carried out in regular waves at different amplitudes for the same wave period and in long crested irregular waves for a matrix of wave heights and periods. The results of the experiments are compared to results of calculations with a linear model based on potential flow theory that includes the effects of the flexural modes. Some of the tests were repeated with additional links between the segments to increase the model rigidity by several orders of magnitude, in order to compare the loads between a rigid and a flexible model.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.2
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• pp.11-16
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• 1980

For vibration analysis of stiffened plates the orthotropic plate analogy is commonly accepted. As to stiffened plates in contact with water, however, there is still much uncertainty in estimation of the added mass because of the lack of direct methods. The authors, considering that for added mass of plates there are many reliable data derived theoretically or experimentally available, suggest a method to estimate the added mass of a stiffened plate by combining the mass increase factor, $\beta$, of an equivalent orthotropic plate and the correction factor, $\kappa$, for the effects of stiffeners. The latter is to be derived from systematic experimental investigations. Then, the natural frequency in water, f', can be calculated from that in air, f, by the equation $f'=f/\sqrt{1+\kappa\beta}$. To investigate practical applicability of this method, a systematic experiment was carried out with five uniaxially stiffened plates. Each of them had a plate of same size, $600mm{\times}600mm{\times}3.2mm$, but stiffeners of different size in the web-depth, 41.6mm, 51.2mm or 66.8mm and of different spacing 75mm, 100mm, or 150mm. Natural frequencies were measured under simply supported-edge conditions in both air and water, and corresponding $\kappa$ values derived. In spite of wide variations of web-depth and spcae of stiffeners, the experimental results show that the diversity of $\kappa$ values is not remarkable; mean values of $\kappa$ are 1.31 with standard deviation of 0.025 for the first modes and 1.27 with that 0.077 for the second modes. Hence, the authors concluded that the above $\kappa$ values can be used generally for the cases of uniaxially stiffened plates both sides of which contact with water, and that $\kappa$ values of general use for the cases of cross-stiffened plates may also be obtainable from similar experiments.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.749-752
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• 2008

This experimental study compared polymer cement mortar with inorganic polymer binder mortar for physical properties by Si/Al mol ratio change of inorganic polymer binder. As the result of this experiment, We found that when Si/Al mol ratio goes up flexural strength and compressive strength increases but workability becomes worse. And according to the keeping them for 28 days we found that physcal property becomes worse when Si/Al mol ratio is larger than 2.61. When Si/Al mol ratio of inorganic polymer binder is from 2.43 to 2.61 compressive strength increases than over 32% after keeping for 7 days and over12 % for 28 days

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.19-26
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• 2020

This study aimed to develop non-sintered cement that could replace portland cement which emits large amount of carbon dioxide during firing process. For this purpose, ground granulated blast furnace slag, type c fly ash and slaked lime were used. In addition, through the experimental results, the characteristics of the non-sintered cement binders according to the mixing ratios will be identified, and the utilization plans for the precast concrete products will be presented. In this experiment, non-sintered cement binders using industrial by-products were prepared to compare the flexural strength and compressive strength of each of the 3, 7 and 28 days. As a result, the results satisfy the KS of the target product proposed in this study. Therefore, this study presents the possibility of using precast concrete products by developing non-sintered cement binders using industrial by-products.