• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.66-71
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• 2013

Soft bending pipe is widely used for freezing equipment and shipbuilding. These pipe have some problems that they cause occasionally outside wrinkle, crack, wall thinning phenomena. However, vending machines which have been made to solve the problems completely, are not yet. In this study, to settle these problems, we proved the effectiveness of the self-made mandrel by results of simulation as the basic for the development of precision high-quality vending machine ; presents the solution method of the wall thinning phenomena by analyzing circular deformation and damage of bending pipe.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.2
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• pp.47-56
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• 2015

At the present, the mechanized form roads pavement was constructed with plain concrete. Mostly, it was used by welded wire mesh for preventing crack. Cellulose fibers for the reinforcement of concrete offer relatively high levels of elastic modulus, fiber count (per unit weight), specific surface, and bond strength to cement-based materials. The construction of concrete pavement confirmed that cellulose fiber reinforced concrete was applicable to mechanized form roads pavement. In the study, cellulose fibers were used here at 0.08 % volume fraction, which is equivalent to a fiber content of $1.2kg/m^3$. Cellulose fiber reinforced concrete were compared with plain concrete. Field test results indicated that cellulose fiber reinforced concrete showed slightly to increase of 28 days compressive strength and improved the initial strength. it tended to increase of splitting tensile strength. Test results showed that the slump and air content tend to decreased. but, the variation of air contends is very little. Also, construction cost of cellulose fiber reinforced concrete is less than about 25.7 % the case of welded wire mesh previously used. Therefore, The cost reduction is expected to be possible in construction site by mechanized form roads pavement.

• Architectural research
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• v.7 no.1
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• pp.49-54
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• 2005

Conventional studies have focused on the reduction in the water-cement ratio, the use of various admixtures, etc., to ensure the durability of reinforced concrete structures against such deterioration factors as carbonation and chloride attack. However, improvement in the concrete quality alone is not considered sufficient or realistic for meeting the recent demand for a service life of over 100 years. This study intends to improve the durability of reinforced concrete structures by improvement in the reinforcing steel, which has remained untouched due to cost problems, through subtle adjustment of the steel components to keep the cost low. As a fundamental study on the performance of Cr-bearing rebars in steel reinforced concrete structures exposed to corrosive environments, The test specimens were made by installing 8 types of rebars in concretes with a chloride ion content of 0.3, 0.6, 1.2, 2.4 and $24kg/m^3$. Corrosion accelerated curing were then conducted with them. The corrosion resistance of Cr-bearing rebars was examined by measuring crack widths, half-cell potential, corrosion area and weight loss after 155 cycles of corrosion-accelerating curing. The results of the study showed that the corrosion resistance increased as the Cr content increased regardless of the content of chloride ions, and that the Cr-bearing rebars with a Cr content of 5% and 9% showed high corrosion resistance in concretes with a chloride ion content of 1.2 and $2.4kg/m^3$, respectively.

• Structural Engineering and Mechanics
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• v.12 no.1
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• pp.1-16
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• 2001

A reliable and accurate method has been developed to predict the flexural deformation response of structural concrete members subject to service load. The method that has been developed relates the extent of concrete cracking, measured as a function of the magnitude of applied moment in a member, to the reduction in the effective moment of inertia of cracked reinforced concrete members under service load conditions. The ratio of the area of the moment diagram where the moment exceeds the cracking moment, to the total area of the moment diagram for any loading, provides the basis for the calculation of the effective moment of inertia. This ratio also represents mathematically a probability of crack occurrence. Verification of this method for the determination of the effective moment of inertia has been achieved from an experimental test program, and has included beam tests with different loading configurations, and shear wall tests subjected to a range of vertical and lateral load levels. Further verification of this method has been made with reference to the experimental investigation of other recently published work.

• Earthquakes and Structures
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• v.3 no.1
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• pp.37-57
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• 2012

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

• Journal of Korean Society of Steel Construction
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• v.15 no.4 s.65
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• pp.403-412
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• 2003

The composite metal deck plate system has been widely used for office structures. Recently, however, the flat deck plate has been developed to apply the composite slab system to residential structures. Reduction in construction cost and time can be expected by using expanded metal instead of wire mesh as crack control reinforcements. This study proposed a composite slab system composed of a new-shaped steel deck plate and expanded metal. Twelve specimens were tested to evaluate the structural performance of the new composite slab system. The test results were summarized mainly in terms of maximum load carrying capacity and failure behaviors of each specimen.

• Journal of the Korean housing association
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• v.17 no.1
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• pp.97-105
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• 2006

The purposes of this study are to find out the current status and features of earth housing, and to explore users' level of satisfaction and needs of improvement about earth housing. Primary findings are as follows: (1) The area of earth housing is generally 25-34 pyong and the construction cost of earth housing is usually 3,000,000-3,400,000 won per pyong. (2) The age of earth house users is generally forties, fifties, and sixties. And their occupation is usually retiree and farmer. The age of earth based pension users is generally twenties and thirties. (3) The construction method of earth housing is usually earth brick structure reinforced with wood structure and earth brick structure(adobe). (4) The finish of outer wall is generally earth brick laying and earth plaster. And the finish of inner wall is usually wall paper and earth plaster. Roof tile and asphalt shingle is frequently observed as roof finish. (5) Users' satisfaction about earth housing is investigated high level. Especially, the satisfaction degrees about faculty of humidity control, stink elimination, prevention from sick house syndrome, support for psychological stabilization and deep sleep are observed very highly. (6) Reduction of construction cost and prevention of crack is investigated as needs of improvement about earth housing.

• Steel and Composite Structures
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• v.28 no.6
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• pp.767-778
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• 2018

The purpose of this study is to investigate how a fully restrained bolted beam splice affects the connection behavior as a column-tree connection in steel special moment frames under cyclic loading when located within the plastic hinge zone. The impacts of this attachment in protected zone are observed by using nonlinear finite element analyses. This type of splice connection is designed as slip-critical connection and thereby, the possible effects of slippage of the bolts due to a possible loss of pretension in the bolts are also investigated. The 3D models with solid elements that have been developed includes three types of connections which are the connection having fully restrained beam splice located in the plastic hinge location, the connection having fully restrained beam splice located out of the plastic hinge and the connection without beam splice. All connection models satisfied the requirement for the special moment frame connections providing sufficient flexural resistance, determined at column face stated in AISC 341-16. In the connection model having fully restrained beam splice located in the plastic hinge, due to the pretension loss in the bolts, the friction force on the contact surfaces is exceeded, resulting in a relative slip. The reduction in the energy dissipation capacity of the connection is observed to be insignificant. The possibility of the crack occurrence around the bolt holes closest to the column face is found to be higher for the splice connection within the protected zone.

• Progress in Superconductivity and Cryogenics
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• v.22 no.1
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• pp.1-6
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• 2020

This is a parameter study for the direct fabrication of a large grain YBCO bulk superconductors using Y₂O₃, BaCO₃ and CuO powders without any grinding step. The cracks, which have been formed due to volume contraction during calcination step, have been prevented by controlling the heating rate at 930~950 ℃. It has been observed that multi-grain growth has occurred due to the dissolution of Sm123 seed due to the retention of carbon in Ba-Cu-O melt. In order to accelerate the carbon release in prior calcination heat treatment, the reduction of pellet thickness and the drilling of artificial holes have been applied. Single-grain YBCO bulk superconductor has been successfully fabricated by stacking multiple thin slab. However, the crack formation has been rather prominent for the compact with artificial holes. The use of buffer pellet, which is supposed to act as diffusion barrier, has prevented the dissolution of Sm123 seed crystal and has led to the growth of single grain of high content of carbon containing specimen.

• Advances in concrete construction
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• v.2 no.4
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• pp.309-324
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• 2014

In the design of reinforced concrete structural walls, in order to ensure adequate inelastic displacement behaviour and to sustain deformation demands imposed by strong ground motions, special reinforcement is considered while designing. However, these would lead to severe reinforcement congestion and difficulties during construction. Addition of randomly distributed discrete fibres in concrete improves the flexural behaviour of structural elements because of its enhanced tensile properties and this leads to reduction in congestion. This paper deals with effect of addition of steel fibres on the behavior of high performance fibre reinforced cement concrete (HPFRCC) slender structural walls with the different volume fractions of steel fibres. The specimens were subjected to quasi static lateral reverse cyclic loading until failure. The high performance concrete (HPC) used was obtained based on the guidelines given in ACI 211.1 which was further modified by prof.Aitcin (1998). The volume fraction of the fibres used in this study varied from 0 to 1% with an increment of 0.5%. The results were analysed critically and appraised. The study indicates that the addition of steel fibres in the HPC structural walls enhances the first crack load, strength, initial stiffness and energy dissipation capacity.