• Journal of the Korea Institute of Building Construction
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• v.8 no.3
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• pp.75-83
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• 2008

In this paper, concrete material tests were carried out to investigate influence of steel fiber volumn ratios on variations of workability and strength characteristics of steel fiber reinforced high-strength concrete, $50MPa{\sim}90MPa$ of compressive strength, according to increase of fiber volume. Test specimens were arranged with six levels of concrete compressive strength and fiber volumn ratios, 0.0%, 0.5%, 1.0%, 1.5%, 2.0%. The test results showed that steel fiber reinforced high-strength concrete($70MPa{\sim}90MPa$, 1.5% fiber volumn ratio) with good workability of slump 20cm could be used practically and effects of steel fiber reinforcement in improvement of concrete strength and toughness characteristics such as splitting tensile strength, flexural strength, and diagonal tensioned shear strength, were more distinguished in high-strength concrete than general strength concrete. And the test results indicated that splitting tensile strength of fiber reinforced concrete was proportioned to the product of steel fiber volumn ratios, $V_f(%)$ and sqare root of compressive strength, $\sqrt{f_{ck}}$, and the increasing rate was in contrast with that of flexural strength, and increase of diagonal tensioned shear strength was remarkable at steel fiber volumn ratio, 0.5%.

• Clean Technology
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• v.2 no.2
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• pp.100-125
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• 1996

After recycle of spent materials has been optimised, there remains a proportion of waste which must be dealt with in the most environmentally friendly manner available. For materials such as municipal waste, clinical waste, toxic waste and special wastes such as tyres, incineration is often the most appropriate technology. The study of incineration must take a process system approach covering the following aspects: ${\bullet}$ Collection and blending of waste, ${\bullet}$ The two stage combustion process, ${\bullet}$ Quenching, scrubbing and polishing of the flue gases, ${\bullet}$ Dispersion of the flue gases and disposal of any solid or liquid effluent. The design of furnaces for the burning of a bed of material is being hampered by lack of an accurate mathematical model of the process and some semi-empirical correlations have to be used at present. The prediction of the incinerator gas phase flow is in a more advanced stage of development using computational fluid dynamics (CFD) analysis, although further validation data is still required. Unfortunately, it is not possible to scale down many aspects of waste incineration and tests on full scale incinerators are essencial. Thanks to a close relationship between SUWIC and Sheffield Heat&Power Ltd., an extended research programme has been carried out ar the Bernard Road Incinerator plant in Sheffield. This plant consists of two Municipal(35 MW) and two Clinical (5MW) Waste Incinerators which provide district heating for a large part of city. The heat is distributed as hot water to commercial, domestic ( >5000 dwelling) and industrial buildings through 30km of 14" pipes plus a smaller pipe distribution system. To improve the economics, a 6 MW generator is now being added to the system.

• Advanced Composite Materials
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• v.17 no.1
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• pp.57-73
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• 2008

The present paper focuses on experimental verification of the ply-by-ply basis inelastic analysis of multidirectional laminates. First of all, rate dependence of the tensile behavior of balanced symmetric cross-ply T800H/epoxy laminates with a $[0/90]_{3S}$ lay-up under off-axis loading conditions at $100^{\circ}C$ is examined. Uniaxial tension tests are performed on plain coupon specimens with various fiber orientations $[{\theta}/(90-{\theta})]_{3S}$ ($\theta$ = 0, 5, 15, 45 and $90^{\circ}C$) at two different strain rates (1.0 and 0.01%/min). The off-axis stress.strain curves exhibit marked nonlinearity for all the off-axis fiber orientations except for the on-axis fiber orientations $\theta$ = 0 and $90^{\circ}$, regardless of the strain rates. Strain rate has significant influences not only on the off-axis flow stress in the regime of nonlinear response but also on the apparent off-axis elastic modulus in the regime of initial linear response. A macromechanical constitutive model based on a ply viscoplasticity model and the classical laminated plate theory is applied to predictions of the rate-dependent off-axis nonlinear behavior of the cross-ply CFRP laminate. The material constants involved by the ply viscoplasticity model are identified on the basis of the experimental results on the unidirectional laminate of the same carbon/epoxy system. It is demonstrated that good agreements between the predicted and observed results are obtained by taking account of the fiber rotation induced by deformation as well as the rate dependence of the initial Young's moduli.

• Structural Engineering and Mechanics
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• v.52 no.5
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• pp.889-901
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• 2014

Very long life fatigue tests were carried out on 16Mn steel base metal and its welded joint by using the ultrasonic fatigue testing technique. Specimen shapes (round and plate) were considered for both the base metal and welded joint. The results show that the specimens present different S-N curve characteristics in the region of $10^5-10^9$ cycles. The round specimens showed continuously decreasing tendency while plate specimens showed a steep decreasing step and an asymptotic horizontal one. The fatigue strength of round specimen was found higher than plate specimen. The fatigue strength of as-welded joint was 45.0% of the base material for butt joint and 40% for cruciform as-welded joint. It was found that fracture can still occur in butt joint beyond $5{\times}10^6$ cycles. The cruciform joint has a fatigue limit in the very long life fatigue regime ($10^7-10^9$ cycles). Fatigue strength of butt as-welded joint was much higher as compared to cruciform as-welded joint. Improvement in fatigue strength of welded joint was found due to UPT. The observation of fracture surface showed crack mainly initiated from welded toe at fusion areas or geometric discontinuity sites at the surface in butt joint and from welded toe in cruciform joint.

• Coupled systems mechanics
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• v.9 no.2
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• pp.163-182
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• 2020

Coupled thermo-mechanical analysis of reinforced concrete slab at elevated temperatures from a fire accounting for nonlinear thermal parameters is carried out. The main focus of the paper is put on a one-way continuous reinforced concrete slab exposed to fire from the single (bottom) side as the most typical working condition under fire loading. Although contemporary techniques alongside the fire protection measures are in constant development, in most cases it is not possible to avoid the material deterioration particularly nearby the exposed surface from a fire. Thereby the structural fire resistance of reinforced concrete slabs is mostly influenced by a relative distance between reinforcement and the exposed surface. A parametric study with variable concrete cover ranging from 15 mm to 35 mm is performed. As the first part of a one-way coupled thermo-mechanical analysis, transient nonlinear heat transfer analysis is performed by applying the net heat flux on the exposed surface. The solution of proposed heat analysis is obtained at certain time steps of interest by α-method using the explicit Euler time-integration scheme. Spatial discretization is done by the finite element method using a 1D 2-noded truss element with the temperature nodal values as unknowns. The obtained results in terms of temperature field inside the element are compared with available numerical and experimental results. A high level of agreement can be observed, implying the proposed model capable of describing the temperature field during a fire. Accompanying thermal analysis, mechanical analysis is performed in two ways. Firstly, using the guidelines given in Eurocode 2 - Part 1-2 resulting in the fire resistance rating for the aforementioned concrete cover values. The second way is a fully numerical coupled analysis carried out in general-purpose finite element software DIANA FEA. Both approaches indicate structural fire behavior similar to those observed in large-scale fire tests.

• Geomechanics and Engineering
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• v.20 no.3
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• pp.207-220
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• 2020

Clay soils have a big potential to become contaminated with the oil derivatives because they cover a vast area of the earth. The oil derivatives diffusion in the soil lead to soil contamination and changes the physical and mechanical properties of the soil specially clay soils. Soil stabilization by using new material is very important for geotechnical engineers in order to improve the engineering properties of the soil. The main subjects of this research are a- to investigate the effect of the cement and epoxy resin mixtures on the stabilization and on the mechanical parameters as well as the microstructural properties of clay soils contaminated with gasoline and kerosene, b- study on the phenomenon of clay concrete development. Practical engineering indexes such as Unconfined Compressive Strength (UCS), elastic modulus, toughness, elastic and plastic strains are all obtained during the course of experiments and are used to determine the optimum amount of additives (cement and epoxy resin) to reach a practical stabilization method. Microstructural tests were also conducted on the specimens to study the changes in the nature and texture of the soil. Results obtained indicated that by adding epoxy resin to the contaminated soil specimens, the strength and deformational properties are increased from 100 to 1500 times as that of original soils. Further, the UCS of some stabilized specimens reached 40 MPa which exceeded the strength of normal concrete. It is interesting to note that, in contrast to the normal concrete, the strength and deformational properties of such stabilized specimens (including UCS, toughness and strain at failure) are simultaneously increased which further indicate on suitability and applicability of the current stabilization method. It was also observed that increasing cement additive to the soil has negligible effect on the contaminated soils stabilized by epoxy resin. In addition, the epoxy resin showed a very good and satisfactory workability for the weakest and the most sensitive soils contaminated with oil derivatives.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.1033-1040
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• 2011

The premixed burner is a very strong candidate for using household boiler burner system because it has high efficiency, low emission and can be used in compact boiler system. Usually, household boiler burner systems use a Bunsen burner, which consists of an inner rich premixed flame and fuel burned completely by a secondary air supply. It has a relatively long flame length and operates in a high excess of air, so it is difficult to fit such a burner into a high efficiency compact boiler. In this paper, the characteristics of a premixed combustion burner for surface media such as metal fiber, ceramic, and SUS fin were evaluated. In particular, the flow velocity over the burner surface for the cold flow characteristics of the surface material were measured and adjusted. The combustion tests were carried out by taking pictures of the flame and measuring the flame temperature. The amounts of CO and NO were measured and the characteristics of the surface burner materials, combustion chamber, and heat exchangers were evaluated for various excess air ratios and heating values.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1727-1732
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• 2010

Forensic engineering is the area of expertise of people qualified to serve as engineering experts in courts of law or during arbitration proceedings. An aerial-lifter can lift and carry load, including people, using power. Recently, failure of aerial-lifter internal parts while working and sweeping causing injuries and damage to property almost always generates conflict between the automaker and customer. Hence, the investigation of such events generally involves an engineering analysis. One of the possible reasons for accidents, such as a vehicle catching fire is the failure of oil pressure machine and the supporting pin. The results of formal inspections and engineering tests can reveal the cause for the failure of the mechanical parts. Therefore, the failure mechanism is analyzed by adopting fractography methods and by applying an instrumented indentation technique to compare the material properties of the reference part with those of the malfunctioning part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.255-261
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• 2010

Forensic engineering is the area of expertise of those qualified to serve as engineering experts in courts of law or arbitration proceedings. Especially failure of internal parts during vehicle fire accidents causing injuries and damage to property almost always generates conflict between the automaker and customer. Hence, the investigation of such events generally involves an engineering analysis. One of the possible reasons for such accidents caused by vehicle fire is the failure of the piston and connecting rod. By formal inspections and engineering tests, this study shows the results of investigation and the cause of failure of the mechanical parts. For this purpose the failure mechanism is analyzed by using fractography methods and by applying an instrumented indentation technique to compare the material properties of the reference part with those of the malfunctioning part.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.6
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• pp.247-256
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• 2014

The regulations to reduce energy consumption and carbon dioxide emission in building sectors are being developed and promoted all over the world. However, in Korea, as balcony extension of the apartments has been legally allowed, it became prevalent and resulted in excessive energy consumption. This study derived the possibility of PCM application to the thermal storage wall system through theoretical consideration and investigated the problems occurring when the balcony space has been extended to the diverted space. In addition, this study aims at the possibility of verifying the installation and confirming the cooling energy reduction effect, by conducting measuring tests with the actual installation of PCM applied thermal storage wall system. As a result of theoretical consideration, it is determined that the disadvantages with the existing thermal storage wall system can be complemented by applying PCM, and this study suggests the PCM applied Thermal Storage Wall System. The study was conducted on 1/6 of a miniature inner room of a domestic apartment with 84 $m^2$ of exclusive area. From the results of actual measurements, it is confirmed that the balcony extension structure can gain 11.3% of more calories than the existing balcony structure, resulting in the increase in cooling energy usage. It is determined that the installation of the PCM applied Thermal Storage Wall System may gain 25.2% of less calories to reduce cooling energy usage.