• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.247-258
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• 2008

In this study, static loading tests were performed on H-beam specimens to assess the static behavior of H-beam prestressed with multi-stepwise thermal prestressing method (TPSM). The amount of induced thermal prestress and connection type were differentiated among the 400-mm-high and 6,000-mm-long H-beam specimens to evaluate their effect on the behavior of the beams. From the experimental results, it between the H-beam and the cover-plate increased in yielding load by 13~18%, whereas stiffness increased by 27~34%. In case of specimens with both bolting and welding connection, yie lding load increased by 18~29% and stiffness increased by 43~51%. Multi-stepwise initial stress distribution was also observed from the prestressed specimens, verifying the effectiveness of the multi-stepwise TPSM. By application of the multi-stepwise TPSM, a significant increase in yielding load and stiffness can be achieved, hence increasing sectional and prestressing efficiencies.

• Composites Research
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• v.30 no.1
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• pp.65-70
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• 2017

Carbon fiber reinforced composites have light weight and high mechanical properties. These materials are only applicable in limited shape structure cause by complex curing process and low drapability. To solve this problem, Long Fiber Prepreg Sheet (LFPS) has been proposed. In this research, electric device cover plate was selected and designed by using LFPS. Before the design process, we analyzed the target structure to which the rib structures were applied. And 8-inch tablet PC product was selected. For FE analysis, simple loading and boundary conditions were applied. Stiffness of rib structure was investigated according to the rib pattern and shape changes. Rib pattern and shape were selected based on fixed volume condition analysis results. And uneven rib width model was selected for the best case whose deflection was reduced 6~10% than uniform rib model.

• Steel and Composite Structures
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• v.20 no.1
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• pp.167-184
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• 2016

This paper presents the details of Finite Element (FE) analysis carried out to determine the limiting deformation capacity and failure mode of Laced Steel-Concrete Composite (LSCC) beam, which was proposed and experimentally studied by the authors earlier (Anandavalli et al. 2012). The present study attains significance due to the fact that LSCC beam is found to possess very high deformation capacity at which range, the conventional laboratory experiments are not capable to perform. FE model combining solid, shell and link elements is adopted for modeling the beam geometry and compatible nonlinear material models are employed in the analysis. Besides these, an interface model is also included to appropriately account for the interaction between concrete and steel elements. As the study aims to quantify the limiting deformation capacity and failure mode of the beam, a suitable damage model is made use of in the analysis. The FE model and results of nonlinear static analysis are validated by comparing with the load-deformation response available from experiment. After validation, the analysis is continued to establish the limiting deformation capacity of the beam, which is assumed to synchronise with tensile strain in bottom cover plate reaching the corresponding ultimate value. The results so found indicate about $20^{\circ}$ support rotation for LSCC beam with $45^{\circ}$ lacing. Results of parametric study indicate that the limiting capacity of the LSCC beam is more influenced by the lacing angle and thickness of the cover plate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.91-100
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• 2008

Multi-stepwise Thermal Prestressing Method(TPSM) is a newly proposed prestressing method, which is combined the external prestressing method and the external bonding method. Multi-stepwise thermal prestressing force is induced by cooling process of cover-plate in the multi-stepwise temperature distribution after the cover-plate being bolted to the girder. In this study, the heating capacity test of the developed heating system for applying the multi-stepwise TPSM effectively and multi-stepwise TPSM inducing test of H-beam is performed. Also, a field test of the rhamen type temporary bridge is carried out to evaluate the effect and application of the multi-stepwise TPSM. Truck load was loaded and compared with the structure analysis results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.4 s.56
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• pp.159-169
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• 2009

In this study, static loading tests and numerical analyses of the composite beam strengthened by multi-stepwise thermal prestressing method were carried out to evaluate the prestressing effect of the thermal prestressing prestress and the sectional effect of the installed cover-plate on the increase in the load-carrying capacity of composit beam. From this study, the strengthening method using multi-stepwise thermal prestressing method (TPSM) can be applied to reduce the deflection of the composite beam as well as to strengthening the composite beam by inducing the prestress in case of the occurrence in the large deflection by the insufficiency of the section properties of the composite beam. because of the expectation of the increase in the yield load and the sectional properties of the composite beam.

• Journal of Korean Society of Steel Construction
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• v.12 no.5 s.48
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• pp.463-473
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• 2000

This paper presents the results of the experimental and analytical investigation for the fatigue strength of welded details frequently used in steel bridges, especially for the details with relatively lower fatigue strength. The welded details included four kinds of welded details corresponding to the categories C, D, E and E' which represent the flange attachment details, web attachment details, transverse stiffeners and cover-plate details. Tensile fatigue tests were performed. The test results were compared with other available test results and the fatigue criteria of AASHTO, JSSC and Eurocode specifications. Generally, our test results were well agreed with other test results and satisfied with above-mentioned fatigue design provisions. However, it was found that transversely loaded weld-details showed lower fatigue strength than longitudinally loaded weld-details in transverse stiffener detail, and the test results of those details were not satisfied with AASHTO fatigue provisions. Examining the effect of length of gusset plate attachment details, welded details with longer attachment showed relatively lower fatigue strength, especially for the out-of-plane gusset plate details. It is recommended to perform additional fatigue tests with various loading and detail parameters and to establish the more detailed fatigue categories such as Eurocode or JSSC

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.5-12
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• 2002

This paper presents the results of plate load test and dynamic load test performed to evaluate the performance of geocell which is used to reinforce soft subgrade for high-speed railroad. Efficiency of geocell was observed in the increase in bearing capacity of subgrade and in the reduction of thickness of reinforced sub-ballast. One layer of geocell underlying a 10 cm thick cover soil led to an increase in bearing capacity three to four times larger than that of a crushed stone layer of the same thickness substituted for the geocell and cover soil layer Given the test conditions, the thickness of reinforced sub-ballast can be reduced by approximately 35 cm with the presence of geocell.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1274-1278
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• 2009

Fracture characteristics for plate and dome shapes of glass filled ceramics using shock tube were carried out. Glass filled ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role as separated membrane between combustion and external air, and needs the frangible characteristics that the particles of fractured glass filled ceramics should not affect the internal components of combustion. The objectives of this study are to evaluate the fracture pressures for various thicknesses and diameters of shock impact area. Also fracture phenomena of separated membrane using a shock tube compare with analytical method. The experimental apparatus consists of a driver, a driven section and a dump tank. The used material is glass filled ceramic made from Corning company. Specimens have the thickness of 3, 4.5 and 6mm. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1487-1506
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• 2009

A long-term field experiment of the selected stabilization methods(Cover system, full range and upper range treatment) was conducted to reduce the heavy metal mobility in farmland soil which was contaminated by heavy metals around abandoned mine site. Field experiments were established on the contaminated farmland with the wooden plate and filled with treated soil, which was mixed with lime stone and steel reforming slag except on control plot. Soil samples were collected and analyzed during the experiment period(about 4 months) after the installation of the plots. Field demonstration experiments results showed that the cover system and the full range treatment of the selected stabilization methods applied to the application ratio of lime stone 5% and steel refining slag 2% were effective for immobilizing heavy metal components in contaminated farmland soil.

• Advances in Energy Research
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• v.3 no.3
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• pp.157-165
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• 2015

This research investigates the effect of natural dust accumulation on the glass cover of solar thermal energy conversion systems. Four similar, locally manufactured, flat plate solar collectors are used. All collectors are South oriented with tilt angle of $40^{\circ}$. The glass cover of one collector is kept clean of dust during the experimental period while the second collector is cleaned at the beginning of each month. The third collector is cleaned every two months while the fourth collector is kept un-cleaned throughout the experimental period of four months. The calculated parameters are the solar heat gain rates and the corresponding values of the thermal efficiency. The result of the present work indicates that the percentage of fractional reduction of the useful heat gain rate due to dust accumulation during a period of one and two months is 11.4% and 17.0%, respectively. The percentage decrease of thermal efficiency during the same duration periods is 4.0% and 6.1%, respectively. The percentage of fractional reduction of the useful heat gain rate due to dust accumulation during a period of three and four months is 27.8% and 31.9%, respectively. The percentage decrease of monthly thermal efficiency during the same duration period is 10.2% and 11.3%, respectively.