• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.11-22
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• 1999

In this study, the validity of the currently used seismic regulations for seismic isolated building structures is investigated, and a new formula for vertical distribution of seismic load is proposed. The distribution formula in UBC-91 did not provide sufficient safety, and thus revised in 1994. However it is pointed out that the revised formula overestimates the seismic load because of its similarity to that of the fixed-base structure. Therefore, in the proposed approach, it is intended to satisfy safety, economy, and applicability by combining the mode shapes of the seismic isolated structure idealized as two degrees of freedom system and those of fixed-base structure. For verification of the proposed formula, both a moment resisting frame and a shear wall system are analyzed. The results obtained from the proposed method turn out to be close to the results from a dynamic analysis.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.53-61
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• 2016

Unburned Carbon(UBC) and NOx emissions from High-moisture coal and Dried coal were investigated in Drop Tube Furnace(DTF). When the same amount of the High-moisture coal and Dried coal were oxidized in DTF, the results show that UBC and NOx emissions of Dried coal case is higher than High-moisture coal case. As the moisture in coal decreases from 40% to 10%, the average gas temperature increases but the moisture concentration in DTF decreases. As the wall temperature increases from $900^{\circ}C$ to $1500^{\circ}C$, the UBC decreases and NOx emissions increases. Especially, the difference for UBC between High-moisture coal and Dried coal decreases with increasing wall temperature.

• Computational Structural Engineering
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• v.8 no.3
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• pp.113-122
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• 1995

The purpose of this study is to evaluate performance and safety of structures designed according to current seismic code or provisions (e.g., Uniform Building Code(UBC), NEHRP provisions, etc.) during lifetime of structures. The performance is represented in terns of reliability in this paper. To perform reliability analyses, a large number of time history response analyses for a given structure are usually required. In this study, to perform reliability analyses ground motions are generated based on nonstationary random process and structures are designed based on UBC. In this paper, responses of structures under a given earthquake is evaluated using dynamic nonlinear time history analyses and also an equivalent nonlinear system (ENS) with response scaling factors. The ENS system is described in the companion paper. Therefore, this paper evaluates the seismic performance of structures and also verify the accuracy of ENS.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.23-32
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• 2004

The local geologic and dynamic site characteristics, which include soil profiles, shear wave velocity profiles and depths to the bed rock were gathered from 148 sites all over the Korean peninsula and those values are compared to those in the western USA. Site response analyses were performed based on equivalent linear scheme using design rock-outcrop acceleration of 0.154g which corresponds to the collapse level of earthquake for seismic category I structure. The results show that the amplification factor based on Korean seismic design guideline underestimates the motion in short-period range and overestimates the motion in mid-period range. It is suggested that the existing Korean seismic guideline based on UBC is required to be modified considering dynamic site characteristics in Korea for the reliable estimation of site amplification.

• Structural Engineering and Mechanics
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• v.23 no.5
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• pp.543-562
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• 2006

Base isolation technology has been accepted as a feasible and attractive way in improving seismic resistance of structures. The seismic design of new seismically isolated structures is mainly governed by the Uniform Building Code (UBC-97) published by the International Conference of Building Officials. In the UBC code, the distribution formula of the inertial (or lateral) forces leads to an inverted triangular shape in the vertical direction. It has been found to be too conservative for most isolated structures through experimental, computational and real earthquake examinations. In this paper, four simple and reasonable design formulae, based on the first mode of the base-isolated structures, for the lateral force distribution on isolated structures have been validated by a multiple-bay three-story base-isolated steel structure tested on the shaking table. Moreover, to obtain more accurate results for base-isolated structures in which higher mode contributions are more likely expected during earthquakes, another four inertial force distribution formulae are also proposed to include higher mode effects. Besides the experimental verification through shaking table tests, the vertical distributions of peak accelerations computed by the proposed design formulae are in good agreement with the recorded floor accelerations of the USC University Hospital during the Northridge earthquake.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.1
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• pp.31-37
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• 2016

Co-firing of biomass with coal is a promising combustion technology in a coal-fired power plant. However, it still requires verifications to apply co-firing in an actual boiler. In this study, data from the Thermogravimetric analyzer(TGA) and Drop tube furnace(DTF) were used to obtain the combustion characteristics of biomass when co-firing with coal. The combustion characteristics were verified using experimental results including reactivity from the TGA and Unburned carbon(UBC) data from the DTF. The experiment also analyzed with the variation of the biomass blending ratio and biomass particle size. It was determined that increasing the biomass blending ratio resulted in incomplete chemical reactions due to insufficient oxygen levels because of the rapid initial combustion characteristics of the biomass. Thus, the optimum blending condition of the biomass based on the results of this study was found to be 5 while oxygen enrichment reduced the increase of UBC that occurred during combustion of blended biomass and coal.

• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.98.2-98.2
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• 2004

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.167-175
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• 2000

Seismic analyses of structures can`t be performed without considering the effect of soil-structure interaction and seismic responses of a structure taking into account the stiffnesses of a foundation-soil system show a significant difference from those with a rigid base. However, current seismic analyses of apartment building structures were carried out assuming a rigid base and ignoring the characteristics of a foundation and the properties of the underlying soil. In this study, seismic analyses of apartment buildings of a particular wall-slab structural type were carried out comparing seismic response spectra of a flexible base with those of a rigid base and UBC-97. Wall-slab type low-rise or mid-height apartment buildings built on the deep soil layer showed a rigid body motion with the reduced seismic responses due to the base isolation effect, indicating that it is too safe but uneconomical to utilize the design spectra of UBC-97 for the seismic analysis of a wall-slab type apartment buildings due to the too conservative design.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1751-1755
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• 2004

Increasing environmental pressures to reduce NOx emission are being placed on coal-fired boilers. To meet the environmental requirements, Doosan Heavy Industries & Construction Co., Ltd.(Doosan) has developed low NOx pulverized coal burner. Low NOx pulverized coal burner has already delivered, and it's combustion performance was evaluated to the NOx and Unburned Carbon(UBC) during the commissioning tests. The test results are shown that the strong relationship is existed between NOx and OFA flow rate, and also fuel-N fraction of coal has effected on NOx emission.

• Journal of the Korean Society of Combustion
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• v.11 no.4
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• pp.22-26
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• 2006

To meet the environmental requirements, Doosan Heavy Industries & Construction Co., Ltd. (Doosan) had developed low NOx pulverized coal burner and it was applied to boiler retrofit project, 130 ton/hr coal fired cogeneration boiler, in 2003. NOx emissionand unburned carbon (UBC) in fly ash were measured during the commissioning tests. In this paper, the operation results of low NOx pulverized coal burner installed in 130 ton/hr coal fired boiler are presented. Burners emitted 160 ppm (@6 % $O_2$ basis) NOx and 3 % UBC with Chinacoal containing 0.86 % fuel nitrogen. And also it was shown that NOx emission rate of low NOx pulverized coal burner is linearly increased with fuel-nitrogen fraction of coal.