• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.181-193
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• 2015

High-frequency staircases are widely used nowadays to meet aesthetics and functionality needed in modern architecture. Unfortunately, no design guide is available in domestic practice to predict response or evaluate the vibration performance of high-frequency staircases. SCI-P354 published by the Steel Construction Institute of UK provides the formula for effective impulsive force. However, this formula was shown to overestimate the response of high-frequency staircases excited by fast ascending and descending over 2.2Hz pace frequency because it was developed based on the walking test in a slow pace frequency. This study proposes a semi-analytical formula to predict the response of stiff staircases based on analytical and experimental studies of response acceleration for various walking frequencies covering 1.4~4.5Hz.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.549-556
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• 2002

The natural frequency of a system is commonly used in evaluating the serviceability condition of a floor. However. the current equations recommended in many building codes do not consider the various material types of a slab system; thus. different results are observed. Likewise. the transformation of a slab section required to predict the natural frequency of a composite deck plate is complicated. due to the varying shapes of the deck plates. Therefore. a new and simplified method of transforming a composite slab into an equivalent concrete slab is proposed. he modified vibration prediction equation was proposed based on the current vibration prediction equation recommended by LRFD. Compared to other equations. it is the closest to those obtained from experiments. The modified equation provides about 14.3% more accurate results than that recommended by LRFD. Likewise. the applicability of the proposed equation to other types of composite deck plate floor system was validated.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.731-740
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• 2008

This paper deals with the fatigue behavior and strength of a new-type of steel-concrete composite bridge deck. The new-type composite bridge deck consists of corrugated steel plate, welded T-beams, stud-type shear connectors and reinforced concrete filler. A total of eight composite bridge deck specimens were fabricated, the fatigue tests were conducted under four-point bending test with three different stress ranges in constant amplitude. According to the test results, the fatigue crack generated at the welding part of the corrugated steel plate, progressed down to the bottom of the steel plate and encountered the crack, which came out from the opposite side at the same position. After the two cracks were connected at the bottom of the steel plate, the lower flange was cut off and the fatigue crack developed up to the T-beam. And the displacements and strains of fatigue test specimens were increasing with cyclic loading number, these were changed sharply at the fatigue failure. The fatigue results are compared with the design S-N curves specified in the Korea Highway Bridge Design Specifications and data in NCHRP 102 and NCHRP 147 report. The new-type composite bridge deck has a stress category of C, which means that new-type composite bridge deck can be designed by the current fatigue design specifications provided for steel members.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.6 s.40
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• pp.55-66
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• 2004

Recently, many high-rise apartment buildings using the box system, composed of only reinforced concrete walls and slabs, have been constructed. In residential buildings such as apartments, vibrations occur from various sources and these vibrations transfer to neighboring residential units through walls and slabs. It is necessary to use a refined finite element model for an accurate vibration analysis of shear wall building structures. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. Therefore, an efficient analytical method, which has only translational DOFs perpendicular to walls or slabs by the matrix condensation technique, is proposed in this study to obtain accurate results in significantly reduced computational time. If all of the DOFs except those perpendicular to walls or slabs in the shear wall structure eliminated using the matrix condensation technique at a time, the computational time for the matrix condensation would be significant. Thus, the modeling technique using super elements and substructuring technique is proposed to reduce the computational time for the matrix condensation. Dynamic analysis of 3-story and 5-story shear wall example structures were performed to verify the efficiency and accuracy of the proposed method. It was confirmed that the proposed method can provide the results with outstanding accuracy requiring significantly reduced computational time and memory.

• Journal of Korean Society of Steel Construction
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• v.26 no.5
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• pp.385-396
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• 2014

Traditionally, domestic steel design and construction practice has provided extra shear studs to moment frame beams even when they are designed as non-composite beams. In the 1994 Northridge earthquake, connection damage initiated from the beam bottom flange side was prevalent. The upward moving of the neutral axis due to the composite action between steel beam and floor deck was speculated to be one of the critical causes. In this study, full-scale seismic testing was conducted to investigate the side effects of the composite action in steel seismic moment frames. The specimen PN700-C, designed following the domestic connection and floor deck details, exhibited significant upward shift of the neutral axis under sagging (or positive) moment, thus producing high strain demand on the bottom flange, and showed a poor seismic performance because of brittle fracture of the beam bottom flange at 3% story drift. The specimen DB700-C, designed by using RBS connection and with the details of minimized floor composite action, exhibited superior seismic performance, without experiencing any fracture or concrete crushing, almost identical to the bare steel counterpart (specimen DB700-NC). The results of this study clearly indicate that the beams and connections in seismic steel moment frames should be constructed to minimize the composite action of a floor deck if possible.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.94-99
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• 2021

It was found that mixing patterns suddenly changed at an impeller rotation speed in a dished bottom vessel with dual Rushton turbines. Two isolated mixing regions like doughnuts rings generated at a low rotational speed and three isolated mixing regions generated at a higher speed. This phenomenon was observed at the mixing condition in transition area, where the power number with baffle was the same as that without baffle. We found a phenomenon in which the flow state in a dish-bottom agitation tank equipped with a two-stage Rushton turbine blade changes at a certain rotational speed. In the laminar flow region, the isolated stable donut rings were formed even when the rotational speed was changed, and no specific variation in the mixing pattern was observed. In the transition region, the two isolated thick unmixed donut rings do not change even if the rotation speed is changed in the flat bottom vessel, whereas in the dished bottom vessel, when the rotation speed is 450 rpm, the two isolated thick unmixed donut rings are changed to three isolated thin donut rings and then improved mixing. In the dished bottom vessel, in the range of Re=138~178, the isolated ring-shaped unmixed region appeared in three places and the size was also large. But in the flat bottom vessel, the isolated thick ring-shaped unmixed region appeared in two places in Re=116~176 and the size was also small. It appeared in two places, and the size was also small. The condition in which this phenomenon is observed is a transition region, and it was found that when the baffle plate is attached, the power number starts to increase compared to when the baffle plate is not present. In addition, when the mixing Reynolds number exceeded 300 and a slight turbulence was mixed in the flow state, the disconnection of these flow pattern was resolved and the mixture was completely mixed.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.132-138
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• 2011

Inducing the natural lighting into building has been commonly applied to the spaces where artistic objects are displayed to create better visual environment for the appreciation. The direct natural lighting, especially through top lighting system may, however, bring forth discoloing of highly light-sensitive materials such as paintings or demanding additional cooling load. In addition, it causes to create glare against appreciators or to yield in visual distraction due to the extreme contrast on the inner surfaces of the spaces. Shading device such as louver is capable of preventing such voidable cases with careful manipulation. This study aims to provide basic design guide-line when the flat-form louver has to be applied to top lighting system. Interaction between the daylight and louver was simulated by Reluxpro program with variation of the attachment location, the angle of the lover, surface reflectivity, to obtain the illumination of the floor surface. This study yields the louver just under the top lighting window with 90 degree angle gives the most desirable way of employment when the uniform illumination on the floor surface is required.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.333-345
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• 2008

concrete deck bridges are increasingly aplied to twin- girder bridges and open-stel box girder bridges.One of the most dificult isues in the design of shear conect ors is the mater of achieving ful composite action. Many connectors in smal area require a significant section los of precast decks resulting in difficult reinforcement details. In this closer spacing than the required minimum spacing in the design codes was evaluated through static tests. Test results s howed that the ultimate strength decreased as the conector spacing was reduced. The strength enhancement was observed due to aditional reinforcement for precast slabs or for shear pockets. Thus, the design of group stud shear connection needs to anticipate failure modes and the conector failure should be induced. Based on the test results, an empirical equation consi dering stud spacing was proposed to evaluate the ultimate strength of group stud shear conection. Fatigue tests showed n o reduction in fatigue life of the group stud shear conection in the range of this research. Details of the precast decks wer e enhanced using the findings of the study.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.519-528
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• 2008

A simple steel-concrete composite deck is developed for preventing the lateral torsional buckling of girders that are under construction and for reducing the term of works using H-shaped rolled beams as bridge girders. A new type of shear connectors is also developed for the composite behavior between a simple steel-concrete composite deck and the rolled beams by the connecting conditions between the deck and the girders. One is a connector bolt that is lengthened and split or tightened with two nuts and the other is an I-shaped rolled beam welded on a steel plate with a number of holes punched through the web. In this study, to estimate the shear strength of those shear connectors the push-out tests are performed and the test results are compared with that of the previous studies and the codes. The result of the push-out tests of the connector bolts showed that the shear performance is similar to that of the stud connector and revealed that the equation for the shear strength in the Korean Specification of Highway Bridge overestimates the shear capacity of the connector bolt whose diameter is larger than 19mm. From the push-out tests of punched I-shaped rolled beams with varying welding amounts, with the small amount of welding, shear capacity is governed by the shear capacity of welding. On the other hand, shear capacity is governed by the size of the punched I-shaped rolled beams, regardless of the amount of welding.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1997.10a
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• pp.90-94
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• 1997

조석파가 연안해역에 접근하게 되면 바닥마찰이나 수심의 감소에 따른 조위의 비선형 효과 및 육지와의 경계부분에서 발생하는 흐름의 곡률 등 여러 가지 요인에 의해 파의 진행에 변화가 야기되며 (Pugh,1987), 이에 따라 동일 천문조의 간섭에 의해 나타나는 overtide, 또는 2개 이상의 천문조간 상호 간섭에 의해 나타나는 compound tide와 같은 천해조가 발생하게 된다. (중략)