• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.249-260
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• 2014

When a train enters the tunnel at high speed, the pressure wave occurs. When this pressure wave reaches at the exit of tunnel, some are either emitted to the outside or reflected in tunnel by the form of expansion wave. The wave emitted to the outside forms the impulsive pressure wave. This wave is called 'Micro Pressure Wave'. The micro pressure wave generates noise and vibration around a exit portal of tunnel. When it becomes worse, it causes anxiety for residents and damage to windows. Thus, it requires a counterplan and prediction about the micro pressure wave for high speed railway construction. In this paper, the effects of train head nose and tunnel portal shape were investigated by model test, measurement for the micro pressure wave at the operating tunnel as well as numerical analysis for the gradient of pressure wave in the tunnel. As results, a method for predicting the intensity of the micro pressure wave is suggested and then the intensity of the micro pressure wave is analyzed by the tunnel length and the cross-sectional area.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.562-568
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• 2017

A precast floating slab track with a 5m slab panel and installed with isolators is proposed to solve the noise and vibration problem at existing elevated railway stations. Thus, the construction can be carried out rapidly without interrupting the train operation. However, dynamic instability problems may be caused by repeated discontinuities in track due to the short slab panel length and excessive rail displacement due to the inherent operation mechanism of a floating system in reducing the vibration. Furthermore, the difference of the supporting stiffness at the transition between the floating track and ballast track may raise problems. In this study, the assessment factors to evaluate the dynamic stability of the precast floating slab track are presented and assessed with the vehicle-track interaction analysis. Through the analysis, all values relevant to the stability at the floating track section are found to be acceptable, and the slab panels at the transition section are designed to satisfy the stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.755-760
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• 2016

The demand for independent generators using renewable energy has been increasing. Among those independent generators, small wind turbine generators have been actively developed. Permanent magnets are generally used for small wind turbine generators to realize a simple structure and small volume. On the other hand, cogging torque is included due to the structure of the permanent magnet synchronous machine, which can be the source of noise and vibration. The cogging torque can be varied by the shape of the permanent magnet and core, and it can be reduced using the appropriate design techniques. This paper proposes a design technique that can reduce the cogging torque by changing the shape of the permanent magnets for SPMSM (Surface Permanent Magnet Synchronous Motor), which is used widely for small wind turbine generators. Evolution Strategy, which is one of non-deterministic optimization techniques, was adopted to find the optimal shape of the permanent magnets that can reduce the cogging torque. The angle and outer diameter of permanent magnet were set as the design variable. A 300W class wind turbine generator, whose pole/slot combination was 8 poles/18 slots, was designed with the proposed design technique. The properties of the generator, including the cogging torque and output voltage, were calculated. The calculation results showed that the cogging torque of the optimized model was reduced compared to that of the initial model. The design technique proposed by this paper can be an effective measure to reduce the cogging torque.

• Resources Recycling
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• v.18 no.5
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• pp.63-71
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• 2009

Recyclable wastes coming into material recovery facilities(MRFs) is mostly packed by plastic bag or sack bag. Bag rupturing device is essential to improve capacity and efficiency of MRFs. Bag opening works of MRFs is mostly done by numerous workers and shredder-type bag rupturing device. It often makes a problems; decreased capacity, shredded recyclables, worker safety by explosion and broken glasses, etc. In the present work, bag rupturing device with octagonal rotating blade drums has been developed to solve the existing problems and environment assessment is also performed during operation of the device. Capacity of the device was about 5.6 ton/hr at 8.2 rpm of drum revolution speed and 1.25 m/min of belt conveyor speed. It satisfied initial designed capacity(5.0 ton/hr) and max. capacity 8.8 ton/hr was achieved at 12.5 rpm of drum revolution speed and 1.50m/min of belt conveyor speed. Bag rupturing efficiencies on outer and inner bag were obtained at 100% and about 95.6% as average, respectively and original form of glass bottles in the bag was maintained without broken by about 96.5%. This result shows that the safety in hand sorting by the workers could be improved. As result of environmental assessment on the noise, vibration and particulates, the measured levels on noise, vibration and particulates show the below standard regulatory limits. It could be concluded that the problems of existing devices in MRFs could be solved by adopting the bag rupturing device with octagonal rotating blade drums in on-site operation.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.38-38
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• 2011

일반적으로 레일마모는 열차의 주행안전 및 승차감에 미치는 영향이 크고, 소음 진동의 주요원인으로 작용한다. 또한 레일마모가 발생할 경우 궤도구조의 파괴를 촉진시킴으로써 차량 및 궤도유지보수비를 크게 증가시킨다. 따라서 구간 특성 및 환경 영향 인자 등 현장에서 발생하는 마모 원인을 체계적으로 분석함으로써 마모를 저감할 수 있도록 차량운행 조건과 선로선형 및 궤도구조를 설계하는 것은 중요한 과제이다. CART(Classification And Regression Tree; 분류와 회귀나무) 분석은 패키지화된 좋은 분류 및 예측도구 기법으로 나무의 상위 분리수준에서 일반적으로 나타나는 가장 중요한 입력변수들을 사용하는 등의 입력변수를 선정하는 경우 매우 유용하다. 본 연구에서는 다변수 구간특성 및 환경인자를 고려한 검측 자료 상관관계 분석을 위한 회귀 나무기반 모델(TBM: Tree Based Model) 분석 수행을 위해 지하철 2호선 마모 데이터와 마모 데이터에 영향을 미치는 각종 다변수 구간특성 및 환경인자를 사용하였다. 2호선 지하철의 구간특성 인자 및 환경인자는 레일의 종류, 레일의 위치, 도상, 곡률반경, 캔트 슬랙 및 운행 일수 등으로 구분하였다. 레일의 종류는 ks-50kg과 ks-60kg 두 종류의 레일이 있으며, 레일의 위치는 지상과 지하로 크게 구분할 수 있다. 도상은 콘크리트 도상, 자갈 도상과 일부 구간의 방진상 콘크리트 도상으로 구분할 수 있으며, 곡률반경은 직선구간과 완화곡선 구간 및 최소 250m부터 627m까지 분포된 원 곡선 구간으로 구분할 수 있다. 캔트 간격은 최소 96cm 부터 120cm 간격으로 구분하며, 슬랙은 5~9cm에 분포하고, 운행 기간은 해당 기간 동안 유지보수 이력이 없는 구간을 선정하여 2005년부터 2006년까지 4번에 걸쳐 검측된 지하철 2호선 내선 마모데이터를 사용하였다. 총 X1부터 X7까지 총 7개의 구간특성 또는 환경특성을 영향인자로 선정하였으며, 이러한 영향인자에 의해 결정되는 종속 인자로 Y1인 직마모와 Y2인 측마모를 선정하여 이 중 실질적으로 지하철 궤도의 성능 평가에 주요 판단인자로 사용되는 측마모와 구간특성 및 환경영향인자와의 상관관계 분석을 수행하였다. 해당 마모 데이터가 검측되는 기간 동안 유지보수 이력이 없는 12272 point의 데이터를 검출하였고 CART 프로그램을 이용하여 데이터를 분석하였으며, CART 프로그램의 해석을 위해 종속변수인 직마모량은 각 검측 지점의 마모량에 해당하는 등급으로 변환하여 분석을 수행하였다. 레일의 마모에 영향을 미치는 구간특성 및 환경인자와 종속 변수로 사용된 레일의 마모량 사이의 CART를 이용한 상관관계 분석은 실제 구조물에서 영향인자간의 상관 관계와 유사하며, 추후 연구에서는 이를 바탕으로 하여 정량화된 검측 데이터를 종속변수로 하여 구간특성 또는 환경인자 등 외부 영향인자를 고려한 궤도 검측데이터와의 상관관계 분석을 수행할 계획이다.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.53-63
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• 2013

Bored pre-cast piles using PHC piles is widely used in foundation of building structures constructed in urban areas because noise and vibration due to pile installation are low. However, since slime is formed at the base of borehole and the density of bearing stratum surrounding the base of borehole is decreased due to stress relaxation in drilling process of bored pre-cast pile method, the base load capacity of bored pre-cast piles is very low compared to the strength of bearing stratum. In this study, a new type of PHC pile, which short steel pipe with the same diameter as the PHC pile is attached to the pile tip, is developed to increase the base load capacity of bored pre-cast piles. In order to check the effect of the use of new PHC pile on the base load capacity of bored pre-cast piles, field pile load tests are performed for bored pre-cast piles using the new and existing PHC piles. Results of the pile load tests show that the new PHC pile gives higher base load capacity to bored pre-cast piles than the existing PHC pile, since the tip of new PHC pile is penetrated to undisturbed bearing stratum passing through the slime at the base of borehole and the loosened bearing stratum under the slime by pile driving using light hammer.

• Journal of the Korean GEO-environmental Society
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• v.21 no.6
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• pp.19-25
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• 2020

In the recent downtown works, there are frequent cases where the work on existing piles is impossible due to the influence from lack of space and surrounding environment. In such cases, there has been growing cases of using the micropile method that is available to work with the small equipment and asserts the bearing capacity of the existing piles. The micropile method is a type of drilled shaft with the diameter of a pile to be around 75 mm~300 mm that, even for a case where it has certain surrounding structure, foundation and spatial obstacle, there is almost no work difficulty and the work is feasible under all types of soil conditions. In addition, the work can be done in places where the ceiling of the building is low with less vibration and noise in the work process that such method is significantly used for foundation reinforcement of existing buildings. With respect to the motion characteristics that are changed depending on the foundational characteristics or when the micropile is applied with compression or tensile force, there is very few studies conducted. Therefore, under this study, through the data analysis of the field loading test regarding the micropile worked in the fields, it clarifies the settlement and characteristics of bearing capacity following the embedded condition of the ingredients and piles that consist the foundation if the compression and tensile force are applied to the micropile, and by facilitating the statistical analysis program, SAS, to carry out the analysis on the main elements influencing on settlement of the micropile and bearing capacity.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.519-527
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• 2016

The demand of construction risk analysis is rapidly increased to improve the competitiveness of construction companies and the sound management of the construction project. However, estimating the amount and uncertainty of the risk is difficult due to the wide range of risks in the construction industry. Moreover, most of the research on risk management of construction risk is only focused on the causes of risk without separate the internal and external risk. This study statistically analysis the internal risk and external risk based on the accidents cases which are caused at construction sites to define the difference and importances of the risk. An accident cause analysis and T-test analysis are carried out to reach the goal of study. The results of the study are expected to be used as a guideline of construction project risk analysis.

• Korean Journal of Construction Engineering and Management
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• v.6 no.5 s.27
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• pp.186-192
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• 2005

The purpose of this study is to find the reality of environmental management cost in construction projects and to suggest some policies in order that owners appropriate the environmental management cost reasonably in the construction budget for reducing the environmental pollution at job sites. We surveyed the actual state of appropriating and expending the environmental management cost over 122 construction sites. According to the results of the survey, while the appropriated rate of the environmental management cost was 0.59% of the total construction cost. the expended rate reached at 0.94%. When examining the antipollution facilities which were operated in job sites, the investment for equipment against air-pollution such as tire washer, dust-proof device was relatively higher than other antipollution equipment. As the method appropriating the environmental management cost, we concluded that a quantity-per-unit costing method is more reasonable than appropriating at a fixed rate of total construction cost considering that there is little correlation between total construction cost and the environmental management cost. To do so, antipollution facilities that must be examined at a design or estimation stage of a construction project should be prescribed by the law. Moreover, referenced cost data for the quantity-per-unit costing should be prepared and officially published.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.99-107
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• 2004

This research is to determine the level of environmental pollution at a blasting construction area which is the origin of noise, vibration, and suspended particle, and to compare the results with other domestic and international standard data. This experiment is also to find out the effects resulting from blasting construction and to propose a plan that can decrease environmental pollution. The blasting construction area is a factory site which is about one and half million square meter and sewage disposal plant is about ninety thousand square meter. Both were selected as the areas for the tests to be conducted in determination test. The test to determine the level of noise, vibration, and total suspended particle was conducted thirty times around the blasting construction area by comparing measurement results and numerical analysis. However, as the test was not conducted in the laboratory but in the actual blasting construction area, it was not possible to do the test with the same exact conditions each true. Therefore, the test was not ideal as conditions could change from test to test. For the most part, the level of noise was below the standard level of 70dB. Every vibration test was under the standard limitation. For example, a house, 200m away was tested for noise and vibration and the level was found to be under the 0.2 cm/sec which is the standard for specialty designed cultural sites., i.e very low level. Also a buried oil pipeline that was 30m away also marked under 2.0cm/sec which is the norm for an industrial area. However, if there were an oil pipeline under the house, the amount of charging gunpowder per hole should be decreased compared to the amount used in the test. The test result for suspended particles under the standard limitation which is 24hour average 300$\mu\textrm{g}$/㎥ at a distance from blasting wavelength, but at detonator, total suspended particle from the blast origin exceeded the standard limitation. If explosion occurs when it detonates in the hole, most of the energy would be absorbed in the crushing of rocks, but some remaining energy would make noises and vibration inevitable. So the important thing is how to minimize the environmental pollution from the blasting. There should be regulations in order that the standard limitation is not exceeded, and to decrease the environmental pollution from the blasting.