• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.1-8
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• 1995

One of the most destructive forces around greenhouses is wind. Wind loads can be obtained by multiplying velocity pressure by dimensionless wind force coefficient. Generally, wind force coefficients can be determined by wind tunnel experiments. The wind force coefficient distribution on a single - span arched greenhouse was estimated using experimental data and compared with reported values from various countries. The results obtained are as follows : 1. The coefficients obtained from this study agree with the values proposed by G. L. Nelson except about 0.5 of difference in the middle region of roof section. This discrepancy is mainly attributed to the dissimilarity of experimental conditions (or wind tunnel test such as Reynolds number, type of terrain, surface roughness of model, location of the lapping and measuring methods. 2. Considering that the wind force coefficients are varied along the height of a wall at wind direction perpendicular to wall, structural analysis using subdivided wind force coefficient distribution is more resonable for wall. 3. It is recommendable that wind force coefficient distribution on a roof should take more subdivision than the existing four equal divisions for more accurate structural design. 4. Structural design using wind forces close to real values is more advantageous in safety and expense.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.345-356
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• 2004

Open-cut method has been widely used to construct underground structures, but it causes several problems such as traffic congestion and public resentment resulting from severe construction noise and ground settlement. In many cases, it is very difficult to build underground structures safely due to the unknown locations of buried facilities such as water pipes, drainage pipes, gas pipes and high-pressure cable conduits etc. Also in open-cut method, moving buried facilities causes additional cost and extension of construction period. Therefore, this paper is to present a case study in which Tubular Roof construction Method (T.R.c.M.), a newly developed construction method for underground structures using slab steel pipes and PC wall trench, is applied for the construction of a subway tunnel in Seoul. As a result, it is found that T.R.c.M. is a construction method by which tunnels can be constructed safely without any effect on the surrounding environment and traffic flow due to the minimized construction vibration and noise.

• Tunnel and Underground Space
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• v.14 no.3
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• pp.188-202
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• 2004

If an underground research facility for the validation of disposal concept is constructed in KAERI, it is expected to have a thick weathered zone and varying surface topology. In this study, the influence of different geological conditions, tunnel slope, tunnel size, and sequential excavation is investigated by 3D mechanical analysis using FLAC3D. Around the tunnel, it is not expected to develop any plastic zone and the maximum stress might be as high as 5 ㎫. The maximum compressive stress will be developed at about 20 m to e dead end of the tunnel. There is no difference on stress and displacement distributions between the cases with and without sequential excavation. It is expected to have stress release in the roof and floor after the excavation of the tunnel. There is no significant influence of weathered zone size, tunnel size, and tunnel slope on the stress and displacement distributions. The modeling for the intersection shows the minimum factor of safety is above 3, when the in situ stress ratio K is 3. From the study, it was possible to demonstrate that the small scale disposal research tunnel in KAERI will be mechanically stable.

• Wind and Structures
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• v.10 no.1
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• pp.23-44
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• 2007

Wind tunnel experiments on small scale groups of tanks are reported in the paper, with the aim of evaluating the pressure patterns due to group effects. A real tank configuration is studied in detail because one tank buckled during a hurricane category 3. Three configurations are studied in a wind tunnel, two with several tanks and different wind directions, and a third one with just one blocking tank. The pressures were measured in the cylindrical part and in the roof of the tank, in order to obtain pressure coefficients. Next, computational buckling analyses were carried out for the three configurations to evaluate the buckling pressure of the target structure. Finally, imperfection-sensitivity was investigated for one of the configurations, and moderate sensitivity was found, with reductions in the maximum load of the order of 25%. The results help to explain the buckling of the tank for the levels of wind experienced during the hurricane.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.429-435
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• 2003

This paper presents the case studies of Tubular Roof construction Method(T.R.c.M) and Semi Shield method, which were applied to the tunnel excavation under the pre-existing railways. It was proved that T.R.c.M was an effective and safe method for the tunnel excavated in soft soil, giving little damage to the railways located a few meters above. Semi Shield was also performed successfully to bore a tunnel in soft and hard rock, minimizing the ground settlement and tilting of vulnerable fuel tanks. Site and soil conditions are also discussed, which led these relatively new methods to success. Finally, comparison of the measurement results and the design values are made to verify and improve the current design practice.

• Wind and Structures
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• v.25 no.6
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• pp.589-608
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• 2017

A novel probabilistic approach is presented for estimating the equivalent static wind loads that produce a static response of the structure, which is "equivalent" in a probabilistic sense, to the extreme dynamic responses due to the unsteady pressure random field induced by the wind. This approach has especially been developed for complex structures (such as stadium roofs) for which the unsteady pressure field is measured in a boundary layer wind tunnel with a turbulent incident flow. The proposed method deals with the non-Gaussian nature of the unsteady pressure random field and presents a model that yields a good representation of both the quasi-static part and the dynamical part of the structural responses. The proposed approach is experimentally validated with a relatively simple application and is then applied to a stadium roof structure for which experimental measurements of unsteady pressures have been performed in boundary layer wind tunnel.

• Journal of the Korean Professional Engineers Association
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• v.15 no.2
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• pp.3-15
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• 1982

The study on prevention measures for vibration and excavation of tunnel for the #3, #4, Seoul Subway. In the Seoul subway tunnel blasting, the drilling pattern and prevention method to seismic vibration are as follows as well as for adaptions of NATM, the supportings of roof and wall holes are arranged with control blasting. 1. The blasting is executed basically using the low velocity explosive such as slurry, Nitrate ammonium explosive, and F-I and F-II explosive for control blasting substituting of existing dynamite. 2. The cut holes are arranged with burn cut pattern and also must be arranged with M/S electrical delay caps substituting of ordinary do]ay caps. 3. Jack leg drills are used in Five Job sites and a jumbo drill in one job site. 4. In performance of safety work and in maintenance of building safety. The drilling length for blasting will not exceed 1.20 meter for round so that the vibration value shall carry below 0.3cm/sec. The harmonizing of better powder, better drilling machine and better technique is only the way of improving tunnelling efficiency and less vibration will help the dereasing of accidence.

• Wind and Structures
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• v.15 no.1
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• pp.43-64
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• 2012

Many potential small wind turbine locations are near obstacles such as buildings and shelterbelts, which can have a significant, detrimental effect on the local wind climate. A neural network-based model has been developed which predicts mean wind speed and turbulence intensity at points in an obstacle's region of influence, relative to unsheltered conditions. The neural network was trained using measurements collected in the wakes of 18 scale building models exposed to a simulated rural atmospheric boundary layer in a wind tunnel. The model obstacles covered a range of heights, widths, depths, and roof pitches typical of rural buildings. A field experiment was conducted using three unique full scale obstacles to validate model predictions and wind tunnel measurements. The accuracy of the neural network model varies with the quantity predicted and position in the obstacle wake. In general, predictions of mean velocity deficit in the far wake region are most accurate. The overall estimated mean uncertainties associated with model predictions of normalized mean wind speed and turbulence intensity are 4.9% and 12.8%, respectively.

• Tunnel and Underground Space
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• v.18 no.1
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• pp.58-68
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• 2008

The construction of an emergency spillway of Imha Dam is being in progress on the granite region including fault fractured zone. Considering that this tunnel is being excavated in three paralled rows, the pillar width between each tunnel and the face distance between each tunnel face were evaluated. The Influence of the fault fractured zone for the tunnel stability was investigated by numerical modelling in 3D. Various geophysical investigations and rock engineering field tests were carried out for these purposes. It was suitable that the second tunnel would be excavated in advance, maintaining the face distance between each tunnel face of minimum 25 m. The results of numerical modelling showed that the roof displacement and the convergence of the second tunnel were insignificant, and the maximum bending compressive stress, the maximum shear stress of shotcrete and the maximum axial force of rockbolt were also insignificant. Therefore, it was estimated that the stability of the spillway tunnel was ensured.

• Smart Structures and Systems
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• v.25 no.4
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• pp.433-446
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• 2020

In this paper the effect of confining pressure and tunnel depth on the ground vertical settlement has been investigated using particle flow code (PFC2D). For this perpuse firstly calibration of PFC2D was performed using both of tensile test and triaxial test. Then a model with dimention of 100 m × 100 m was built. A circular tunnel with diameter of 20 m was drillled in the middle of the model. Also, a rectangular tunnel with wide of 10 m and length of 20 m was drilled in the model. The center of tunnel was situated 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 45 m, 50 m, 55 m and 60 m below the ground surface. these models are under confining pressure of 0.001 GPa, 0.005 GPa, 0.01 GPa, 0.03 GPa, 0.05 GPa and 0.07 GPa. The results show that the volume of colapce zone is constant by increasing the distance between ground surface and tunnel position. Also, the volume of colapce zone was increased by decreasing of confining pressure. The maximum of settlement occurs at the top of the tunnel roof. The maximum of settlement occurs when center of tunnel was situated 15 m below the ground surface. The settlement decreases by increasing the distance between tunnel center line and measuring circles in the ground surface. The minimum of settlement occurs when center of circular tunnel was situated 60 m below the surface ground. Its to be note that the settlement increase by decreasing the confining pressure.