• Wind and Structures
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• v.36 no.2
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• pp.133-147
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• 2023

The random vibration of saddle membrane structures under wind load is studied theoretically and experimentally. First, the nonlinear random vibration differential equations of saddle membrane structures under wind loads are established based on von Karman's large deflection theory, thin shell theory and potential flow theory. The probabilistic density function (PDF) and its corresponding statistical parameters of the displacement response of membrane structure are obtained by using the diffusion process theory and the Fokker Planck Kolmogorov equation method (FPK) to solve the equation. Furthermore, a wind tunnel test is carried out to obtain the displacement time history data of the test model under wind load, and the statistical characteristics of the displacement time history of the prototype model are obtained by similarity theory and probability statistics method. Finally, the rationality of the theoretical model is verified by comparing the experimental model with the theoretical model. The results show that the theoretical model agrees with the experimental model, and the random vibration response can be effectively reduced by increasing the initial pretension force and the rise-span ratio within a certain range. The research methods can provide a theoretical reference for the random vibration of the membrane structure, and also be the foundation of structural reliability of membrane structure based on wind-induced response.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.117-126
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• 2004

Recently, the top ＆ down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a quality assurance on account of the high capacity of drilled shafts for the top ＆ down method. It seems that the capacity of drilled shaft in recent top ＆ down method is beyond that of conventional loading test method. However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. A small scale test pile can be an alternative as a quality assurance for the drilled shaft with hish capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• Journal of the Korean Society for Railway
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• v.17 no.2
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• pp.114-122
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• 2014

An asphalt trackbed is to be adapted in Korea to provide better bearing capacity and stability to the track and a comfortable ride to passengers. The dynamic modulus of Hot Mixed Asphalt(HMA) mixes is a critical design input parameter to determine the thickness of the asphalt trackbed. In this study, impact resonant tests and ultrasonic test methods are designed to obtain the dynamic modulus. These test methods are also verified to check the etffectiveness of constructing a master curve of the dynamic modulus over a wide range of frequencies and temperatures. The test results are compared to the computed dynamic modulus using AASHTO 2002 and the KPRP's proposed model. It can be concluded that the proposed simple test methods are effective to obtain the dynamic moduli of the asphalt mixes for the design of an asphalt trackbed foundation.

• Earthquakes and Structures
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• v.9 no.6
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• pp.1193-1219
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• 2015

The purpose of this study is to evaluate the seismic performance of high-rise reinforced concrete (RC) box-type wall structures commonly used for most residential buildings in Korea. For this purpose, an analytical model was calibrated with the results of the earthquake simulation tests on a 1:5 scale 10-story distorted model. This calibrated model was then transformed to a true model. The performance of the true model in terms of the stiffness, strength, and damage distribution through inelastic energy dissipation was observed with reference to the earthquake simulation test results. The model showed high overstrength factors ranging from 3 to 4. The existence of slab in this box-type wall system changed the main resistance mode in the wall from bending moment to tension/compression coupled moment through membrane actions, and increased the overall resistance capacity by about 25~35%, in comparison with the common design practice of neglecting the slab's existence. The flexibility of foundation, which is also commonly neglected in the engineering design, contributes to 30~50% of the roof drift in the stiff direction containing many walls. The possibility of concrete spalling and reinforcement buckling and fracture under the maximum considered earthquake (MCE) in Korea appears to be very low when compared with the case of the 2010 Concepcion, Chile earthquake.

• Geotechnical Engineering
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• v.11 no.3
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• pp.27-36
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• 1995

Laboratory model tests to determine the permanent settlement of a surface strip foundati on supported by geogrid -reinforced saturated clay and subjected to a low -frequency cyclic load were performed. In conducting the test, the foundation was initially subjected to an allowable static load. The cyclic load was then super -imposed over the static load. The variation of the maximum permanent settlement with the intensity of the static load and the intensity of the amplitude of the cyclic load are also presented.

• Journal of KSNVE
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• v.2 no.4
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• pp.281-292
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• 1992

Two types of vibration problems are encountered in industrial field: active isolation and passive isolation. In a passive type of vibration isolation, a foundation of a delicated machinery such as TEM, SEM, inspection- probe test, photolithograph, etc. is designed to have a vibration amplitude lower than an acceptable limit. In an active type, the isolation is focused on the vibration reduction caused by the machine itself(pump, motor, press, compressor, etc.). The foundation for such a machine should be so designed as to reduce the transmitted vibration below the permissible level prescribed. At any case, a transmissibility and stability must to be considered. Since an active isolation type is aimed for a vibration source, it is useful to isolate the transmitted vibrations energy from a major vibration source at the specific location. In this paper, a designed methodology of double anti-vibration system has been examined in order to have low transmissibility and reliable stability. Also experiment of scale model behavior has been conducted. Finally, the experiment output of the transfer function is compared to the analytical data.

• Journal of the Korean Geotechnical Society
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• v.26 no.6
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• pp.29-38
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• 2010

Micro-piles have been used to increase the bearing capacity or to restrain settlement of existing shallow foundation. Recently, micro-piles are used to support the shallow foundation, to stabilize the slope and to resist the sliding of retaining wall. Using the micro-piles in geotechnical engineering, some investigators have studied the effective installing method by model test or field test. But most of previous studies are chiefly focused on the micro-piles in sand or clay layer. If a rock layer exists in soil, the installing length of micro-piles may be determined by the depth of rock layer. In this case, the stiffness of pile may be changed by the installing length of pile, and so the installing method has to be altered by the changed stiffness of pile. Model tests have been conducted to study the installation method of micro-pile in soil with rock layer. As a result, when the ratio of length of pile is below 50 ($L/d{\leq}50$), installing of micro-piles in vertical position is effective regardless of the depth of rock layer. If the depth of rock layer is deeper than soil failure zone and the ratio of the length of pile exceeds 50 (L/d>50), installing of the micro-piles in sloped position is effective.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.905-912
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• 2009

1-g shaking table test is conducted to evaluate the dynamic behavior of a soil-structure system under seismic loading condition. A consistent similitude law between the model and prototype is needed to predict the behavior of the prototype structure, quantitatively. The natural frequency of geomaterial decreases with the increase of shaking intensity because of the non-linear property of the geomaterial. This phenomenon affects the applicability of similitude laws in 1-g shaking table tests. In this study, a simple method is suggested to determine the frequency of the input motions in 1-g tests in order to enhance the applicability of similitude laws. Modified input frequency is calculated using the frequency ratio with consideration of the variation of the natural frequency according to the intensity of input ground acceleration. To verify the applicability of the suggested method, a series of 1-g shaking table tests were performed for three different sizes of model piles having an overburden mass on their heads by varying the acceleration and the frequency of input motion. The acceleration amplification ratio on the overburden mass, the lateral displacement at the pile head and the maximum bending moment along the pile depth were measured. The projected behaviors of the virtual prototype based on the measured values of the model tests, where the input frequencies were calculated by the new method, showed good consistency, verifying the applicability of the suggested method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1439-1444
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• 1994

Laboratory model test results for the ultimate bearing capacity and allowable bearing capacity at various settlement levels conducted on a strip foundation supported by geogrid-reinforced clay soil have been presented. For mobilization of the maximum possible load-carrying capacity, the optimum width and depth of the reinforcement layers, and the location of the first layer of reinforcement with respect to the bottom of the foundation have been determined.

• Geomechanics and Engineering
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• v.4 no.3
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• pp.191-208
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• 2012

Due to rapid industrialisation, large scale infrastructure development is taking place worldwide. This includes railways, high speed highways, elevated roads etc. To meet the demands of society and industry, many innovative techniques and materials are being developed. In developed nations like USA, Japan etc. for railways applications, new material like geocells, geogrids are being used successfully to enable fast movement of vehicles. The present research work was aimed to develop design methodologies for improvement of grounds subjected to cyclic loads caused by moving vehicles on roads, rail tracks etc. Deformation behavior of ballast under static and cyclic load tests was studied based on square footing test. The paper presents a study of the effect of geo-synthetic reinforcement on the (cumulative) plastic settlement, of point loaded square footing on a thick layer of granular base overlying different compressible bases. The research findings showed that inclusion of geo-synthetics significantly improves the performance of ballasted tracks and reduces the foundation area. If the area is kept same, higher speed trains can be allowed to pass through the same track with insertion of geosynthetics. Similarly, area of machine foundation may also be reduced where geosynthetics is provided in foundation. The model tests results have been validated by numerical modeling, using $FLAC^{3D}$.