• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.43-51
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• 2014

A Large-diameter drilled shaft of deep water depth composite foundation supporting a high rise pylon of the test designed super long span bridge was designed by allowable stress design method and failure probability through reliability analysis to bearing capacity was estimated. The allowable stress design results for the bearing capacity of a drilled shaft were analyzed by reliability analysis and the probability of failure shows 0.12 % in case of CFEM, 0.0002 % in case of Korea Highway Corporation criterion, and 0.003 % in case of structure foundation design criterion. In the allowable stress design, the bearing capacity of a large-diameter drilled shaft was obtained by applying to safety factor 3 and reliability analysis for the results was done. If the failure probability suggested by AASHTO(2007) specification is set to 0.02 %, the socketed length of a drilled shaft shows an increase of 25 % in CFEM, decrease of 60 % in KHCC, and decrease of 89 % in SFDC.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.51-60
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• 2021

River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4845-4852
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• 2012

This research calculated the scour depth of bridge according to inflow and outflow changes of stream's flood discharge and curves by applying scour depth formula for piers and abutments, and by comparing and examining them, evaluated the applicability of scour depth formulas. Overall, if the angles of flood discharge and inflow and outflow increase, the deviation rate of scour depth in bight increased. Especially the deviation rate was 58% at the inflow and outflow angle of $105^{\circ}$ that the bridge plan for this geography need careful examination. Next, as a result of calculating the deviation rate of scour depth at the bight by scour depth formulas, in case of pier, Andru formula showed 58% deviation rate, Laursen formula showed 26% deviation rate, and CSU. formula showed 17% deviation rate. In the case of abutment, Froehlich formula shows 44% deviation rate that when applying above scour depth formulas, scour depth calculation considering repairable characteristics of bight is necessary. Finally, about inflow and outflow angles of $45^{\circ}{\sim}135^{\circ}$ that showed big deviation rate of scour depth, this research performed regression analysis of deviation rates of scour depth due to flood discharge to suggest the regression formula.

• The Journal of Engineering Geology
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• v.6 no.1
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• pp.15-22
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• 1996

Frequency content of seismic waves observed in field seismic survey in Korea has almost not exceeded 4kHz(wave length 1m). The limited frequency content not only restricts the minimum size of objects which can be surveyed in seismic tomogrpahic application, but also makes a fundamental limit in the resolution of tomogram. This paper shows the resonable result obtained by confirmimg and resolving the problems which can be occured m measuring procedure for the small - sized section through field application. Seismic tomographic field survey was performed for a concrete construction for railroad bridge in Korea, and to this the tomographic measurements for the stone-build foundation construction for a bell house of church in Germany were compared.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.389-396
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• 1999

In this study compressive and tensile load tests have been performed to investigate reinforcing effect and load transfer mechanism of small diameter piles installed in the foundation soil for the marine suspension bridge. Load tests were carried out on steel plate with diameters of 50cm, 100cm and 150cm varying loads starting from 39 tons up to 314 tons. Small diameter piles were proved to behavior like as friction piles and loads were not transmitted to the bottom of piles. From pull-out tests, the uplift capacity of small diameter piles was largely influenced by reinforcing materials compared to frictional resistance between piles and adjacent soils. The bearing capacity of small diameter piles appeared to be higher than the ultimate bearing capacity evaluated using static formulae. The load carrying capacity of small diameter piles was superior to the bored piles with a similar size. Thus, ultimate bearing capacity estimated from static formulae can provide conservative designs and thereby resulting in economic disadvantages. A further study to accumulate data regarding various soil conditions is recommended for an improved estimation of bearing capacity of piles with small diameter.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1138-1142
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• 2005

The tidal river is a river affected by tide, which causes the water level to rise and fall two times everyday periodically. The local velocity across the river could be very fast because of the cross-sectional characteristics of the river even though it's not a rainy season. Therefore extreme local scour could take place around hydraulic structures such as piers and caissons due to backward flow velocity. For the construction of pier foundation of Ilsan-bridge In the Han River, the field observations were performed to get the velocity and water level. The numerical analysis was performed by HEC-RAS(UNET). The relationship between measured maximum velocity and calculated mean velocity is achieved, which is used to estimate the velocity and water level as the construction is proceeding. Countermeasures for scour were designed with the results of the hydraulic analysis to avoid potential damage during construction work. According to the results of monitoring, the velocity increase after temporary road embankment was negligible, from which it is considered that the degradation of main channel compensated for the constriction of cross-section by embankment.

• Journal of Korean Institute of Industrial Engineers
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• v.40 no.5
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• pp.462-476
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• 2014

The Korean government has been implementing diverse policies with programs to generate better outcomes and results of university-industry collaboration since 1990s. In this paper, we analyze the effect of universities' competency factors on the performance of technology commercialization and start-ups respectively. We employ multiple regression models using 154 data sets from university information posting system of the Korean Council for University Education. Through conducting statistical analyses with diverse data manipulations, we obtained a high degree of significance on hypotheses, and also could compare mutual differences between the effects of university competence on technology commercialization and start-ups. The technology transfer and commercialization specifically depends on professors' patent applications and technology holding company, while start-ups does professionals in industry-university cooperation. We suggest government to spur on the ongoing customization of university-industry collaboration policy, and university to properly cope with global atmosphere changing from ivory tower to academic capitalism and start-ups promotion.

• Land and Housing Review
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• v.11 no.2
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• pp.75-86
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• 2020

As the urban regeneration project and the old housing maintenance project are actively progressing in Korea, small-scale building construction is being carried out in downtown areas. Small buildings in the downtown area are constructed on about 4 to 10 floors, and since they are carried out in small units in residential areas, it is difficult to enter large equipment to construct existing piles, and it is more vulnerable to complaints about noise and vibration. in this study, helical piles suitable for urban areas or small sites where it is difficult to enter large equipment, such as noise and vibration. Reliability analysis was performed on the results of the static load tests and dynamic load tests conducted at the LH site and the bearing capacity calculated by the hydrostatic method and the empirical formula (N value). As a result of comparing and analyzing the design formula and the results of static load test and dynamic load tests, the correlation between the design formula of the bored pile (Road bridge design standard) formula using N value and the design formula by the modified Davisson method frequently used by method commonly European helical file practitioners.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.1
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• pp.142-156
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• 2015

A new method for ship Inner Shell optimization, which is called Parametric Inner Shell Optimization Method (PISOM), is presented in this paper in order to improve both hull performance and design efficiency of transport ship. The foundation of PISOM is the parametric Inner Shell Plate (ISP) model, which is a fully-associative model driven by dimensions. A method to create parametric ISP model is proposed, including geometric primitives, geometric constraints, geometric constraint solving etc. The standard optimization procedure of ship ISP optimization based on parametric ISP model is put forward, and an efficient optimization approach for typical transport ship is developed based on this procedure. This approach takes the section area of ISP and the other dominant parameters as variables, while all the design requirements such as propeller immersion, fore bottom wave slap, bridge visibility, longitudinal strength etc, are made constraints. The optimization objective is maximum volume of cargo oil tanker/cargo hold, and the genetic algorithm is used to solve this optimization model. This method is applied to the optimization of a product oil tanker and a bulk carrier, and it is proved to be effective, highly efficient, and engineering practical.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.275-282
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• 2013

Applications such as vibration isolation, gravity compensation, pick-and-place machines, etc., would benefit from (long-stroke) cylindrical/tubular permanent magnet (PM) actuators with integrated passive gravity compensation to minimize the power consumption. As an example, in component placing (pick-and-place) machines on printed circuit boards, passive devices allow the powerless counteraction of translator including nozzles or tooling bits. In these applications, an increasing demand is arising for high-speed actuation with high precision and bandwidth capability mainly due to the placement head being at the foundation of the motion chain, hence, a large mass of this device will result in high force/power requirements for the driving mechanism (i.e. an H-bridge with three linear permanent magnet motors placed in an H-configuration). This paper investigates a tubular actuator topology combined with passive gravity compensation. These two functionalities are separately introduced, where the combination is verified using comprehensive three dimensional (3D) finite element analyses.