• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.271-282
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• 2008

Specific joint devices composed of end-plates and through bolts are under development to assemble steel beams to PC columns efficiently by dry construction method for the PCS structural system, of which major structural components are precast concrete columns and steel beams. Seismic performance of the joint devices had been evaluated by experimental tests in the previous studies and it was showed that all the performance requirements regarding to strength deterioration, stiffness degradation and energy dissipation capacity were satisfied to the criteria of ACI requirements, but the initial stiffness was not. In order to find out possible causes of the insufficient rigidity of the joint devices and provide the proper measures to improve the performance of the joint accordingly, numerical analyses were carried out by using ABAQUS. Parameters, such as thickness of neoprene pad, conditions of surface between PC column and end-plate, magnitude of pretension forces of through bolts, stiffness of end-plate were taken into consideration. As the result, it was found that the rigidity of the PCS system was negatively affected by the magnitude of initial gaps between PC columns and end-plates, and insufficient stiffness of neoprene fillers and end plates. In order to improve the initial stiffness performance of the joints, measures such as increase of the magnitude of pretension forces on through bolts and increase of the stiffness of end-plate by reducing the bolt pitch and providing adequate stiffeners are recommended.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.215-225
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• 2011

In general, the precast columns can obtain its homogeneous quality as they are produced in a factory with a hollow concrete block type by using high strength concrete, so that they can generate the reduction of dead load. Such a method of precast hollow concrete columns is already implemented in USA and Japan and used for connecting between blocks which use PC tendons. However, it is inevitable to have uneconomical construction with excessive cost in early stage when PC tendons are used. This study aims to develop an economical precast column with high quality and constructability which consists of only splice sleeve and general reinforcing bar without using PC tendons in order to reduce the construction period and cost. To achieve this goal, this study tested the performance of total 5 minimized models in the experiment with the variables such as hollowness, diameter of main reinforcement bar and cross-sectional size for the cross section of precast column by using grouting type splice sleeve which is a new type joint rebar. And it also verified the performance of column in the experiment for a large-sized model in order to overview its applicability by excluding large scale effect.

• Journal of the Korea Concrete Institute
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• v.25 no.6
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• pp.631-639
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• 2013

Non-linear finite element analysis for newly developed precast concrete details for beam-to-column connection which can be used in moderate seismic region was carried out in this study. Developed precast system is based on composite structure and which have steel tube in column and steel plate in beam. Improving cracking strength of joint under reversed cyclic loading, joint area was casted with ECC (Engineering Cementitious Composites). Since this newly developed precast system have complex sectional properties and newly developed material, new analysis method should be developed. Using embedded elements and models of non-linear finite element analysis program ABAQUS previously tested specimens were successfully analyzed. Analysis results show comparatively accurate and conservative prediction. Using finite element model, effect of axial load magnitude and flexural strength ratio were investigated. Developed connection have optimized performance under axial load of 10~20% of compressive strength of column. Plastic hinge was successfully developed with flexural strength ratio greater than 1.2.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.41-54
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• 2011

The present study analyzes the stability of waterfront quay wall under the combined action of earthquake and tsunami. Adopting the limit equilibrium method, the stability of waterfront quay wall is checked for both the sliding and overturning. Forces due to tsunami are compared with the proposed formula and the 3-D one-field Model for immiscible TWO-Phase flows (TWOPM-3D). Variations of the stability of wall are also proposed by the parametric study including tsunami water height, horizontal seismic acceleration coefficient, internal friction angle of soil, friction angle between the wall and the soil and the pore water pressure ratio. The present study about the stability of wall is also compared with the case when earthquake and tsunami are not considered. As a result, the result of numerical analysis about the tsunami force is similar to that of proposed formula. When earthquake and tsunami are simultaneously considered, the stability of wall in passive case significantly decreases and tsunami forces in active case are affected as a resistance force on the wall and so the stability of wall increases.

• Explosives and Blasting
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• v.18 no.2
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• pp.7-13
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• 2000

Abstract The characteristics of bed rock in the study area was classified by means of the crack coefficient estimated from the seismic velocities of in-situ and intact rocks. Various statistical methods were investigated in order to minimize the possible errors in estimating the predictive equation of blasting vibration and to enhance the determination coefficient $R^2$, for more reliable estimation. The determination coefficient showed the highest in the analysis for those groups using weighting function with the number of samples. The analysis for the weighting function employed with standard coefficient and variance also enhanced the determination coefficients significantly compared to the others, but the reliability was slightly lower than results obtained former method. Therefore the most reliable predictive equation of blasting vibration was found to be obtained from a regression analysis of the mean vibration level using the weighting of same distance groups within 15m with the same explosive charge weight per delay. The coefficients, K and n 317.4 and -1.66, respectively, when using the square root scaling, and 209.9 and -1.66, respectively, when using the cube root scaling. The analysis also showed that the square root scaling may be used in the distance less than 31m form the blast source, and the cube root scaling in the distance more than 31m for safe design.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.349-356
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• 2015

Although geophysical methods are useful and generally provide valuable information about the subsurface, it is important to recognize their limitations. A common limitation is the lack of sufficient contrast in physical properties between different layers. Thus, multiple methods are commonly used to best constrain the physical properties of different layers and interpret each section individually. Ground penetrating radar (GPR) and shallow seismic reflection (SSR) methods, used for shallow and very shallow subsurface imaging, respond to dielectric and velocity contrasts between layers, respectively. In this study, we merged GPR and SSR data from a test site within the Cheongui granitic mass, where the water table is ~3 m deep all year. We interpreted the data in combination with field observations and existing data from drill cores and well logs. GPR and SSR reflections from the tops of the sand layer, water table, and weathered and soft rocks are successfully mapped in a single section, and they correlate well with electrical resistivity data and SPS (suspension PS) well-logging profiles. In addition, subsurface interfaces in the integrated section correlate well with S-wave velocity structures from multi-channel analysis shear wave (MASW) data, a method that was recently developed to enhance lateral resolution on the basis of CMP (common midpoint) cross-correlation (CMPCC) analysis.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.393-402
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• 1995

The structural analysis of the reactor coolant system mainly consist of too fields. The one is the static analysis considering the impact of pressure and temperature built up during normal operation. The other is the dynamic analysis to estimate the impact of postulated events such as the seismic loads or postulated branch line pipe breaks event. Since the most important goal of the RCS structural analysis is to prove the safety of the RCS during normal operation or postulated events, a widely proven theory having enough conservatism is adopted. The load occurring on the RCS during normal operation is considered as the basic design loading condition throughout whole plant life time. The most typical characteristic of the RCS during normal operation is the thermal expansion of the RCS caused by reactor coolant with high temperature and pressure. Therefore, the exact estimation on the thermal movement of the RCS is needed to get more clear understanding on the thermal movement behavior of the RCS. In this study, the general structural analysis concept and modeling method to evaluate the thermal movement of the RCS under the normal plant operation condition are presented. To discuss the validation of the suggested analysis, analysis results are compared with the measured data which ore referred from the standardized 1000 MWe PWR plant under construction.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.9-16
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• 2006

The design practice of the lateral resisting system has been traditionally dependent on the experience and know-how of a structural engineer. And the method to reflect the evaluation results of building's capacity on design process doesn't exist. The proposal of a rational design of the lateral load resisting system is based on the available full capacity $(R_{ac})$ of a building and the minimum required capacity $(R_{code})$ suggested in the code. This study suggests thai nonlinear static analysis, which is the estimation of the lateral capacity with the pushover analysis, be included in the existing design procedure of the structure. After finishing the basic structural design, the lateral resisting capacity ol a building is estimated. At the phase of nonlinear static analysis, pushover analysis is peformed to define the fully yielded baseshear $(V_Y)$. When the design wind baseshear $(V_{wind})$ is bigger than the design seismic baseshear $(V_D)$, the value is checked to determine whether or not it is smaller than the $V_Y$. After confirming that it is smaller, the $R_{ac}$ of the structure is computed. If the $V_D$ is bigger at first, only the $R_{ac}$ is computed. When the value of the estimation shows remarkable differences with the $R_{code}$, repetition of the design modification is needed for those approximate to the $R_{code}$. Application of the proposed design procedure to 2-D steel braced RC buildings has proven to be efficient.

• Geophysics and Geophysical Exploration
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• v.18 no.1
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• pp.1-8
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• 2015

To estimate the shear-wave velocity (${\nu}_s$ beneath the OTVZ seismic station on Ngauruhoe volcano in New Zealand, we calculated receiver functions (RFs) using 127 teleseismic data ($Mw{\geq}5.5$) with high signal-to-noise ratios recorded during November 11, 2011 to September 11, 2013. The genetic inversion algorithms was applied to 21 RFs calculated by the iterative time-domain deconvolution method. In the 1-D ${\nu}_s$ model derived by the inversion, the Moho is observed at a 14 km depth, marked by a ${\nu}_s$ transition from 3.7 km/s to 4.7 km/s. The average ${\nu}_s$ of the overlying crust is 3.4 km/s, and the average ${\nu}_s$ of a greater than 9-km thick low-velocity layer (LVL) in the lower crust is 3.1 km/s. The LVL becomes thinner with increasing distance from the station. Another LVL thicker than 10 km with ${\nu}_s$ less than 4.3 km/s is found in the upper mantle. Those LVLs in the lower crust and the upper mantle and the relatively thin crust might be related to the magma activity caused by the subducting Pacific plate.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.125-134
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• 2006

Conventional methods for the assessment of liquefaction potential were primary for severe earthquake regions $(M{\geq}7.5)$ such as North America and Japan. In Korea, an earthquake related research has started in 1997, but most contents in the guidelines were still quoted from literature reviews of North America and Japan, which are located in strong earthquake region. Those are not proper in a moderate earthquake regions including Korea. Also the equivalent uniform stress concept (Seed & Idriss, 1971) using regular sinusoidal loading which is used, in a conventional method for the assessment of liquefaction potential, can't reflect correctly the dynamic characteristics of real irregular earthquake motions. In this study, cyclic triaxial tests using irregular earthquake motions are performed with different earthquake magnitudes, relative densities, and fines contents. Assessment of liquefaction potential in moderate earthquake regions is discussed based on various laboratory test results. From the results, screening limits in seismic design were re-investigated and proposed using normalized maximum stress ratios under real irregular earthquake motions. Also from the tests using constant wedge loading and incremental wedge loading, the characteristics of liquefaction resistance of saturated sand under irregular ground motions are investigated.