• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.67-77
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• 2008

Seismic isolation has been studied continuously as a solution of the seismic engineering to reduce the sectional forces and the damages of structures caused by earthquakes. To certify reliable design and installation of the seismic isolation systems, seismic isolation bearings should be fabricated under well planned quality control process, and proper evaluation tests for their seismic performance should be followed. In this study, shear property evaluation tests for the lead rubber bearings(LRB) and the rubber bearings(RB) were implemented and the temperature dependency tests were also implemented to evaluate the changes of shear properties according to the changes of temperature. After evaluation tests, the measured shear properties were compared to their design values and their deviation was analyzed comparing with the allowable error ranges specified in Highway Bridge Design Specifications. These results showed that a considerable number of isolation bearings have so large deviations from their design values that their error ranges were over or very close to the allowable ranges. And the test results for temperature dependency showed that the shear properties of isolation bearings would be changed in great degree by the change of temperature during their service period. If these two types of changes in their shear properties are superposed, it would possible that the changes of shear properties from their original design values are over than 50%.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.5-16
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• 2012

Geotechnical buried structures with relatively light weight have been suffering from uplift damage due to liquefaction in the past earthquakes. The factor of safety approach by Koseki et al. (1997a), which is widely used in seismic design, predicts the triggering of uplift. However, a method for "quantitative" estimates of the uplift displacement has yet to be established. Estimation of the uplift displacement may be an important factor to be considered for designing underground structures under the framework of performance-based design (ISO23469, 2005). Therefore, evaluation of the uplift displacement of buried structure in liquefied ground during earthquakes is needed for a performance-based design as a practical application. In order to predict the uplift displacement quantitatively, a simplified method is derived based on the equilibrium of vertical forces acting on buried structures in backfill during earthquakes (Tobita et al., 2012). The method is verified through comparisons with results of centrifuge model tests and damaged sewerage systems after the 2004 Niigata-ken Chuetsu, Japan, earthquake. The proposed flow diagram for performance-based design includes estimation of the uplift displacement as well as liquefaction limit of backfill.

• Journal of the Earthquake Engineering Society of Korea
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• v.21 no.4
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• pp.189-195
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• 2017

In the seismic design of building structural members, due to the complexity of the placement of PC steels in prestressed concrete members, it is necessary to review and define the definition of member damage in comparison with reinforced concrete members. In this study, the results of past experiments compared with the calculation results by 'section Analysis Method', with the aim of reviewing the precision of calculation results when member damage evaluation is performed using the section analysis method. Furthermore, it is also compared with the calculation results by the 'split Element Method'. In addition, parametric studies were carried out, and the influence of the difference between the amount of PC steels and reinforced bar on the residual strain was examined.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.412-421
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• 2013

Nowadays, small and medium-sized earthquakes occur frequently in the west coast of Korea. The earthquake induced damages on the harbor structure such as quay wall possibly make a severe impact on national economy. Therefore, not only a seismic design for the structures but warning system for seismic damage right after the occurrence of earthquake should be developed. In this study, seismic fragility analysis was performed to be given to earthquake damage prediction system for quay wall structures in Busan and Incheon harbor. Four types of structures such as pier-type, caisson type, counterfort type, block-type were analyzed and fragility curves of functional performance level and collapse prevention level based on displacement criteria were found. Regression analyses by using the results of the two ports were done for possible use in other port structures.

• 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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.1009-1015
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• 2012

Valves are one of the most important components of a pipeline system in a nuclear power plant, and it is important to ensure their structural safety under seismic loads. A crucial aspect of structural safety verification is the seismic qualification, and therefore, an optimal shape design and experimental seismic qualification is necessary in case the configuration of the valve parts needs to be modified and their performance needs to be improved. Recently, intensive numerical analyses have been performed before the experimental verification in order to determine the appropriate design variables that satisfy the performance requirements under seismic loads. In this study, static and dynamic numerical structural analyses of a 200A butterfly valve for a nuclear power plant were performed according to the KEPIC MFA. The result of static analysis considering an equivalent static load under SSE condition gave an applied stress of 135 MPa. In addition, the result of dynamic analysis gave an applied stress of 183 MPa, where the CQC method using response spectrums was taken into account. These values are under the allowable strength of the materials used for manufacturing the butterfly valve, and therefore, its structural safety satisfies the requirements of KEPIC MFA.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.149-164
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• 2021

Most of high-rise buildings in Japan^*1 are structure with damping systems recently. The design procedure is performance-based design (PBD), which is based on the nonlinear response history procedure (NRHP) using 2 or 3-dimentional frame model. In addition, hysteretic property of steel plates or velocity-dependent property of viscous dampers are common practice for the damping system. However, for the selection of damping system, the easy dynamic analysis of recent date may lead the most of engineers to focus attention on the maximum response only without thinking how it shakes. By nature, the seismic design shall be to figure out the action of inertia forces by complex & dynamic loads including periodic and pulse-like characteristics, what we call seismic ground motion. And it shall be done under the dynamic condition. On the contrary, we engineers engineers have constructed the easy-to-use static loads and devoted ourselves to handle them. The structures with damping system shall be designed considering how the stiffness & damping to be applied to the structures against the inertia forces with the viewpoint of dynamic aspect. In this paper we reconsider the role of damping in vibration and give much thought to the basic of shake with damping from a standpoint of structural design. Then, we present some design examples based on them.

• The Journal of the Convergence on Culture Technology
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• v.4 no.1
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• pp.307-314
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• 2018

It became clear that Korean peninsula is not a safe region anymore from an earthquake disaster after Gyeongju and Pohang Earthquake in 2016-2017. Unfortunately, building industry in Korea has not been well prepared for an earthquake disaster and the following problems exist. First, the rate of buildings with proper seismic performance is relatively low. Second, the number of piloti buildings which are vulnerable to earthquake and fire disaster has increased recently. Third, the proportion of small-scale buildings excluded from the application of the building law for securing safety is too high. Fourth, widespread corruption and poor construction impede safety. Therefore, measures to prepare for earthquake disaster are as follows. First, methods of reinforcing building structures and reducing the seismic load acting on a building should be utilized in order to secure the insufficient seismic performance of buildings vulnerable to earthquakes. Second, whistleblowers should be encouraged and protected to prevent defective construction due to corruption. To this end, whistleblowers should be recognized as an effective means of protecting public interest not the traitor to the organization.

• International Journal of High-Rise Buildings
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• v.5 no.1
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• pp.1-12
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• 2016

The 1100 foot [335 m] tall Wilshire Grand Center tower under construction in Los Angeles illustrates many key outrigger issues. The tower has a long, narrow floor plan and slender central core. Outrigger braces at three groups of levels in the tower help provide for occupant comfort during windy conditions as well as safety during earthquakes. Because outrigger systems are outside the scope of prescriptive code provisions, Performance Based Design (PBD) using Nonlinear Response History Analysis (NRHA) demonstrated acceptability to the Los Angeles building department and its peer review panel. Buckling Restrained Brace (BRB) diagonals are used at all outrigger levels to provide stable cyclic nonlinear behavior and to limit forces generated at columns, connections and core walls. Each diagonal at the lowest set of outriggers includes four individual BRBs to provide exceptional capacities. The middle outriggers have an unusual 'X-braced Vierendeel' configuration to provide clear hotel corridors. The top outriggers are pre-loaded by jacks to address long-term differential shortening between the concrete core and concrete-filled steel perimeter box columns. The outrigger connection details are complex in order to handle large forces and deformations, but were developed with contractor input to enable practical construction.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.4
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• pp.157-167
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• 2020

In this study, a field bridge test was conducted to find the dynamic properties of cable supported bridges with resilient-friction base isolation systems (R-FBI). Various ambient vibration tests were performed to estimate dynamic properties of a test bridge using trucks in a non-transportation state before opening of the bridge and by ordinary traffic loadings about one year later after opening of the bridge. The dynamic properties found from the results of the tests were compared with an analysis model. From the result of the ambient vibration tests of the cable supported bridge with R-FBI, it was confirmed that the dynamic properties were sensitive to the stiffness of the R-FBI in the bridge, and the seismic analysis model of the test bridge using the effective stiffness of the R-FBI was insufficient for reflecting the dynamic behavior of the bridge. In the case of cable supported bridges, the seismic design must follow the "Korean Highway Bridge Design Code (Limit State Design) for Cable supported bridges." Therefore, in order to reflect the actual behavior characteristics of the R-FBI installed on cable-supported bridges, an improved seismic design procedure should be proposed.