• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.15 no.1
• /
• pp.53-61
• /
• 2019

The seismic capacity of electric cabinets in Nuclear Power Plants (NPPs) should be qualified before installation and be maintained during operation. However it can happen that identical devices cannnot be produced for replacement of devices mounted in electric cabinets. In case of when no In-Cabinet Response Spectrum (ICRS) is available for new devices, ICRS can be generated by using Finite Element Analysis (FEA). In this study we investigate structural response and ICRSs of battery charger which is supplied to NPPs. Test results on the battery charger are utilized in this study. The response is measured by accelerometers installed on the housing of the battery charger and local panels in the battery charger. Numerical analysis model is established based on resonant frequency search test results and validated by comparison with 2 types of earthquake testing results. ICRSs produced from the numerical model are compared with measured ICRSs in the seismic tests. Developed analysis model is a simple reduced model and anticipates ICRSs quite well as measured response in the tests overall despite of its structural limitation.

• Structural Engineering and Mechanics
• /
• v.84 no.5
• /
• pp.591-604
• /
• 2022

A gravity wall combined with an anchoring lattice frame (a combined retaining structure) is adopted at a typical engineering site at Dali-Ruili Railway Line China. Where, the combined retaining structure supports a soil deposit covering on different inclined rock slopes. With an aim to investigate and compare the effects of inclined rock slopes on the response of combined retaining structure under seismic excitation, three groups of shaking table tests are conducted. The rock slopes are shaped as planar surfaces inclined at angles of 20°, 30°, and 40° with the horizontal, respectively. The shaking table tests are supplemented by dynamic numerical simulations. The results regarding the horizontal acceleration response, vertical acceleration response, permanent displacement mode, and axial anchor force are comparatively examined. The acceleration response is more susceptible to outer structural profile of combined retaining structure than to inclined angle of rock slope. The permanent displacement decreases when the inclined angle of the rock slope increases within a range of 20°-40°. A critical inclined angle of rock slope exists within a range of 20°-40°, and induces the largest axial anchor force in the combined retaining structure.

• Journal of Korean Association for Spatial Structures
• /
• v.16 no.1
• /
• pp.95-104
• /
• 2016

Recently, the concept of damped outrigger system has been proposed for tall buildings. But, structural characteristics and design method of this system were not sufficiently investigated to date. In this study, the dynamic response control performance of outrigger damper has been analyzed. To this end, a simplified analysis model with outrigger damper system has been developed. Use the El Centro seismic(1940, NS) analysis was performed. Analysis results, on the top floor displacement response to the earthquake response, did not have a big effect. However, acceleration response control effect was found to be excellent. The increase of outrigger damper capacity usually results in the improved control performance. However, it is necessary to select that proper stiffness and damping values of the outrigger damper system because, the outrigger damper having large capacity is result in heavy financial burden.

• Earthquakes and Structures
• /
• v.8 no.6
• /
• pp.1349-1362
• /
• 2015

This paper presents an analytical study aimed at evaluating the effectiveness of using buckling-restrained braces (BRBs) in mitigating the seismic response of a case study 6 storey reinforced concrete (RC) building. In the design of the BRBs with non-prismatic cross-sections, twelve combinations of ${\alpha}$ and ${\beta}$ design parameters that influence the strength and stiffness of the BRBs, respectively, were considered. The response of the structure with and without BRBs under earthquake ground accelerations were evaluated through nonlinear dynamic analysis. Two sets of ground motions representative of the design earthquake with 10% and 50% exceedance probability in fifty years were taken into account. By comparing the structural performance of the original and buckling restrained braced structures, it was observed that the use of the BRBs were very effective in mitigating the seismic response as a retrofit scheme. However, the selection of the strength and stiffness parameters of the BRBs had considerable effect on the response characteristics of RC structures. For instance, by increasing the value of ${\alpha}$ and by decreasing the value of ${\beta}$ of the buckling-restrained braces, the maximum deformation demand of the structures increased.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.37 no.4
• /
• pp.251-258
• /
• 2024

This study investigated the effect of bearing aging on the seismic response of a three-span continuous concrete girder bridge with pot bearings installed. The pot bearings were modeled as elastic springs in the longitudinal, transverse, and vertical directions of the bridge to reflect the stiffness of fixed and movable supports. The effect of bearing aging on the seismic response of the bridge was examined by considering two factors: a decrease in the horizontal stiffness of the fixed bearings and an increase in the horizontal stiffness of the movable bearings. The finite element model of the three-span continuous girder bridge was validated by comparing its numerical natural frequencies with the designed natural frequencies. Using artificial ground motions that conform to the design response spectrum specified by the KDS bridge seismic design code, the seismic responses of the bridge's girders and bearings were calculated, considering the bearing stiffness variation due to aging. The results of a numerical analysis revealed that a decrease in the horizontal stiffness of the fixed bearings led to an increase in the absolute maximum relative displacement of the bearings during an earthquake. This increases the risk of the mortar block that supports the bearing cracking and the anchor bolt breaking. However, an increase in the horizontal stiffness of the movable bearings due to aging decreased the absolute maximum shear on the fixed bearings. Despite the shear reduction in the fixed bearings, the aging of the pot bearings change could cause additional tensile bending stress in the girder section above the free bearings, which could lead to unexpected structural damage to the continuous bridge during an earthquake.

• Earthquakes and Structures
• /
• v.24 no.6
• /
• pp.429-437
• /
• 2023

This paper studied the prediction of structural damage indices to buildings after earthquake occurrence using Multiple Linear Regression (MLR) and Fuzzy Linear Regression (FLR) methods. Particularly, the structural damage degree, represented by the Maximum Inter Story Drift Ratio (MISDR), is an essential factor that ensures the safety of the building. Thus, the seismic response of a steel building was evaluated, utilizing 65 seismic accelerograms as input signals. Among the several response quantities, the focus is on the MISDR, which expresses the postseismic damage status. Using MLR and FLR methods and comparing the outputs with the corresponding evaluated by nonlinear dynamic analyses, it was concluded that the FLR method had the most accurate prediction results in contrast to the MLR method. A blind prediction applying a set of another 10 artificial accelerograms also examined the model's effectiveness. The results revealed that the use of the FLR method had the smallest average percentage error level for every set of applied accelerograms, and thus it is a suitable modeling tool in earthquake engineering.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.10a
• /
• pp.346-353
• /
• 2002

The risk of bearing failure is evaluated through the seismic response analysis of a bridge considering the probabilistic characteristics of structural properties such as the mass of superstructure, the stiffness of pier, and the translational and rotational stiffness of the foundation as well as seismic loadings during the bridge service lift. The effect of pounding between adjacent vibration units on the risk of bearing failure is also investigated. The probabilistic characteristics of structural properties are obtained by the Monte Carlo simulations based on the probabilistic characteristics of basic random variables included in the structural properties. From the simulation results, the failure probability of fixed bearings attached on the abutment is found to be much higher than those placed on the piers. It is also found that the pounding effect significantly increases the failure probability of bearings. In the simply supported bridges, the risk of bearing failure increases as the number of bridge spans increase. Therefore, the failure probability of fixed bearing due to the effects of pounding phenomena and the number of bridge spans should be considered in the seismic desist of bearings.

• Land and Housing Review
• /
• v.5 no.2
• /
• pp.107-114
• /
• 2014

Passive energy dissipation systems for seismic applications have been under development for a number of years with a rapid increase in implementations starting in the mid-1990s in many countries. A metallic hysteretic damper has most commonly been used for seismic protection of structures in domestic area because they present high energy-dissipation potential at relatively low cost and easy to install and maintain. This paper presents an analytical case study of the effectiveness of isotropic hysteretic metallic damper(IHMD) called Kagome as a passive dissipative device in reducing structural response during seismic excitation. An eighteen-story RC framed apartment building is studied with and without IHMD. Results demonstrate the feasibility of these techniques for seismic mitigation. The inclusion of supplemental passive energy dissipation devices in the form of IHMD proved to be a very effective method for significantly reducing the seismic response of the building investigated.

• Structural Engineering and Mechanics
• /
• v.91 no.5
• /
• pp.487-502
• /
• 2024

This study introduces a novel 'multi-mushroom' structural system designed to improve seismic performance in lowrise buildings. Traditional low-rise structures tend to favor sliding over rocking due to their smaller aspect ratios despite the rocking system's superior seismic response reduction. Rocking designs allow structures to pivot at their base during seismic events, reducing damage by dissipating energy. The proposed multi-mushroom system divides the building into four equal sections with small gaps in between, each capable of independent rocking. Numerical analyses are conducted using scaled earthquake records from far- and near-source events to evaluate this system's performance. The results indicated that the multimushroom system significantly reduces plastic hinge formation compared to conventional designs. The system also demonstrated enhanced beam performance and a robust base girder, contributing to reduced collapse vulnerability. The 3-story model exhibited the most favorable behavior, effectively mitigating peak roof drift values, where the rocking system achieved a 21% reduction in mean roof displacement for near-field records and 15% for far-field records. However, the 5-story configuration showed increased roof displacement, and the 7-story model recorded higher incidences of collapse prevention (CP) hinges, indicating areas for further optimization. Overall, the multi-mushroom system enhances seismic resilience by minimizing plastic hinge formation and improving structural integrity. While the system shows significant promise for low-rise buildings, challenges related to roof displacement and inter-story drift ratio in taller structures necessitate further research. These findings suggest that the multi-mushroom system offers a viable solution for seismic risk reduction, contributing to safer and more sustainable urban development in earthquake-prone areas.

• Earthquakes and Structures
• /
• v.5 no.6
• /
• pp.657-678
• /
• 2013

For economical earthquake resistant design of cable-stayed bridge tower, the use of energy dissipation systems for the earthquake protection of steel structures represents an alternative seismic design method where the tower structure could be constructed to dissipate a large amount of earthquake input energy through inelastic deformations in certain positions, which could be easily retrofitted after damage. The design of energy dissipation systems for bridges could be achieved as the result of two conflicting requirements: no damage under serviceability limit state load condition and maximum dissipation under ultimate limit state load condition. A new concept for cable-stayed bridge tower seismic design that incorporates sacrificial link scheme of low yield point steel horizontal beam is introduced to enable the tower frame structure to remain elastic under large seismic excitation. A nonlinear dynamic analysis for the tower model with the proposed energy dissipation systems is carried out and compared to the response obtained for the tower with its original configuration. The improvement in seismic performance of the tower with supplemental passive energy dissipation system has been measured in terms of the reduction achieved in different response quantities. Obtained results show that the proposed energy dissipation system of low yield point steel seismic link could strongly enhance the seismic performance of the tower structure where the tower and the overall bridge demands are significantly reduced. Low yield point steel seismic link effectively reduces the damage of main structural members under earthquake loading as seismic link yield level decreases due their exceptional behavior as well as its ability to undergo early plastic deformations achieving the concentration of inelastic deformation at tower horizontal beam.