• Title/Summary/Keyword: seismic gap

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Relationship between Olivine Fabrics and Seismic Anisotropy in the Yugu Peridotites, Gyeonggi Massif, South Korea (경기육괴 유구 페리도타이트의 감람석 미구조와 지진파 비등방성의 관계)

  • Munjae Park
    • Economic and Environmental Geology
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    • v.57 no.2
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    • pp.253-261
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    • 2024
  • Olivine, a major mineral in the upper mantle with strong intrinsic elastic anisotropy, plays a crucial role in seismic anisotropy in the mantle, primarily through its lattice preferred orientation (LPO). Despite this, the influence of the microstructure of mylonitic rocks on seismic anisotropy remains inadequately understood. Notably, there is a current research gap concerning seismic anisotropy directly inferred from mylonitic peridotite massifs in Korea. In this study, we introduce the deformation microstructure and LPO of olivine in the mantle shear zone. We calculate the characteristics of seismic anisotropy based on the degree of deformation (proto-mylonite, mylonite, ultra-mylonite) and establish correlations between these characteristics. Our findings reveal that the seismic anisotropy resulting from the olivine LPO in the ultra-mylonitic rock appears to be the weakest, whereas the seismic anisotropy resulting from the olivine LPO in the proto-mylonitic rock appears to be the strongest. The results demonstrate a gradual decrease in seismic anisotropy as the fabric strength (J-index) of olivine LPO diminishes, irrespective of the specific pattern of olivine's LPO. Moreover, all samples exhibit a polarization direction of the fast S-wave aligned subparallel to the lineation. This suggests that seismic anisotropy originating from olivine in mylonitic peridotites is primarily influenced by fabric strength rather than LPO type. Considering these distinctive characteristics of seismic anisotropy is expected to facilitate comparisons and interpretations of the internal mantle structure and seismic data in the Yugu area, Gyeonggi Massif.

Ductility Demand of Precast Coupled Shear Wall (프리캐스트 병렬 전단벽의 연성도 해석)

  • 홍성걸;김영욱
    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.2
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    • pp.29-40
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    • 1999
  • This study presents a simplifled calculation method for required ductility of coupling beams in precast coupled shear walls at preliminary seismic design stages. Deflection of precast coupled shear walls based on a continuum approach is combined with inelastic gap opening of horizontal connection of panels to provide a relationship between the system-level ductility and the element-level ductility in a precast coupled shear wall. The equation proposed herein for ductility requirement for coupling beams shows that higher stiffness and lower strength of coupling beams result in high ductility reuqirement. The equation also shows that the ductility requirement is proportional to the degree of gap opening of the story in question. However, the coupling beam ductility in higher stories are not affected by gap openings of horizontal connections of panel.

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Hysteretic model of isolator gap damper system and its equivalent linearization for random earthquake response analysis

  • Zhang, Hongmei;Gu, Chen
    • Smart Structures and Systems
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    • v.29 no.3
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    • pp.485-498
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    • 2022
  • In near-fault earthquake prone areas, the velocity pulse-like seismic waves often results in excessive horizontal displacement for structures, which may result in severe structural failure during large or near-fault earthquakes. The recently developed isolator-gap damper (IGD) systems provide a solution for the large horizontal displacement of long period base-isolated structures. However, the hysteresis characteristics of the IGD system are significantly different from the traditional hysteretic behavior. At present, the hysteretic behavior is difficult to be reflected in the structural analysis and performance evaluation especially under random earthquake excitations for lacking of effective analysis models which prevent the application of this kind of IGD system. In this paper, we propose a mathematical hysteretic model for the IGD system that presents its nonlinear hysteretic characteristics. The equivalent linearization is conducted on this nonlinear model, which requires the variances of the IGD responses. The covariance matrix for the responses of the structure and the IGD system is obtained for random earthquake excitations represented by the Kanai-Tajimi spectrum by solving the Lyapunov equation. The responses obtained by the equivalent linearization are verified in comparison with the nonlinear responses by the Monte Carlo simulation (MCS) analysis for random earthquake excitations.

Analysis of Seismic Performance of Modular Containment Structure for Small Modular Reactor (소형 원자로용 모듈화 격납구조의 내진성능 분석)

  • Park, Woo-Ryong;Yhim, Sung-Soon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.1
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    • pp.409-416
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    • 2020
  • The seismic performance of a containment structure should be secured to maintain the structural soundness of a containment structure under various earthquakes that occur globally. Therefore, an analysis of the seismic performance of a modular containment structure for a small modular reactor is also required. To analyze the seismic performance of modular containment, FEM models with contact surfaces between the modules and tendon were prepared and the modal and seismic analyses were performed. The displacement, stress, and gap size of modular containment under earthquake wave were analyzed. The effects of the tendon force, friction coefficient, and earthquake wave on the seismic performance were analyzed. The seismic performance of monolithic containment was also analyzed for comparison. In the 1st and 2nd natural modes, which most likely affect, the modular containment showed horizontal dynamic behavior, which is similar to monolithic containment, because of the combined effects of the tendon force and friction force between modules. When the combined effect is sufficient, the seismic performance of the modular containment is secured over a certain level. An additional increase in seismic performance is expected when some material with a larger friction coefficient is adopted on the contact surface.

A new equation based on PGA to provide sufficient separation distance between two irregular buildings in plan

  • Loghmani, Adel;Mortezaei, Alireza;Hemmati, Ali
    • Earthquakes and Structures
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    • v.18 no.5
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    • pp.543-553
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    • 2020
  • Past earthquakes experience shows that serious damage or collapse of buildings have dramatically accrued when sufficient separation distance has not been provided between two adjacent structures. The majority of past studies related to the pounding topic indicate that obtaining the gap size between two buildings is able to prevent collision and impact hazards during seismic excitations. Considering minimization of building collisions, some relationships have been suggested to determine the separation distance between adjacent buildings. Commonly, peak lateral displacement, fundamental period and natural damping as well as structural height of two adjacent buildings are numerically considered to determine the critical distance. Hence, the aim of present study is to focus on all mentioned parameters and also utilizing the main characteristic of earthquake record i.e. PGA to examine the lateral displacement of irregular structures close to each other and also estimate the sufficient separation distance between them. Increasing and decreasing the separation distance is inherently caused economical problems due to the land ownership from a legal perspective and pounding hazard as well. Therefore, a new equation is proposed to determine the optimum critical distance. The accuracy of the proposed formula is validated by different models and various earthquake records.

Hysteretic performance of the all-steel buckling-restrained brace with LY315 steel core

  • Wei, Xuan;Yang, Lu;Chen, Yohchia Frank;Wang, Meng
    • Steel and Composite Structures
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    • v.44 no.6
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    • pp.899-912
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    • 2022
  • To study the seismic performance of the all-steel buckling-restrained brace (BRB) using the novel soft steel LY315 for core member, a total of three identical BRBs were designed and a series of experimental and numerical studies were conducted. First, monotonic and cyclic loading tests were carried out to obtain the mechanical properties of LY315 steel. In addition, the parameters of the Chaboche model were calibrated based on the test results and then verified using ABAQUS. Second, three BRB specimens were tested under cyclic loads to investigate the seismic performance. The failure modes of all the specimens were identified and discussed. The test results indicate that the BRBs exhibit excellent energy dissipation capacity, good ductility, and excellent low-cycle fatigue performance. Then, a finite element (FE) model was established and verified with the test results. Furthermore, a parametric study was performed to further investigate the effects of gap size, restraining ratio, slenderness ratio of the yielding segment, and material properties of the core member on the load capacity and energy dissipation capacity of BRBs.

Enhancing ductility in carbon fiber reinforced polymer concrete sections: A multi-scale investigation

  • Moab Maidi;Gili Lifshitz Sherzer;Erez Gal
    • Computers and Concrete
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    • v.33 no.4
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    • pp.385-398
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    • 2024
  • As concrete dominates the construction industry, alternatives to traditionally used steel reinforcement are being sought. This study explored the suitability of carbon fiber-reinforced polymer (CFRP) as a substitute within rigid frames, focusing on its impact on section ductility and overall structural durability against seismic events. However, current design guidelines address quasi-static loads, leaving a gap for dynamic or extreme circumstances. Our approach included multiscale simulations, parametric study, and energy dissipation analyses, drawing upon a unique adaptation of modified compression field theory. In our efforts to optimize macro and microparameters to improve yield strength, manage brittleness, and govern failure modes, we also recognized the potential of CFRP's high corrosion resistance. This characteristic of CFRP could significantly reduce the frequency of required repairs, thereby contributing to enhanced durability of the structures. The research reveals that CFRP's durability and seismic resistance are attributed to plastic joints within compressed fibers. Notably, CFRP can impart ductility to structural designs, effectively balancing its inherent brittleness, particularly when integrated with quasi-brittle materials. This research challenges the notion that designing bendable components with carbon fiber reinforcement is impractical. It shows that creating ductile bending components with CFRP in concrete is feasible despite the material's brittleness. This funding overturns conventional assumptions and opens new avenues for using CFRP in structural applications where ductility and resilience are crucial.

Review of Seismic Analysis Method for Free Standing High Density Spent Fuel Racks of PWR Plant (가압경수형 발전소 자립형 고밀도 핵연료 저장랙의 지진해석 방법에 대한 검토)

  • 신태명;김범식;손갑헌
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1994.10a
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    • pp.183-190
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    • 1994
  • The paper provides a review of the analysis methods currently being used to perform seismic analysis of free standing high density spent fuel storage racks for PWR. On the basis of the analysis techniques obtained by KAERI from the design experience of Yonggwang unit 3&4 and Ulchin unit 3&4, the analysis procedure and modeling methods are discussed. The analysis of free standing fuel racks requires consideration of complex phenomena such as hydrodynamic coupling, impact through gap between fuel assembly and poison box and racks, frictional effect, rigid body sliding and tipping and etc. The present modeling of these factors is reviewed in comparison with the recommendation of regulatory group. Further improvement of analysis method and the current issues for the development are discussed.

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Circumferential Confinement Effect on Lap-Spliced Reinforcements of Circular Bridge Pier (횡방향 구속이 교각의 겹침이음에 미치는 영향에 대한 고찰)

  • 최영민;황윤국;권태규;박경훈
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.339-342
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    • 2003
  • The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to deterioration of the lap-spliced longitudinal reinforcements without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP wrapping showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by quasi-static experiments.

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Circumferential Confinement Effect of Circular Bridge Pier with FRP Wrapping in Earthquake (지진발생시 FRP 보강이 횡방향 구속에 미치는 효과)

  • 최영민;황윤국;권태규;윤순종
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.09a
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    • pp.280-287
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    • 2003
  • The bridge columns with lap-splice reinforcements in earthquake suffered a brittle bond-slip failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or ductility. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP wrapping. The retrofitted columns using FRP laminated circular tube showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the circumferential confinement effect of existing circular bridge pier strengthened with FRP wrapping for poor lap-splice details. The effects on the confinement of FRP wrapping, such as gap lengths between footing and FRP, fiber orientations, and thicknesses of FRP, were investigated by Quasi-static experiments.

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