• Title/Summary/Keyword: Earthquake Experience

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Plastic Deformation Capacity of Steel Beam-to-Column Connection under Long-duration Earthquake

  • Yamada, Satoshi;Jiao, Yu;Narihara, Hiroyuki;Yasuda, Satoshi;Hasegawa, Takashi
    • International Journal of High-Rise Buildings
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    • v.3 no.3
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    • pp.231-241
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    • 2014
  • Ductile fracture is one of the most common failure modes of steel beam-to-column connections in moment resisting frames. Most proposed evaluation methods of the plastic deformation capacity of a beam until ductile fracture are based on steel beam tests, where the material's yield strength/ratio, the beam's moment gradient, and loading history are the most important parameters. It is impossible and unpractical to cover all these parameters in real tests. Therefore, a new attempt to evaluate a beam's plastic deformation capacity through analysis is introduced in this paper. Another important issue is about the loading histories. Recent years, the effect on the structural component under long-duration ground motion has drawn great attentions. Steel beams tends to experience a large number of loading cycles with small amplitudes during long-duration earthquakes. However, current research often focuses on the beam's behavior under standard incremental loading protocols recommended by respective countries. In this paper, the plastic deformation capacity of steel beams subjected to long duration ground motions was evaluated through analytical methodology.

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.

A Study on the Probabilistic Safety Assessment and Sensitivity Analysis of Success Criteria of Large LOCA for APR+ (APR+ 확률론적 안전성평가 및 대형냉각재상실사고 성공기준과 파단크기 민감도 분석)

  • Moon, Horim;Kim, Han Gon
    • Journal of the Korean Society of Safety
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    • v.31 no.6
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    • pp.129-134
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    • 2016
  • Standard design of APR+(advanced power reactor plus) was certified at 2014 by Korea regulatory body. Based on the experience gained from OPR1000 and APR1400, the APR1400 was being developed as a 1,500MWe class reactor using Korean technologies for design code, reactor coolant pump, and man-machine interface system. APR+ has been basically designed to have the seismic design basis of safe shutdown earthquake (SSE) 0.3g, a 4-train safety concept based on N+2 design philosophy, and a passive auxiliary feedwater system (PAFS). Also, safety issues on the Fukushima-type accidents have been extensively reviewed and applied to enhance APR+ safety. APR+ provides higher reliability and safety against tsunami and earthquake. The purpose of this paper is to implement probabilistic safety assessment considering these design features and to analyze sensitivity of core damage frequency for large loss of coolant accident of APR+.

A new damage index for reinforced concrete structures

  • Cao, Vui V.;Ronagh, Hamid R.;Ashraf, Mahmud;Baji, Hassan
    • Earthquakes and Structures
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    • v.6 no.6
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    • pp.581-609
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    • 2014
  • Reinforced concrete (RC) structures are likely to experience damage when subjected to earthquakes. Damage index (DI) has been recognised as an advanced tool of quantitatively expressing the extent of damage in such structures. Last 30 years have seen many concepts for DI proposed in order to calibrate the observed levels of damage. The current research briefly reviews all available concepts and investigates their relative merits and limitations with a view to proposing a new concept based on residual deformation. Currently available DIs are classified into two broad categories - non-cumulative DI and cumulative DI. Non-cumulative DIs do not include the effects of cyclic loading, whilst the cumulative concepts produce more rational indication of the level of damage in case of earthquake excitations. Ideally, a DI should vary within a scale of 0 to 1 with 0 representing the state of elastic response, and 1 referring to the state of total collapse. Some of the available DIs do not satisfy these criteria. A new DI based on energy is proposed herein and its performances, both for static and for cyclic loadings, are compared with those obtained using the most widely accepted DI in literature. The proposed DI demonstrates a rational way to predict the extent of damage for a number of case studies. More research is encouraged to address some identified issues.

Response of Skew Bridges with permutations of geometric parameters and bearings articulation

  • Fakhry, Mina F.;ElSayed, Mostafa M.;Mehanny, Sameh S.F.
    • Earthquakes and Structures
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    • v.17 no.5
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    • pp.477-487
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    • 2019
  • Understanding the behavior of skew bridges under the action of earthquakes is quite challenging due to the combined transverse and longitudinal responses even under unidirectional hit. The main goal of this research is to assess the response of skew bridges when subjected to longitudinal and transversal earthquake loading. The effect of skew on the response considering two- and three- span bridges with skew angles varying from 0 to 60 degrees is illustrated. Various pier fixities (and hence stiffness) and cross-section shapes, as well as different abutment's bearing articulations, are also studied. Finite-element models are established for modal and seismic analyses. Around 900 models are analyzed under the action of the code design response spectrum. $Vis-{\grave{a}}-vis$ modal properties, the higher the skew angle, the less the fundamental period. In addition, it is found that bridges with skew angles less than 30 degrees can be treated as straight bridges for the purpose of calculating modal mass participation factors. Other monitored results are bearings' reactions at abutments, shear and torsion demand in piers, as well as deck longitudinal displacement. Unlike straight bridges, it has been typically noted that skew bridges experience non-negligible torsion and bi-directional pier base shears. In a complementary effort to assess the accuracy of the conducted response spectrum analysis, a series of time-history analyses are applied under seven actual earthquake records scaled to match the code design response spectrum and critical comparisons are performed.

Simulation of cyclic response of precast concrete beam-column joints

  • Adibi, Mahdi;Talebkhah, Roozbeh;Yahyaabadi, Aliakbar
    • Computers and Concrete
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    • v.24 no.3
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    • pp.223-236
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    • 2019
  • Experience of previous earthquakes shows that a considerable portion of concrete precast buildings sustain relatively large damages especially at the beam-column joints where the damages are mostly caused by bar slippage. Precast concrete buildings have a kind of discontinuity in their beam-column joints, so reinforcement details in this area is too important and have a significant effect on the seismic behavior of these structures. In this study, a relatively simple and efficient nonlinear model is proposed to simulate pre- and post-elastic behavior of the joints in usual practice of precast concrete building. In this model, beam and column components are represented by linear elastic elements, dimensions of the joint panel are defined by rigid elements, and effect of slip is taken into account by a nonlinear rotational spring at the end of the beam. The proposed method is validated by experimental results for both internal and external joints. In addition, the seismic behavior of the precast building damaged during Bojnord earthquake 13 May 2017, is investigated by using the proposed model for the beam-column joints. Damage unexpectedly inducing the precast building in the moderate Bojnord earthquake may confirm that bearing capacity of the precast building was underestimated without consideration of joint behavior effect.

Vertical uplift of suspension equipment due to hanger slackening: Experimental and numerical investigation

  • Yang, Zhenyu;He, Chang;Mosalam, Khalid M.;Xie, Qiang
    • Structural Engineering and Mechanics
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    • v.82 no.6
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    • pp.735-745
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    • 2022
  • The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

An Iterative Scheme for Resolving Unbalanced Forces Between Nonlinear Flexural Bending and Shear Springs in Lumped Plasticity Model (비선형 휨 및 전단 힌지 사이의 불평형력 해소를 위한 수렴계산 기법)

  • Kim, Yousok
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.6
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    • pp.227-235
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    • 2022
  • For a member model in nonlinear structural analysis, a lumped plastic model that idealizes its flexural bending, shear, and axial behaviors by springs with the nonlinear hysteretic model is widely adopted because of its simplicity and transparency compared to the other rigorous finite element methods. On the other hand, a challenging task in its numerical solution is to satisfy the equilibrium condition between nonlinear flexural bending and shear springs connected in series. Since the local forces between flexural and shear springs are not balanced when one or both springs experience stiffness changes (e.g., cracking, yielding, and unloading), the additional unbalanced force due to overshooting or undershooting each spring force is also generated. This paper introduces an iterative scheme for numerical solutions satisfying the equilibrium conditions between flexural bending and shear springs. The effect of equilibrium iteration on analysis results is shown by comparing the results obtained from the proposed method to those from the conventional scheme, where the equilibrium condition is not perfectly satisfied.

A parametric investigation on seismic performance of ageing Sarıyar dam

  • Ahmad Yamin Rasa;Ahmet Budak
    • Structural Engineering and Mechanics
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    • v.91 no.2
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    • pp.123-133
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    • 2024
  • The assessment of seismic behavior and seismic performance of ageing Sarıyar concrete gravity dam constructed on Sakarya River in Türkiye is the main focus of this paper. For this purpose, the impact of sediment domain, ageing of concrete material under the impact of chemical and mechanical actions, and dam-water-sediment interaction are included in the two-dimensional (2D) finite element (FE) model developed in FORTRAN 90 environment. In the FE model, the dam and age dependent sediment domains are modeled by solid elements, while reservoir domain is modeled by Lagrangian fluid elements. The radiation of reflected waves to the unbounded water domain is modeled by infinite Lagrangian fluid elements, while unbounded sediment domain is modeled by infinite solid elements. The coupled system was assumed to be under the simultaneous impact of Vertical (V) and Horizontal (H) ingredients of 1976 Koyna earthquake and the coupled system was analyzed in Laplace domain by direct method. Due to the deterioration of the concrete, the H and V displacement responses together with the fundamental period of the body, elongate throughout the lifetime and this reduce the seismic safety of the dam. It was deduced that the ageing dam body will not experience major damages under the Koyna earthquake both at the earlier and later ages. Furthermore, at the heel of the dam, the hydrodynamic pressure responses are decreased by rising the sediment domain depth.

Authenticity in Dark Tourism : A Case of Disaster Tourism after the Great East Japan Earthquake (다크투어리즘과 관광경험의 진정성 - 동일본대지진의 재난관광을 사례로 -)

  • Cho, Ara
    • Journal of the Korean association of regional geographers
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    • v.19 no.1
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    • pp.130-146
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    • 2013
  • This study aimed to analyze the authenticity of dark tourism, and to discuss the possibilities and limitations of disaster tourism as an alternative type of tourism in post-modern society. For this purpose, disaster tourism related with the Great East Japan Earthquake was analyzed. After the disaster occurred, the boundaries between guests (tourists) and hosts (residents) dissolved and disaster communities emerged temporarily. This was followed by social contributive tourism, in which both guests and hosts shared their matter of life-and-death experiences, so existential authenticity became the most important motive and experience for tourism. As time passed, however, existential authenticity was reconstructed ideologically in the socioeconomic political context of disaster recovery, and replaced constructive authenticity. After all, the possibilities of disaster tourism as an alternative type of tourism based on the introspection of modernity were restricted. To discuss the underlying ethical issues of the commodification of disaster tourism, further researches should conducted to consider dark tourism as an alternative type of postmodern tourism.

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