• 제목/요약/키워드: Seismic design code

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Distribution of near-fault input energy over the height of RC frame structures and its formulation

  • Taner Ucar
    • Structural Engineering and Mechanics
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    • 제85권1호
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    • pp.55-64
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    • 2023
  • Energy-based seismic design and evaluation methods are promising to be involved in the next generation design codes. Accordingly, determining the distribution of earthquake input energy demand among floor levels is quite imperative in order to develop an energy-based seismic design procedure. In this paper, peak floor input energy demands are achieved from relative input energy response histories of several reinforced concrete (RC) frames. A set of 22 horizontal acceleration histories selected from recorded near-fault earthquakes and scaled in time domain to be compatible with the elastic acceleration design spectra of Turkish Seismic Design Code are used in time history analyses. The distribution of the computed input energy per mass values and the arithmetic means through the height of the considered RC frames are presented as a result. It is found that spatial distribution of input energy per mass is highly affected by the number of stories. Very practical yet consistent formulation of distributing the total input energy to story levels is achieved, as a most important contribution of the study.

INTEGRITY ANALYSIS OF AN UPPER GUIDE STRUCTURE FLANGE

  • LEE, KI-HYOUNG;KANG, SUNG-SIK;JHUNG, MYUNG JO
    • Nuclear Engineering and Technology
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    • 제47권6호
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    • pp.766-775
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    • 2015
  • The integrity assessment of reactor vessel internals should be conducted in the design process to secure the safety of nuclear power plants. Various loads such as self-weight, seismic load, flow-induced load, and preload are applied to the internals. Therefore, the American Society of Mechanical Engineers (ASME) Code, Section III, defines the stress limit for reactor vessel internals. The present study focused on structural response analyses of the upper guide structure upper flange. The distributions of the stress intensity in the flange body were analyzed under various design load cases during normal operation. The allowable stress intensities along the expected sections of stress concentration were derived from the results of the finite element analysis for evaluating the structural integrity of the flange design. Furthermore, seismic analyses of the upper flange were performed to identify dynamic behavior with respect to the seismic and impact input. The mode superposition and full transient methods were used to perform time-history analyses, and the displacement at the lower end of the flange was obtained. The effect of the damping ratio on the response of the flange was also evaluated, and the acceleration was obtained. The results of elastic and seismic analyses in this study will be used as basic information to judge whether a flange design meets the acceptance criteria.

A comparison of three performance-based seismic design methods for plane steel braced frames

  • Kalapodis, Nicos A.;Papagiannopoulos, George A.;Beskos, Dimitri E.
    • Earthquakes and Structures
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    • 제18권1호
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    • pp.27-44
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    • 2020
  • This work presents a comparison of three performance-based seismic design methods (PBSD) as applied to plane steel frames having eccentric braces (EBFs) and buckling restrained braces (BRBFs). The first method uses equivalent modal damping ratios (ξk), referring to an equivalent multi-degree-of-freedom (MDOF) linear system, which retains the mass, the elastic stiffness and responds in the same way as the original non-linear MDOF system. The second method employs modal strength reduction factors (${\bar{q}}_k$) resulting from the corresponding modal damping ratios. Contrary to the behavior factors of code based design methods, both ξk and ${\bar{q}}_k$ account for the first few modes of significance and incorporate target deformation metrics like inter-storey drift ratio (IDR) and local ductility as well as structural characteristics like structural natural period, and soil types. Explicit empirical expressions of ξk and ${\bar{q}}_k$, recently presented by the present authors elsewhere, are also provided here for reasons of completeness and easy reference. The third method, developed here by the authors, is based on a hybrid force/displacement (HFD) seismic design scheme, since it combines the force-base design (FBD) method with the displacement-based design (DBD) method. According to this method, seismic design is accomplished by using a behavior factor (qh), empirically expressed in terms of the global ductility of the frame, which takes into account both non-structural and structural deformation metrics. These expressions for qh are obtained through extensive parametric studies involving non-linear dynamic analysis (NLDA) of 98 frames, subjected to 100 far-fault ground motions that correspond to four soil types of Eurocode 8. Furthermore, these factors can be used in conjunction with an elastic acceleration design spectrum for seismic design purposes. Finally, a comparison among the above three seismic design methods and the Eurocode 8 method is conducted with the aid of non-linear dynamic analyses via representative numerical examples, involving plane steel EBFs and BRBFs.

완화된 배근 상세를 갖는 병렬전단벽 구조시스템의 내진성능평가 (Seismic Performance of Coupled Shear Wall Structural System with Relaxed Reinforcement Details)

  • 송정원;천영수;송진규;서수연;양근혁
    • 콘크리트학회논문집
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    • 제28권2호
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    • pp.187-196
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    • 2016
  • KBC2009에 의하면 특수전단벽과 연결되는 폭이 좁고 춤이 높은 연결보는 대각선 다발철근 보강을 실시해야 한다. 그러나 대각선 다발 철근의 사용은 시공성과 경제성에 부정적인 영향을 미칠 것으로 예상된다. 이에 본 연구에서는 4개의 서로 다른 상세를 갖는 연결보를 대상으로 주기하중 재하 실험을 실시하여 각각의 성능을 평가하였다. 또한 그 실험결과를 바탕으로 하여 특수전단벽과 연결보로 이루어진 병렬전단벽 구조시스템을 구성하여 FEMA P695에 따른 방법론으로 내진성능평가를 실시하였다.

Seismic retrofitting by base-isolation of r.c. framed buildings exposed to different fire scenarios

  • Mazza, Fabio;Mazza, Mirko
    • Earthquakes and Structures
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    • 제13권3호
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    • pp.267-277
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    • 2017
  • Base-isolation is now being adopted as a retrofitting strategy to improve seismic behaviour of reinforced concrete (r.c.) framed structures subjected to far-fault earthquakes. However, the increase in deformability of a base-isolated framed building may lead to amplification in the structural response under the long-duration horizontal pulses of high-magnitude near-fault earthquakes, which can become critical once the strength level of a fire-weakened r.c. superstructure is reduced. The aim of the present work is to investigate the nonlinear seismic response of fire-damaged r.c. framed structures retrofitted by base-isolation. For this purpose, a five-storey r.c. framed building primarily designed (as fixed-base) in compliance with a former Italian seismic code for a medium-risk zone, is to be retrofitted by the insertion of elastomeric bearings to meet the requirements of the current Italian code in a high-risk seismic zone. The nonlinear seismic response of the original (fixed-base) and retrofitted (base-isolated) test structures in a no fire situation are compared with those in the event of fire in the superstructure, where parametric temperature-time curves are defined at the first level, the first two and the upper levels. A lumped plasticity model describes the inelastic behaviour of the fire-damaged r.c. frame members, while a nonlinear force-displacement law is adopted for the elastomeric bearings. The average root-mean-square deviation of the observed spectrum from the target design spectrum together with a suitable intensity measure are chosen to select and scale near- and far-fault earthquakes on the basis of the design hypotheses adopted.

원형 철근콘크리트 교각의 내진성능 I. 심부구속철근비 영향 변수 평가 (A Seismatic Performance Analysis of Circular RC Bridge Piers I. Evaluation of Influence Parameters of Confinement Steel Ratio)

  • 이대형;박창규;김현준;정영수
    • 콘크리트학회논문집
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    • 제17권4호
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    • pp.603-611
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    • 2005
  • 본 연구에서는 합리적인 내진설계기준의 정립을 위하여 철근콘크리트 교각의 내진성능에 영향을 미치는 주요 인자에 대하여 분석하였다. 주요 각국의 내진규정에서 내진성능을 발휘하기 위한 심부구속철근량을 규정함에 있어 다양한 요소들을 고려하고 있다. 하지만, 이러한 요소들이 합리적으로 고려되었는가에 대해서는 의문이 남는다. 따라서 본 연구에서 국내의 도로교설계기준, Eurocode 8 part2, NZS 3101, ATC-32 등의 설계기준을 비교분석하고, 기존 실험 연구 결과와 비교 분석하여 합리적인 영향인자들을 제안하고자 하였다. 연구결과에 따르면 원형 철근콘크리트 교각의 내진성능에 가장 지배적인 영향인자는 축하중비인 것으로 조사되었다. 따라서 심부구속철근비 산정식에 축하중비의 영향을 전혀 고려하고 있지 않는 현행 도로교설계기준에 축하중비를 도입해야 한다.

Effect of poorly-compacted backfill around embedded foundations on building seismic response

  • Kim, Yong-Seok
    • Earthquakes and Structures
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    • 제3권3_4호
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    • pp.549-561
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    • 2012
  • Many building foundations are embedded, however it is not easy to compact the backfill around the foundation especially for the deeply embedded ones. The soil condition around the embedded foundation may affect the seismic response of a building due to the weak contact between the soil and the foundation. In this paper, the response accelerations in the short-period range and at the period of 1 second (in the long-period range) for a seismic design spectrum specified in the IBC design code were compared considering perfect and poor backfills to investigate the effect of backfill compaction around the embedded foundation. An in-house finite-element software (P3DASS) which has the capability of horizontal pseudo-3D seismic analysis with linear soil layers was used to perform the seismic analyses of the structure-soil system with an embedded foundation. Seismic analyses were carried out with 7 bedrock earthquake records provided by the Pacific Earthquake Engineering Research Center (PEER), scaling the peak ground accelerations to 0.1 g. The results indicate that the poor backfill is not detrimental to the seismic response of a building, if the foundation is not embedded deeply in the soft soil. However, it is necessary to perform the seismic analysis for the structure-soil system embedded deeply in the soft soil to check the seismic resonance due to the soft soil layer beneath the foundation, and to compact the backfill as well as possible.

Seismic performance assessment of R.C. bridge piers designed with the Algerian seismic bridges regulation

  • Kehila, Fouad;Kibboua, Abderrahmane;Bechtoula, Hakim;Remki, Mustapha
    • Earthquakes and Structures
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    • 제15권6호
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    • pp.701-713
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    • 2018
  • Many bridges in Algeria were constructed without taking into account the seismic effect in the design. The implantation of a new regulation code RPOA-2008 requires a higher reinforcement ratio than with the seismic coefficient method, which is a common feature of the existing bridges. For better perception of the performance bridge piers and evaluation of the risk assessment of existing bridges, fragility analysis is an interesting tool to assess the vulnerability study of these structures. This paper presents a comparative performance of bridge piers designed with the seismic coefficient method and the new RPOA-2008. The performances of the designed bridge piers are assessed using thirty ground motion records and incremental dynamic analysis. Fragility curves for the bridge piers are plotted using probabilistic seismic demand model to perform the seismic vulnerability analysis. The impact of changing the reinforcement strength on the seismic behavior of the designed bridge piers is checked by fragility analysis. The fragility results reveal that the probability of damage with the RPOA-2008 is less and perform well comparing to the conventional design pier.

Seismic pounding effects on the adjacent symmetric buildings with eccentric alignment

  • Abdel Raheem, Shehata E.;Fooly, Mohamed Y.M.;Omar, Mohamed;Abdel Zaher, Ahmed K.
    • Earthquakes and Structures
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    • 제16권6호
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    • pp.715-726
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    • 2019
  • Several municipal seismic vulnerability investigations have been identified pounding of adjacent structures as one of the main hazards due to the constrained separation distance between adjacent buildings. Consequently, an assessment of the seismic pounding risk of buildings is superficial in future adjustment of design code provisions for buildings. The seismic lateral oscillation of adjacent buildings with eccentric alignment is partly restrained, and therefore a torsional response demand is induced in the building under earthquake excitation due to eccentric pounding. In this paper, the influence of the eccentric seismic pounding on the design demands for adjacent symmetric buildings with eccentric alignment is presented. A mathematical simulation is formulated to evaluate the eccentric pounding effects on the seismic design demands of adjacent buildings, where the seismic response analysis of adjacent buildings in series during collisions is investigated for various design parameters that include number of stories; in-plan alignment configurations, and then compared with that for no-pounding case. According to the herein outcomes, the effects of seismic pounding severity is mainly depending on characteristics of vibrations of the adjacent buildings and on the characteristics of input ground motions as well. The position of the building wherever exterior or interior alignment also, influences the seismic pounding severity as the effect of exposed direction from one or two sides. The response of acceleration and the shear force demands appear to be greater in case of adjacent buildings as seismic pounding at different levels of stories, than that in case of no-pounding buildings. The results confirm that torsional oscillations due to eccentric pounding play a significant role in the overall pounding-involved response of symmetric buildings under earthquake excitation due to horizontal eccentric alignment.

보라매 대교빌딩 리모델링을 위한 지진응답 저감기술 적용사례 (Application of the Seismic Response Reduction Technology for Boramae Deokyo Building Remodeling)

  • 박영미;박기홍;조성준
    • 한국건축시공학회:학술대회논문집
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    • 한국건축시공학회 2013년도 추계 학술논문 발표대회
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    • pp.134-136
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    • 2013
  • In general, the seismic retrofit is almost essential to extend and remodel aged buildings. Because domestic seismic design code has been enhanced, seismic performance should be secure for aged building remodeling. Seismic response reduction device (damper) is lately appling to ensure seismic performance. This device is economical efficiency method that can reduce the load to foundation and the range of structural reinforcements, shorten of construction period. New shaped steel damper was applied for extension and remodeling construction for Boramae Deakyo building. As a result, the economy and shortening of construction period was achieved.

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