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  • Title/Summary/Keyword: seismic inelastic response

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Investigation on Response Modification Factor of RC Structural Walls in Apartment Buildings (아파트 건물의 구조 벽체에 대한 반응수정계수)

  • 한상환;오영훈;이리형
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.544-552
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    • 2001
  • Korea is classified into low and moderate seismic zone from the view-point of seismic hazard level. Korean seismic provisions has been developed based on UBC and ATC 3-06. Thus, in calculation of design base shear according to Korean provisions response modification factor (R) is included in the formula of design base shear. The major role of this factor is to reduce the elastic design base shear whereby structures can behave in inelastic range during design level earthquake ground motions(mean return period of 475 yrs.). R factor is assigned according to material and structural systems. In this study, R factor for bearing wall system is considered. Most of the walls of apartment buildings in Korea resist gravity and seismic loads simultaneously so that this wall system can be classified into bearing wall system. Structural details of these walls are different from those used in Japan and U.S.. They are all rectangular in sectional shape rather than barbell in shape, and also have special lateral reinforcement details at the boundaries of a wall. In Korean seismic design provisions(1988), two different values(3.0 and 3.5) of R factor are assigned to the bearing wall systems according to the wall details. However, in updated seismic provisions(2000), only one value is assigned to R factor(3.0) irrespective of wall details. In this study, the design base shear values in Korean seismic design provisions(1988, 2000), ATC 3-06, UBC are compared. Also experimental study was carried out to evaluate the seismic performance of structural walls. For this purpose, five test specimens were made which have special details used in apartment bearing wall systems in Korea. Based on the results of this study, response modification factor for bearing wall system is discussed.

Component fragility assessment of a long, curved multi-frame bridge: Uniform excitation versus spatially correlated ground motions

  • Jeon, Jong-Su;Shafieezadeh, Abdollah;DesRoches, Reginald
    • Structural Engineering and Mechanics
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    • v.65 no.5
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    • pp.633-644
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    • 2018
  • This paper presents the results of an assessment of the seismic fragility of a long, curved multi-frame bridge under multi-support earthquake excitations. To achieve this aim, the numerical model of columns retrofitted with elliptical steel jackets was developed and validated using existing experimental results. A detailed nonlinear numerical model of the bridge that can capture the inelastic response of various components was then created. Using nonlinear time-history analyses for a set of stochastically generated spatially variable ground motions, component demands were derived and then convolved with new capacity-based limit state models to obtain seismic fragility curves. The comparison of failure probabilities obtained from uniform and multi-support excitation analyses revealed that the consideration of spatial variability significantly reduced the median value of fragility curves for most components except for the abutments. This observation indicates that the assumption of uniform motions may considerably underestimate seismic demands. Moreover, the spatial correlation of ground motions resulted in reduced dispersion of demand models that consequently decreased the dispersion of fragility curves for all components. Therefore, the spatial variability of ground motions needs to be considered for reliable assessment of the seismic performance of long multi-frame bridge structures.

Quasi-Static Test for Seismic Performance of Reinforced Concrete Bridge Piers with Lap Splice (준정적실험에 의한 실물 원형교각의 내진성능평가를 위한 실험적 연구)

  • Kim, Hoon;Chung, Young-Soo;Lee, Jae-Hoon;Choi, Jin-Ho;Cho, Jun-Sang
    • Proceedings of the Korea Concrete Institute Conference
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    • 2002.05a
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    • pp.941-946
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    • 2002
  • Short reinforced concrete bridge piers are particularly susceptible to shear failure as a consequence of the high shear/moment ratio and conservatism in the flexural strength design of existing RC bridge pier, which were constructed before 1992. In addition, shear failure is brittle and involves rapid strength degradation. Inelastic shear deformation is thus unsuitable for ductile seismic response. It is, however, believed that there are not many experimental research works for shear failure of the existing RC bridge pier in Korean peninsula subjected to earthquake motions. The object of this research is to evaluate the seismic performance of existing circular RC bridge piers by the quasi-static test. Existing RC bridge piers were moderate seismically designed in accordance with the conventional provisions of Korea Highway Design Specification. This study has been performed to verify the effect of aspect ratio (column height-diameter ratio). Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as lateral force-displacement hysteric curve, envelope curve etc.

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Seismic behavior of frames with innovative energy dissipation systems (FUSEIS 1-1)

  • Dougka, Georgia;Dimakogianni, Danai;Vayas, Ioannis
    • Earthquakes and Structures
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    • v.6 no.5
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    • pp.561-580
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    • 2014
  • After strong earthquakes conventional frames used worldwide in multi - story steel buildings (e.g. moment resisting frames) are not well positioned according to reparability. Two innovative systems for seismic resistant steel frames incorporated with dissipative fuses were developed within the European Research Program "FUSEIS" (Vayas et al. 2013). The first, FUSEIS1, resembles a vertical Vierendeel beam and is composed of two closely spaced strong columns rigidly connected to multiple beams. In the second system, FUSEIS2, a discontinuity is introduced in the composite beams of a moment resisting frame and the dissipative devices are steel plates connecting the two parts. The FUSEIS system is able to dissipate energy by means of inelastic deformations in the fuses and combines ductility and architectural transparency with stiffness. In case of strong earthquakes damage concentrates only in the fuses which behave as self-centering systems able to return the structure to its initial undeformed shape. Repair work after such an event is limited only to replacing the fuses. Experimental and numerical investigations were performed to study the response of the fuses system. Code relevant design rules for the seismic design of frames with dissipative FUSEIS and practical recommendations on the selection of the appropriate fuses as a function of the most important parameters and member verifications have been formulated and are included in a Design Guide. This article presents the design and performance of building frames with FUSEIS 1-1 based on models calibrated on the experimental results.

Response of the structures excited by the near fault ground motion (Near Fault Ground Motion에 의한 구조물의 거동 특성 연구)

  • Kim, Jae-Kwan;Kim, Jung-Han
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2005.03a
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    • pp.42-46
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    • 2005
  • Ground motions with the near fault effects are studied for the seismic design and the analysis of structures. The characteristics of the velocity pulse by the forward directivity are studied and the relations between velocity pulse and earthquake magnitude are investigated. The elastic response spectra of the near fault ground motion are compared with these of the far fault ground motion. And effects on the behaviors of structures are studied by the analysis of the elastic and the inelastic single degree of freedom system in terms of the response spectrum and the ductility demand.

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Inelastic Behavior of Steel Frames with Buckling Restrained Braced (비좌굴가새가 설치된 골조의 비탄성거동)

  • Kim Jin-Koo;Park Jun-Hee
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2005.04a
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    • pp.97-104
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    • 2005
  • The seismic behavior of framed structure with Chevron-type bucking restrained braces were investigated and their behavior factors were evaluated following the procedure proposed in ATC-19 & ATC-34. Two types of structures, building frame systems and dual systems, with 4, 8, 12, and 16 stories were designed per the IBC 2000, the AISC LRFD and the AISC/SEAOC Recommended Provisions for BRBF. Nonlinear static pushover analyses were carried out to observe the plastic hinge formation and to identify the loads and the displacements at the yield and the ultimate states. Time history analyses were also carried out to compute the permanent displacement md the dissipated hysteretic energy. According to the analysis results, the response modification factors of model structures fumed out to be larger than what is proposed in the provision in low story structures, and a little smaller in medium-story structures. The dual systems, even though designed with smaller seismic load, showed superior static and dynamic performances.

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Fatigue Damage Assessment for Steel Structures Subjected to Earthquake (지진에 대한 강구조물의 피로손상도 추정법)

  • Song, Jong Keol;Yun, Chung Bang;Lee, Dong Guen
    • Journal of Korean Society of Steel Construction
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    • v.9 no.1 s.30
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    • pp.95-105
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    • 1997
  • Structures subjected to strong seismic excitation may undergo inelastic deformation cycles. The resulting cumulative fatigue damage process reduces the ability of structures and components to withstand seismic loads. Yet, the present earthquake resistance design methods focus mainly on the maximum displacement ductility, ignoring the effect of the cyclic responses. The damage parameters closely related to the cumulative damage need to be properly reflected on the aseismic design methods. In this study, two cumulative damage assessment methods derived from the plastic fatigue theory are investigated. The one is based on the hysteretic ductility amplitude, and the other is based on the dissipated hysteretic energy. Both methods can consider the maximum ductility and the cyclic behavior of structural response. The validity of two damage methods has been examined for single degree of freedom structures with various natural frequencies against two different earthquake excitations.

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Evaluation of Nonlinear Dynamic Behavior for Steel Moment Frame Structures Considering P-Δ Effects (P-Δ 효과를 고려한 철골 구조물의 비선형 동적거동 평가)

  • 최원호;이주완;이동근
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.09a
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    • pp.235-242
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    • 2001
  • Inelastic seismic response of steel moment frame structures, which are usually quite gravity load and subject to large displacement under severe earthquake, may be severly influenced by the structure P-Δ effects. The P-Δ effect may have an important impact on the dynamic behavior of the structure in the nonlinear seismic analysis. In multi degree of freedom systems P-Δ effects may significantly affect only a subset of stories or a single story alone. Therefore, a story drift amplification of structure is happened by P-Δeffects and such nonlinear dynamic behaviors are very difficult to evaluate in the structures. In this study, two systems having different design methods of steel moment frame structures are investigated to evaluate the P-Δ effects due to gravity load. The plastic hinge formations, maximum rotational ductility demands, and energy distribution will be compared and evaluated following whether the P-Δ effects are considered or not. And design methods are proposed for the prevention of the instability of structures which due to the P-Δ effects.

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Design Eccentricity in Equivalent Seismic Load Using Modal Analysis (모드 해석을 이용한 등가 지진하중에서의 설계 편심)

  • 조소훈;이명규
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.09a
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    • pp.268-275
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    • 2001
  • Modal analysis does well predict the elastic dynamic response of the torsionally unbalanced structure. But modal analysis overestimates the rotation of the structure in inelastic range, so one side members require ductility too much and the others require ductility too small in comparison with torsionally balanced structure. In this paper, in order to reduce difference of ductility demand between both side members of the torsionally unbalanced structure, design eccentricity of seismic load is evaluated and the method determining the strength center of structure is proposed using modal analysis. For several cases, the ductility demand of stucture is compared to investigate the propriety of the proposed approach.

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A preliminary case study of resilience and performance of rehabilitated buildings subjected to earthquakes

  • Hadigheh, S. Ali;Mahini, S. Saeed;Setunge, Sujeeva;Mahin, Stephen A.
    • Earthquakes and Structures
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    • v.11 no.6
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    • pp.967-982
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    • 2016
  • Current codes design the buildings based on life safety criteria. In a performance-based design (PBD) approach, decisions are made based on demands, such as target displacement and performance of structure in use. This type of design prevents loss of life but does not limit damages or maintain functionality. As a newly developed method, resilience-based design (RBD) aims to maintain functionality of buildings and provide liveable conditions after strong ground movement. In this paper, the seismic performance of plain and strengthened RC frames (an eight-story and two low-rise) is evaluated. In order to evaluate earthquake performance of the frames, the performance points of the frames are calculated by the capacity spectrum method (CSM) of ATC-40. This method estimates earthquake-induced deformation of an inelastic system using a reduced response spectrum. Finally, the seismic performances of the frames are evaluated and the results are compared with a resilience-based design criterion.