• Title/Summary/Keyword: Interstory drift

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Effectiveness of rocking walls system in seismic retrofit of vertically irregular RC buildings

  • Tadeh Zirakian;Omid Parvizi;Mojtaba Gorji Azandariani;David Boyajian
    • Steel and Composite Structures
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    • v.52 no.5
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    • pp.543-555
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    • 2024
  • This study examines the seismic vulnerability of vertically irregular reinforced concrete (RC) frame buildings, focusing on the effectiveness of retrofitting techniques such as rocking walls (RWs) in mitigating soft story mechanisms. Utilizing a seven-story residential apartment as a prototype in a high-seismicity urban area, this research performs detailed nonlinear simulations to evaluate both regular and irregular structures, both before and after retrofitting. Pushover and nonlinear time history analyses were conducted using OpenSees software, with a suite of nine ground motion records to capture diverse seismic scenarios. The findings indicate that retrofitting with RWs significantly improves seismic performance: for instance, roof displacements at the Collapse Prevention (CP) level decreased by up to 23% in the irregular structure with retrofitting compared to its non-retrofitted counterpart. Additionally, interstory drift ratios were more uniform post-retrofit, with Drift Concentration Factor (DCF) values approaching 1.0 across all performance levels, reflecting reduced variability in seismic response. The global ductility of the retrofitted buildings improved, with displacement ductility ratios increasing by up to 29%. These results underscore the effectiveness of RWs in enhancing global ductility, mitigating soft story failures, and providing a more predictable deformation pattern during seismic events. The study thus provides valuable insights into the robustness and cost-effectiveness of using rocking walls for retrofitting irregular RC buildings.

Inelastic Analysis of Steel Frame Structures with Viscoelastic Damper (점탄성 감쇠기가 설치된 철골조 건물의 비탄성 해석)

  • 김진구
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.04a
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    • pp.186-193
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    • 2000
  • In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load and a ten-story structure subjected to gravity and wind load were designed. the code-specified design spectrums were constructed for each soil type and performance objective and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Interstory drift was adopted as the primary performance criterion. According to the analysis results both model structures turned out to satisfy the life safety performance level for most of the soil conditions except for the soft soil. It was also found that the seismic performance could be greatly enhanced by installing viscoelastic dampers on appropriate locations.

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Seismic Response of Self-Centering Energy Dissipative Braced Frames (셀프센터링 가새골조의 지진응답)

  • Choi, Hyun-Hoon;Christopoulos, C.;Kim, Jin-Koo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.331-336
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    • 2008
  • An self-centering energy-dissipative (SCED) bracing system has recently been developed as a new seismic force resistant bracing system. The advantage of the SCED brace system is that, unlike other comparable advanced bracing systems that dissipate energy, such as the buckling restrained brace system, it has a self-centering capability that reduces or eliminates residual building deformations after major seismic events. In this study seismic performance of SCED braced frames is evaluated for a set of 20 design level earthquake records. According to analysis results the SCED systems showed more uniform interstory drift demand for buildings with 8 story or fewer. The residual deformation in SCED buildings turned out to be much less than that of moment-resisting frames.

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Shaking Table Tests of A 1/12-Scale Reinforced Concrete Upper-Wall Lower-Frame Structure (1/12 축소 철근콘크리트 주상복합구조물의 진동대실험)

  • 이한선;김상연;고동우;권기혁;김병현
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.05a
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    • pp.139-144
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    • 2001
  • The objective of this study is to investigate the behavior of 1/12 scale upper-wall lower-frame reinforced concrete structure subjected to earthquake excitations. For this purpose, Taft N21E earthquake accelerogram was simulated by using 4m$\times$4m shaking table. When the input acceleration is compared to that of output, it was found that simulation of shaking table is satisfactory. From the test results with peak ground acceleration(PGA) 0.22g, which corresponds to 0.11g in prototype by the similitude law, it can be observed that the model responded in elastic behavior and that large interstory drift occurred at the lower part of the structure.

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Developing fragility curves and loss functions for masonry infill walls

  • Cardone, Donatello;Perrone, Giuseppe
    • Earthquakes and Structures
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    • v.9 no.1
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    • pp.257-279
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    • 2015
  • The primary objective of this study is to summarize results from previous experimental tests on laboratory specimens of RC/steel frames with masonry infills, in order to develop fragility functions that permit the estimation of damage in typical non-structural components of RC frame buildings, as a function of attained peak interstory drift. The secondary objective is to derive loss functions for such non-structural components, which provide information on the probability of experiencing a certain level of monetary loss when a given damage state is attained. Fragility curves and loss function developed in this study can be directly used within the FEMA P-58 framework for the seismic performance assessment of RC frame buildings with masonry infills.

Fragility curves and loss functions for RC structural components with smooth rebars

  • Cardone, Donatello
    • Earthquakes and Structures
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    • v.10 no.5
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    • pp.1181-1212
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    • 2016
  • Fragility and loss functions are developed to predict damage and economic losses due to earthquake loading in Reinforced Concrete (RC) structural components with smooth rebars. The attention is focused on external/internal beam-column joints and ductile/brittle weak columns, designed for gravity loads only, using low-strength concrete and plain steel reinforcing bars. First, a number of damage states are proposed and linked deterministically with commonly employed methods of repair and related activities. Results from previous experimental studies are used to develop empirical relationships between damage states and engineering demand parameters, such as interstory and column drift ratios. Probability distributions are fit to the empirical data and the associated statistical parameters are evaluated using statistical methods. Repair costs for damaged RC components are then estimated based on detailed quantity survey of a number of pre-70 RC buildings, using Italian costing manuals. Finally, loss functions are derived to predict the level of monetary losses to individual RC components as a function of the experienced response demand.

Effects of ground motion scaling on nonlinear higher mode building response

  • Wood, R.L.;Hutchinson, T.C.
    • Earthquakes and Structures
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    • v.3 no.6
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    • pp.869-887
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    • 2012
  • Ground motion scaling techniques are actively debated in the earthquake engineering community. Considerations such as what amplitude, over what period range and to what target spectrum are amongst the questions of practical importance. In this paper, the effect of various ground motion scaling approaches are explored using three reinforced concrete prototypical building models of 8, 12 and 20 stories designed to respond nonlinearly under a design level earthquake event in the seismically active Southern California region. Twenty-one recorded earthquake motions are selected using a probabilistic seismic hazard analysis and subsequently scaled using four different strategies. These motions are subsequently compared to spectrally compatible motions. The nonlinear response of a planar frameidealized building is evaluated in terms of plasticity distribution, floor level acceleration and uncorrelated acceleration amplification ratio distributions; and interstory drift distributions. The most pronounced response variability observed in association with the scaling method is the extent of higher mode participation in the nonlinear demands.

Seismic Performance Evaluation of Special Reinforced Concrete Moment Resisting Frames With Hybrid Slit-Friction Damper (복합 슬릿-마찰 감쇠장치가 적용된 철근 콘크리트 특수 모멘트 저항골조의 내진성능 평가)

  • Lee, Joon-Ho;Kim, Gee-Cheol;Kim, Jin-Koo
    • Journal of Korean Association for Spatial Structures
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    • v.17 no.4
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    • pp.35-42
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    • 2017
  • This study develops a new hybrid passive energy dissipation device for seismic rehabilitation of an existing structure. The device is composed of a friction damper combined with a steel plate with vertical slits as a hysteretic damper. Analytical model is developed for the device, and the capacity of the hybrid device to satisfy a given target performance is determined based on the ASCE/SEI 7-10 process. The effect of the device is verified by nonlinear dynamic analyses using seven earthquake records. The analysis results show that the dissipated inelastic energy is concentrated on the hybrid damper and the maximum interstory drift of the SMRF with damping system satisfies the requirement of the current code.

Modal pushover analysis of self-centering concentrically braced frames

  • Tian, Li;Qiu, Canxing
    • Structural Engineering and Mechanics
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    • v.65 no.3
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    • pp.251-261
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    • 2018
  • Self-centering concentrically braced frames (SCCBFs) are emerging as high performance seismically resistant braced framing system, due to the capacity of withstanding strong earthquake attacks and promptly recovering after events. To get a further insight into the seismic performance of SCCBFs, systematical evaluations are currently conducted from the perspective of modal contributions. In this paper, the modal pushover analysis (MPA) approach is utilized to obtain the realistic seismic demands by summarizing the contribution of each single vibration mode. The MPA-based results are compared with the exact results from nonlinear response history analysis. The adopted SCCBFs originate from existing buckling-restrained braced frames (BRBF), which are also analyzed for purpose of comparison. In the analysis of these comparable framing systems, interested performance indices that closely relate to the structural damage degree include the interstory drift ratio, floor acceleration, and absorbed hysteretic energy. The study shows that the MPA approach produces acceptable predictions in comparison to the exact results for SCCBFs. In addition, the high-modes effect on the seismic behavior increases with the building height, and is more evident in the SCCBFs than the BRBFs.

Optimization of fuzzy controller for nonlinear buildings with improved charged system search

  • Azizi, Mahdi;Ghasemi, Seyyed Arash Mousavi;Ejlali, Reza Goli;Talatahari, Siamak
    • Structural Engineering and Mechanics
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    • v.76 no.6
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    • pp.781-797
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    • 2020
  • In recent years, there is an increasing interest to optimize the fuzzy logic controller with different methods. This paper focuses on the optimization of a fuzzy logic controller applied to a seismically excited nonlinear building. In most cases, this problem is formulated based on the linear behavior of the structure, however in this paper, four sets of objective functions are considered with respect to the nonlinear responses of the structure as the peak interstory drift ratio, the peak level acceleration, the ductility factor and the maximum control force. The Improved Charged System Search is used to optimize the membership functions and the rule base of the fuzzy controller. The obtained results of the optimized and the non-optimized fuzzy controllers are compared to the uncontrolled responses of the structure. Also, the performance of the utilized method is compared with various classical and advanced optimization algorithms.