• Title, Summary, Keyword: SDOF Building

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Response transformation factors for deterministic-based and reliability-based seismic design

  • Bojorquez, Eden;Bojorquez, Juan;Ruiz, Sonia E.;Reyes-Salazar, Alfredo;Velazquez-Dimas, Juan
    • Structural Engineering and Mechanics
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    • v.46 no.6
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    • pp.755-773
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    • 2013
  • One of the main requirements of the seismic design codes must be its easy application by structural engineers. The use of practically-applicable models or simplified models as single-degree-of-freedom (SDOF) systems is a good alternative to achieve this condition. In this study, deterministic and probabilistic response transformation factors are obtained to evaluate the response in terms of maximum ductility and maximum interstory drifts of multi-degree-of-freedom (MDOF) systems based on the response of equivalent SDOF systems. For this aim, five steel frames designed with the Mexican City Building Code (MCBC) as well as their corresponding equivalent SDOF systems (which represent the characteristics of the frames) are analyzed. Both structural systems are subjected to ground motions records. For the MDOF and the simplified systems, incremental dynamic analyses IDAs are developed in first place, then, structural demand hazard curves are obtained. The ratio between the IDAs curves corresponding to the MDOF systems and the curves corresponding to the simplified models are used to obtain deterministic response transformation factors. On the other hand, demand hazard curves are used to calculate probabilistic response transformation factors. It was found that both approaches give place to similar results.

Evaluation of Seismic Performance of Mixed Building Structures by using the Nonlinear Displacement Mode Method (비선형 변위모드법을 적용한 복합구조물의 내진성능평가)

  • 김부식;송호산
    • Journal of the Earthquake Engineering Society of Korea
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    • v.7 no.6
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    • pp.71-80
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    • 2003
  • Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

Closed Form Formulas for Equivalent Damping Ratios of a Linear Structure Equipped with Damping Devices (제진장치가 설치된 구조물의 등가감쇠비)

  • Hwang, Jae-Seung;Lee, Sang-Hyun;Min, Kyung-Won
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.370-377
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    • 2002
  • Hwang et al (2001) proposed a new method for an evaluation of equivalent damping ratios of a linear structure with linear or nonlinear damping devices. This procedure has a disadvantage that it requires time history analysis for the whole system including damping devices, which may be troublesome for practical application. To tackle this problem closed form formulas for equivalent damping ratios are proposed in this study. It is assumed that the responses of MDOF system can be reproduced by an equivalent SDOF system which vibrates in a fundamental mode. The numerical analyses of a ten-story building equipped with linear viscous damper or active mass damper or friction damper show the effectiveness of equivalent SDOF model and closed form formulas.

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Evaluation of the Equivalent First Modal Damping Ratio of a Structure with Additional Damping Devices (부가감쇠 장치가 설치된 구조물의 1차 모드 등가 감쇠비 산정)

  • Lee, Sang-Hyun;Min, Kyung-Won;Hwang, Jae-Seung;Lee, Young-Cheol
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.459-466
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    • 2002
  • The purpose of this study is to propose a new method for evaluating equivalent damping ratios of a structure with supplemental damping devices to assess their control effect quantitatively. A MDOF system is transformed to an equivalent SDOF system based on the assumption that the first mode dominates structural response. Approximate closed-form formulas for the evaluation of the first damping ratio are presented for various damping devices. Through numerical analysis of a ten-story building equipped with damping devices, the effectiveness of equivalent SDOF model and closed form formulas are verified.

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Evaluation of Inelastic Earthquake Response of MDOF System by Equivalent SDOF System (등가 1자유도계에 의한 다자유도 비선형 지진응답 산정)

  • Kim, Bu-Sik;Noh, Phil-Sung;Jun, Dae-Han;Song, Ho-San
    • Journal of Korean Association for Spatial Structures
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    • v.2 no.2
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    • pp.45-49
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    • 2002
  • Current seismic design codes for building structures are based on the methods which can provide enough capacity to satisfy objected performance level and exactly evaluate the seismic performance of buildings. This paper is to suggest the method of inference of inelastic earthquake response obtained from MDOF system by equivalent SDOF system, and to prove the validity. The analysis results form simple model shows a good application possibility.

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Dynamic Characteristic Identification on Steel Column bases Installed in Pendulum-type Earthquake Response Observatory

  • Choi, Jae-Hyouk;Ohi, Kenichi
    • Journal of Mechanical Science and Technology
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    • v.18 no.12
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    • pp.2225-2235
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    • 2004
  • An observatory termed 'Steel Swing' has been developed, where a 15000 kg pendulum is hanged from a stiff steel frame. A building element can be tested after inserted between the pendulum and the frame. Free vibration, forced vibration tests and earthquake monitoring were performed on an exposed-type steel column base. The response records monitored during natural earthquakes were used to identify the vibration property of the specimen. Identified system gain was approximated by a theoretical gain of linear SDOF system, and the response calculated based on such a linear system agrees with the monitored response fairly well. This research technique can be applied to check the behaviors of new materials and new details of connections and the safety of non-structural elements as well.

Evaluation of Seismic Design Force by Earthquake Response Analysis of Water Tanks Installed in RC Buildings (건축물에 설치된 물탱크의 지진응답해석을 통한 설계하중 평가)

  • Baek, Eun Rim;Oh, Ji Hyeon;Choi, Hyoung Suk;Lee, Sang Ho
    • Journal of the Earthquake Engineering Society of Korea
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    • v.23 no.4
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    • pp.221-229
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    • 2019
  • Several water tanks installed in the building were damaged during the Gyeongju earthquake (2016) and the Pohang earthquake (2017). Since a water tank for fire protection is very important component, seismic safety should be ensured. In this study, an interaction between a water tank and a building was studied by the dynamic analysis of the RC building with the water tank. In case the water tank was installed on the roof of the RC building, it was confirmed that it did not significantly affect the response of the building. Based on the result, dynamic response characteristics of the water tank in the building were studied using two SDOF models represented dynamic behavior of the water tanks under earthquake. An earthquake time-history analysis was carried out with variables of aspect ratio of the tank, story of the building, and installed location in the building using three kinds of earthquakes.

Experimental evaluation of aerodynamic damping of square super high-rise buildings

  • Quan, Yong;Gu, Ming;Tamura, Yukio
    • Wind and Structures
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    • v.8 no.5
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    • pp.309-324
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    • 2005
  • Aerodynamic damping often plays an important role in estimations of wind induced dynamic responses of super high-rise buildings. Across- and along-wind aerodynamic damping ratios of a square super high-rise building with a height of 300 m are identified with the Random Decrement technique (RDT) from random vibration responses of the SDOF aeroelastic model in simulated wind fields. Parametric studies on effects of reduced wind velocity, terrain type and structural damping ratio on the aerodynamic damping ratios are further performed. Finally formulas of across- and along-wind aerodynamic damping ratios of the square super high-rise building are derived with curve fitting technique and accuracy of the formulas is verified.

Damage-based optimization of large-scale steel structures

  • Kaveh, A.;Kalateh-Ahani, M.;Fahimi-Farzam, M.
    • Earthquakes and Structures
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    • v.7 no.6
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    • pp.1119-1139
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    • 2014
  • A damage-based seismic design procedure for steel frame structures is formulated as an optimization problem, in which minimization of the initial construction cost is treated as the objective of the problem. The performance constraint of the design procedure is to achieve "repairable" damage state for earthquake demands that are less severe than the design ground motions. The Park-Ang damage index is selected as the seismic damage measure for the quantification of structural damage. The charged system search (CSS) algorithm is employed as the optimization algorithm to search the optimum solutions. To improve the time efficiency of the solution algorithm, two simplifying strategies are adopted: first, SDOF idealization of multi-story building structures capable of estimating the actual seismic response in a very short time; second, fitness approximation decreasing the number of fitness function evaluations. The results from a numerical application of the proposed framework for designing a twelve-story 3D steel frame structure demonstrate its efficiency in solving the present optimization problem.

Design of Friction Dampers for Seismic Response Control of a SDOF Building (단자유도 건물의 지진응답제어를 위한 마찰감쇠기 설계)

  • Min, Kyung-Won;Seong, Ji-Young
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.1
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    • pp.22-28
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    • 2010
  • Approximate analysis for a building installed with a friction damper is performed to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor(DMF). It is found out that DMF is dependent on friction force ratio and resonance frequency. Approximation of DMF and equivalent damping ratio of a friction damper is proposed with such assumption that the building with a friction damper shows harmonic steady-state response and narrow banded response behavior near resonance frequency. Linear transfer function from input external force to output building displacement is suggested from the simplified DMF equation. Root mean square of a building displacement is derived under earthquake-like random excitation. Finally, design procedure of a friction damper is proposed by finding friction force corresponding to target control ratio. Numerical analysis is carried out to verify the proposed design procedure.