• Title/Summary/Keyword: nonlinear time history

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Non-linear Time History Analysis of Piloti-Type High-rise RC Buildings (필로티형 고층 RC건물의 비선형시간이력해석)

  • Ko, Dong-Woo;Lee, Han-Seon
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.1
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    • pp.35-43
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    • 2009
  • Two types of piloti-type high-rise RC building structures having irregularity in the lower two stories were selected as prototypes, and nonlinear time history analysis was performed using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. One of the buildings studied had a symmetrical moment-resisting frame (BF), while the other had an infilled shear wall in only one of the exterior frames (ESW). A fiber model, consisting of concrete and reinforcing bar represented from the stress-strain relationship, was adapted and used to simulate the nonlinearity of members, and MVLEM (Multi Vertical Linear Element Model) was used to simulate the behavior of the wall. The analytical results simulate the behavior of piloti-type high-rise RC building structures well, including the stiffness and yield force of piloti stories, the rocking behavior of the upper structure and the variation of the axial stiffness of the column due to variation in loading condition. However, MVLEM has a limitation in simulating the abrupt increasing lateral stiffness of a wall, due to the torsional mode behavior of the building. The design force obtained from a nonlinear time history analysis was shown to be about $20{\sim}30%$ smaller than that obtained in the experiment. For this reason, further research is required to match the analytical results with real structures, in order to use nonlinear time history analysis in designing a piloti-type high-rise RC building.

Horizontal only and horizontal-vertical combined earthquake effects on three R/C frame building structures through linear time-history analysis (LTHA): An implementation to Turkey

  • Selcuk Bas;Mustafa A. Bilgin
    • Computers and Concrete
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    • v.34 no.3
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    • pp.329-346
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    • 2024
  • In this study, it is aimed to investigate the vertical seismic performance of reinforced concrete (R/C) frame buildings in two different building stocks, one of which consists of those designed as per the previous Turkish Seismic Code (TSC-2007) that does not consider the vertical earthquake load, and the other of which consists of those designed as per the new Turkish Seismic Code (TSCB-2018) that considers the vertical earthquake load. For this aim, three R/C buildings with heights of 15 m, 24 m and 33 m are designed separately as per TSC-2007 and TSCB-2018 based on some limitations in terms of seismic zone, soil class and structural behavior factor (Rx/Ry) etc. The vertical earthquake motion effects are identified according to the linear time-history analyses (LTHA) that are performed separately for only horizontal (H) and combined horizontal+vertical (H+V) earthquake motions. LTHA is performed to predict how vertical earthquake motion affects the response of the designed buildings by comparing the linear response parameters of the base shear force, the base overturning, the base axial force, top-story vertical displacement. Nonlinear time-history analysis (NLTHA) is generally required for energy dissipative buildings, not required for design of buildings. In this study, the earthquake records are scaled to force the buildings in the linear range. Since nonlinear behavior is not expected from the buildings herein, the nonlinear time-history analysis (NLTHA) is not considered. Eleven earthquake acceleration records are considered by scaling them to the design spectrum given in TSCB-2018. The base shear force is obtained not to be affected from the combined H+V earthquake load for the buildings. The base overturning moment outcomes underline that the rigidity of the frame system in terms of the dimensions of the columns can be a critical parameter for the influence of the vertical earthquake motion on the buildings. In addition, the building stock from TSC-2007 is estimated to show better vertical earthquake performance than that of TSCB-2018. The vertical earthquake motion is found out to be highly effective on the base axial force of 33 m building rather than 15 m and 24 m buildings. Thus, the building height is a particularly important parameter for the base axial force. The percentage changes in the top-story vertical displacement of the buildings designed for both codes show an increase parallel to that in the base axial force results. To extrapolate more general results, it is clear to state that many buildings should be analyzed.

Computing input energy response of MDOF systems to actual ground motions based on modal contributions

  • Ucar, Taner
    • Earthquakes and Structures
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    • v.18 no.2
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    • pp.263-273
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    • 2020
  • The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.

The Response Characteristics of Push-over and Nonlinear Time History Analysis with Variations in the Upper Stories of the Mixed Building Structure (복합구조물의 상부층수 변화에 따른 탄소성 정적 및 동적 응답특성)

  • 강병두;전대한;김재웅
    • Journal of the Earthquake Engineering Society of Korea
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    • v.5 no.5
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    • pp.73-83
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    • 2001
  • The mass and stiffness of upper wall-lower frame system(mixed building structures) change sharply at transfer floor due to different structural system in upper and lower part. These mixed building structures generally show the stiffness, weight or geometric vertical irregularities. The purpose of this study is to investigate the response characteristics of these structures by push-over analysis and nonlinear time history analysis. For four types of analysed models, only the variation of upper wall stories was considered. The conclusions of this study are following; (1) In the push-over analysis, yielding hinges in beams and columns of lower frame occurred at the base shear of similar magnitude in all models. But as the number of stories of upper wall increases, yielding hinges at ends of coupling beams were observed in the small magnitude of base shear. (2) In the nonlinear time history analysis, yielding of lower frame occurred at beams with as small ground acceleration as 55gal, and in upper walls yielding was concentrated on coupling beams and shear walls near the transfer floor. (3) As the number of stories of upper walls decreases, the story stiffness of the lower frames decreased relatively and the occurrence of soft stories in the lower frame was observed.

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Prediction of Nonlinear Seismic Response (지진하중에 의한 구조물의 비선형 거동 예측)

  • Kim, Hee Joong
    • Journal of Korean Society of Steel Construction
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    • v.8 no.4 s.29
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    • pp.77-84
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    • 1996
  • The structural members under seismic loading actually show inelastic behavior, so the inelastic responses should be calculated for the seismic design of structures or estimating the structural damage level. Although direct time history analysis may calculate the exact dynamic nonlinear responses for given ground motions, this approach involves a high computational cost and long period. Therefore, it should be developed the approach to estimate nonlinear responses for the practical purpose. The artificial earthquake accelerograms were generated to obtain the smoothed responses spectra, and the samples of generated accelerogram for each seismic event was used to examine average nonlinear response spectra. The stabilized response spectra for each earthquake event was used to evaluate the effects of various yield strength ratios, damping values and nonlinear hysteretic models. The approach, which can simply predict the nonlinear seismic responses of structures, was shown in this study.

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Structural identification based on incomplete measurements with iterative Kalman filter

  • Ding, Yong;Guo, Lina
    • Structural Engineering and Mechanics
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    • v.59 no.6
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    • pp.1037-1054
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    • 2016
  • Structural parameter evaluation and external force estimation are two important parts of structural health monitoring. But the structural parameter identification with limited input information is still a challenging problem. A new simultaneous identification method in time domain is proposed in this study to identify the structural parameters and evaluate the external force. Each sampling point in the time history of external force is taken as the unknowns in force evaluation. To reduce the number of unknowns for force evaluation the time domain measurements are divided into several windows. In each time window the structural excitation is decomposed by orthogonal polynomials. The time-variant excitation can be represented approximately by the linear combination of these orthogonal bases. Structural parameters and the coefficients of decomposition are added to the state variable to be identified. The extended Kalman filter (EKF) is augmented and selected as the mathematical tool for the implementation of state variable evaluation. The proposed method is validated numerically with simulation studies of a time-invariant linear structure, a hysteretic nonlinear structure and a time-variant linear shear frame, respectively. Results from the simulation studies indicate that the proposed method is capable of identifying the dynamic load and structural parameters fairly accurately. This method could also identify the time-variant and nonlinear structural parameter even with contaminated incomplete measurement.

Nonlinear Response Analysis of Multi-Degree-of-Freedom Building Structures Using Response Spectrum Method (응답스펙트럼법에 의한 고층 건축물의 탄소성 지진응답해석법)

  • Jun, Dae-Han
    • Journal of the Earthquake Engineering Society of Korea
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    • v.1 no.4
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    • pp.1-9
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    • 1997
  • This paper examined various aspects of a linear and a nonlinear response spectrum method in seismic response analysis of multi-story building structures. The response spectrum method that has been widely used in the analysis of linear structures was proposed different mode superposition method by several ivestigators, and the differences between combinations with an elastic modal analysis reviwed closely. It seems, however, that this method is not used to nonlinear seismic analysis. It is the purpose of this paper to propose an alternative method by means of which a nonlinear MDOF structure with long period may be analysed by an extention of response spectrum method. For nonlinear seismic analysis of high-rise building structures using technique proposed in this study, it is intended to serve primarily as a tool in preliminary designs instead of time history analysis.

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Performance-based framework for soil-structure systems using simplified rocking foundation models

  • Smith-Pardo, J. Paul
    • Structural Engineering and Mechanics
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    • v.40 no.6
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    • pp.763-782
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    • 2011
  • Results from nonlinear time-history analyses of wall-frame structural models indicate that the condition of vulnerable foundations -for which uplifting and reaching the bearing capacity of the supporting soil can occur before yielding at the base of the shear walls- may not be necessarily detrimental to the drift response of buildings under strong ground motions. Analyses also show that a soil-foundation system can inherently have deformation capacity well in excess of the demand and thus act as a source of energy dissipation that protects the structural integrity of the shear walls.

Seismic response of RC structures rehabilitated with SMA under near-field earthquakes

  • Shiravand, M.R.;Khorrami Nejad, A.;Bayanifar, M.H.
    • Structural Engineering and Mechanics
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    • v.63 no.4
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    • pp.497-507
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    • 2017
  • During recent earthquakes, a significant number of concrete structures suffered extensive damage. Conventional reinforced concrete structures are designed for life-time safety that may see permanent inelastic deformation after severe earthquakes. Hence, there is a need to utilize adequate materials that have the ability to tolerate large deformation and get back to their original shape. Super-elastic shape memory alloy (SMA) is a smart material with unique properties, such as the ability to regain undeformed shape by unloading or heating. In this research, four different stories (three, five, seven and nine) of reinforced concrete (RC) buildings have been studied and subjected to near-field ground motions. For each building, two different types of reinforcement detailing are considered, including (1) conventional steel reinforcement (RC frame) and (2) steel-SMA reinforcement (SMA RC frame), with SMA bars being used at plastic zones of beams and steel bars in other regions. Nonlinear time history analyses have been performed by "SeismoStruct" finite element software. The results indicate that the application of SMA materials in plastic hinge regions of the beams lead to reduction of the residual displacement and consequently post-earthquake repairs. In general, it can be said that shape memory alloy materials reduce structural damage and retrofit costs.

Seismic Evaluation of Shear Wall System by Nonlinear Static Analysis Procedures (비선형 정적 해석을 통한 벽식구조물의 내진성능 평가)

  • 안성기;송정원;송진규;이수곤
    • Proceedings of the Korea Concrete Institute Conference
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    • 2000.10a
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    • pp.63-68
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    • 2000
  • Concrete is popular as a building material, however it is inherently brittle and performs poorly during earthquakes if nor reinforced properly. Traditional retrofit design techniques assume that buildings respond elastically to earthquakes. This assumption simplifies the analysis procedure but can lead to an erroneous conclusion. The complete nonlinear time history analysis is considered overly complex and impractical for general use. Simplified nonlinear analysis methods, referred to as nonlinear static analysis procedures, include the capacity spectrum method(CSM) developed in detail at ATC-40 and the displacement coefficient method(DCM) utilized at FEMA-273. In this study wall APT system. The results were compared and analyzed. The program used was neaMAX-3D to express nonlinear material.

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