• Title, Summary, Keyword: SDOF Building

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Development of Artificial Neural Network Model for Prediction of Seismic Response of Building with Soil-structure Interaction (지반-상부 구조물 효과를 고려한 인공신경망 기반 지진 응답 예측 모델 개발)

  • Won, Jongmuk;Shin, Jiuk
    • Journal of the Korean Geotechnical Society
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    • v.36 no.8
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    • pp.7-15
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    • 2020
  • Constructing the maximum displacement and shear force database for the seismic performance of building with soil-structure interaction under varied earthquake scenarios and geotechnical conditions is critical in developing the neural network-based prediction models. However, using the available 3D FEM-based computer simulation techniques causes high computation costs in developing the database. This study introduces the framework of developing the artificial neural network (ANN) model to predict the seismic performance of building at given Poisson's ratio and shear wave velocity of soil. The simple Single-Degree-Of-Freedom system was used to develop the database and the performance of the developed neural network model is discussed through the evaluated coefficient of determination (R2). In addition, ANN models were developed for 90~100% percentile of the database to assess the accuracy of the developed ANN models in each percentile.

Seismic response and damage development analyses of an RC structural wall building using macro-element

  • Hemsas, Miloud;Elachachi, Sidi-Mohammed;Breysse, Denys
    • Structural Engineering and Mechanics
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    • v.51 no.3
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    • pp.447-470
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    • 2014
  • Numerical simulation of the non-linear behavior of (RC) structural walls subjected to severe earthquake ground motions requires a reliable modeling approach that includes important material characteristics and behavioral response features. The objective of this paper is to optimize a simplified method for the assessment of the seismic response and damage development analyses of an RC structural wall building using macro-element model. The first stage of this study investigates effectiveness and ability of the macro-element model in predicting the flexural nonlinear response of the specimen based on previous experimental test results conducted in UCLA. The sensitivity of the predicted wall responses to changes in model parameters is also assessed. The macro-element model is next used to examine the dynamic behavior of the structural wall building-all the way from elastic behavior to global instability, by applying an approximate Incremental Dynamic Analysis (IDA), based on Uncoupled Modal Response History Analysis (UMRHA), setting up nonlinear single degree of freedom systems. Finally, the identification of the global stiffness decrease as a function of a damage variable is carried out by means of this simplified methodology. Responses are compared at various locations on the structural wall by conducting static and dynamic pushover analyses for accurate estimation of seismic performance of the structure using macro-element model. Results obtained with the numerical model for rectangular wall cross sections compare favorably with experimental responses for flexural capacity, stiffness, and deformability. Overall, the model is qualified for safety assessment and design of earthquake resistant structures with structural walls.

Practical seismic assessment of unreinforced masonry historical buildings

  • Pardalopoulos, Stylianos I.;Pantazopoulou, Stavroula J.;Ignatakis, Christos E.
    • Earthquakes and Structures
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    • v.11 no.2
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    • pp.195-215
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    • 2016
  • Rehabilitation of historical unreinforced masonry (URM) buildings is a priority in many parts of the world, since those buildings are a living part of history and a testament of human achievement of the era of their construction. Many of these buildings are still operational; comprising brittle materials with no reinforcements, with spatially distributed mass and stiffness, they are not encompassed by current seismic assessment procedures that have been developed for other structural types. To facilitate the difficult task of selecting a proper rehabilitation strategy - often restricted by international treaties for non-invasiveness and reversibility of the intervention - and given the practical requirements for the buildings' intended reuse, this paper presents a practical procedure for assessment of seismic demands of URM buildings - mainly historical constructions that lack a well-defined diaphragm action. A key ingredient of the method is approximation of the spatial shape of lateral translation, ${\Phi}$, that the building assumes when subjected to a uniform field of lateral acceleration. Using ${\Phi}$ as a 3-D shape function, the dynamic response of the system is evaluated, using the concepts of SDOF approximation of continuous systems. This enables determination of the envelope of the developed deformations and the tendency for deformation and damage localization throughout the examined building for a given design earthquake scenario. Deformation demands are specified in terms of relative drift ratios referring to the in-plane and the out-of-plane seismic response of the building's structural elements. Drift ratio demands are compared with drift capacities associated with predefined performance limits. The accuracy of the introduced procedure is evaluated through (a) comparison of the response profiles with those obtained from detailed time-history dynamic analysis using a suite of ten strong ground motion records, five of which with near-field characteristics, and (b) evaluation of the performance assessment results with observations reported in reconnaissance reports of the field performance of two neoclassical torsionally-sensitive historical buildings, located in Thessaloniki, Greece, which survived a major earthquake in the past.

Dimensional analysis of base-isolated buildings to near-fault pulses

  • Istrati, Denis;Spyrakos, Constantine C.;Asteris, Panagiotis G.;Panou-Papatheodorou, Eleni
    • Structural Engineering and Mechanics
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    • v.75 no.1
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    • pp.33-47
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    • 2020
  • In this paper the dynamic behavior of an isolated building subjected to idealized near-fault pulses is investigated. The building is represented with a simple 2-DOF model. Both linear and non-linear behavior of the isolation system is considered. Using dimensional analysis, in conjunction with closed form mathematical idealized pulses, appropriate dimensionless parameters are defined and self-similar curves are plotted on dimensionless graphs, based on which various conclusions are reached. In the linear case, the role of viscous damping is examined in detail and the existence of an optimum value of damping along with its significant variation with the number of half-cycles is shown. In the nonlinear case, where the behavior of the building depends on the amplitude of the excitation, the benefits of dimensional analysis are evident since the influence of the dimensionless 𝚷-terms is easily examined. Special consideration is given to the normalized strength of the non-linear isolation system that appears to play a complex role which greatly affects the response of the 2-DOF. In the last part of the paper, a comparison of the responses to idealized pulses between a linear fixed-base SDOF and the respective isolated 2-DOF with both linear and non-linear damping is conducted and it is shown that, under certain values of the superstructure and isolation system characteristics, the use of an isolation system can amplify both the normalized acceleration and displacement of the superstructure.

Equivalent damping ratio based on the earthquake response of a SDOF structure with a MR damper (MR 감쇠기가 설치된 단자유도 구조물의 지진응답에 기초한 등가감쇠비)

  • Park, Ji-Hun;Moon, Byoung-Wook;Min, Kyung-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.879-885
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    • 2006
  • Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally, response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

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Equivalent Damping Ratio Based on Earthquake Characteristics of a SDOF Structure with an MR Damper (지진특성에 따른 MR감쇠기가 설치된 단자유도 구조물의 등가감쇠비)

  • Moon, Byoung-Wook;Park, Ji-Hun;Lee, Sung-Kyung;Min, Kyung-Won
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.1
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    • pp.87-93
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    • 2008
  • Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

Evaluation of Site-dependent Ductility Factors for Elastic Perfectly Plastic SDOF Systems (토질조건에 따른 탄소성 단자유도 구조물의 연성계수 평가)

  • Kang, Cheol-Kyu;Choi, Byong-Jeong
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.4
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    • pp.11-20
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    • 2004
  • This paper suggests the site-dependent ductility factor which is a key component of response modification factor(R). To compute the ductility factor, a group of 1,860 ground motions recorded from 47 earthquake was considered. Based on the local site conditions at the recording station, ground motions were classified into four groups according to average shear wave velocity. This site classification was consistent with site categories of the UBC(1997), NEHRP(1997) and IBC 2000(1997). Based on the results of regression analysis, a simplified equations were proposed to compute site-dependent ductility factors. The proposed equations were relatively simple and provide a good estimation of mean ductility factors. Based on the proposed equation, ductility factors considering the site conditions can be evaluated in accordance with the present building codes.

Equivalent damping ratio based on earthquake characteristics of a SDOF structure with an MR damper (지진특성에 따른 MR 감쇠기가 설치된 단자유도 구조물의 등가감쇠비)

  • Moon, Byoung-Wook;Park, Ji-Hun;Lee, Sung-Kyung;Min, Kyung-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.459-464
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    • 2007
  • Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally, response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

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Numerical verification of a dual system's seismic response

  • Phocas, Marios C.;Sophocleous, Tonia
    • Earthquakes and Structures
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    • v.3 no.5
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    • pp.749-766
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    • 2012
  • Structural control through integration of passive damping devices within the building structure has been increasingly implemented internationally in the last years and has proven to be a most promising strategy for earthquake safety. In the present paper an alternative configuration of an innovative energy dissipation mechanism that consists of slender tension only bracing members with closed loop and a hysteretic damper is investigated in its dynamic behavior. The implementation of the adaptable dual control system, ADCS, in frame structures enables a dual function of the component members, leading to two practically uncoupled systems, i.e., the primary frame, responsible for the normal vertical and horizontal forces and the closed bracing-damper mechanism, for the earthquake forces and the necessary energy dissipation. Three representative international earthquake motions of differing frequency contents, duration and peak ground acceleration have been considered for the numerical verification of the effectiveness and properties of the SDOF systems with the proposed ADCS-configuration. The control mechanism may result in significant energy dissipation, when the geometrical and mechanical properties, i.e., stiffness and yield force of the integrated damper, are predefined. An optimum damper ratio, DR, defined as the ratio of the stiffness to the yield force of the hysteretic damper, is proposed to be used along with the stiffness factor of the damper's- to the primary frame's stiffness, in order for the control mechanism to achieve high energy dissipation and at the same time to prevent any increase of the system's maximum base shear and relative displacements. The results are summarized in a preliminary design methodology for ADCS.

Softening and hardening tuned mass dampers

  • Khalili, Mohammad Khalil;Badamchi, Karim
    • Earthquakes and Structures
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    • v.14 no.5
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    • pp.459-465
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    • 2018
  • Reducing response of buildings during earthquakes by mass dampers, has been examined in many articles and books. Nowadays, many researchers are trying to realistically examine this type of dampers by new methods of performance. In this paper, for the better study of tuned mass damper (TMD), two schematic models are presented for a passive TMD with softening stiffness (softening TMD) and a passive TMD with hardening stiffness (hardening TMD). Then by modeling and analysis of the damper on a single degree of freedom (SDOF) structure and an 11-story steel building, the dampers performance was evaluated. State space was used for damper and structure modeling and to solve nonlinear equations, the Newton-Raphson method was used. The results show that when the structure is subjected to the Chi-Chi earthquake, response of the sixth floor in the system without TMD reduces 54.0% in comparison to the structure with softening TMD. This percentage of reduction for hardening TMD is 55.0%. Also for the Tabas earthquake, reduction in the RMS acceleration of the sixth floor in the system with hardening TMD is 96.2% more than the structure without TMD. This percentage of reduction for hardening TMD is 96.3%.