• Title, Summary, Keyword: acceleration response

Search Result 1,127, Processing Time 0.04 seconds

Dynamic Response of Cantilevered Beams Subjected to a Travelling Mass with a Constant Acceleration (일정 가속 주행질량에 의한 외팔보의 동적응답)

  • 류봉조;윤충섭;김희중;이규섭
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.320-325
    • /
    • 2004
  • The paper deals with the dynamic response of a cantilevered beam under a travelling mass with constant acceleration. Governing equations of motion taking into account all inertia effects of the travelling mass are derived by Galerkin's mode summation method, and Runge-Kutta integration method is applied to solve the differential equations. The effects of the speed, acceleration and the magnitude of the travelling mass on the response of the beam are fully investigated. A variety of numerical results allows us to draw important conclusions for structural design purposes.

  • PDF

Damage detection of railway bridges using operational vibration data: theory and experimental verifications

  • Azim, Md Riasat;Zhang, Haiyang;Gul, Mustafa
    • Structural Monitoring and Maintenance
    • /
    • v.7 no.2
    • /
    • pp.149-166
    • /
    • 2020
  • This paper presents the results of an experimental investigation on a vibration-based damage identification framework for a steel girder type and a truss bridge based on acceleration responses to operational loading. The method relies on sensor clustering-based time-series analysis of the operational acceleration response of the bridge to the passage of a moving vehicle. The results are presented in terms of Damage Features from each sensor, which are obtained by comparing the actual acceleration response from the sensors to the predicted response from the time-series model. The damage in the bridge is detected by observing the change in damage features of the bridge as structural changes occur in the bridge. The relative severity of the damage can also be quantitatively assessed by observing the magnitude of the changes in the damage features. The experimental results show the potential usefulness of the proposed method for future applications on condition assessment of real-life bridge infrastructures.

Site specific ground motion simulation and seismic response analysis for microzonation of Kolkata

  • Roy, Narayan;Sahu, R.B.
    • Geomechanics and Engineering
    • /
    • v.4 no.1
    • /
    • pp.1-18
    • /
    • 2012
  • The spatial variation of ground motion in Kolkata Metropolitan District (KMD) has been estimated by generating synthetic ground motion considering the point source model coupled with site response analysis. The most vulnerable source was identified from regional seismotectonic map for an area of about 350 km radius around Kolkata. The rock level acceleration time histories at 121 borehole locations in Kolkata for the vulnerable source, Eocene Hinge Zone, due to maximum credible earthquake (MCE) moment magnitude 6.2 were generated by synthetic ground motion model. Soil investigation data of 121 boreholes were collected from the report of Soil Data Bank Project, Jadavpur University, Kolkata. Surface level ground motion parameters were determined using SHAKE2000 software. The results are presented in the form of peak ground acceleration (PGA) at rock level and ground surface, amplification factor, and the response spectra at the ground surface for frequency 1.5 Hz, 3 Hz, 5 Hz and 10 Hz and 5% damping ratio. Site response study shows higher PGA in comparison with rock level acceleration. Maximum amplification in some portion in KMD area is found to be as high as 3.0 times compared to rock level.

Experimental validation of Kalman filter-based strain estimation in structures subjected to non-zero mean input

  • Palanisamy, Rajendra P.;Cho, Soojin;Kim, Hyunjun;Sim, Sung-Han
    • Smart Structures and Systems
    • /
    • v.15 no.2
    • /
    • pp.489-503
    • /
    • 2015
  • Response estimation at unmeasured locations using the limited number of measurements is an attractive topic in the field of structural health monitoring (SHM). Because of increasing complexity and size of civil engineering structures, measuring all structural responses from the entire body is intractable for the SHM purpose; the response estimation can be an effective and practical alternative. This paper investigates a response estimation technique based on the Kalman state estimator to combine multi-sensor data under non-zero mean input excitations. The Kalman state estimator, constructed based on the finite element (FE) model of a structure, can efficiently fuse different types of data of acceleration, strain, and tilt responses, minimizing the intrinsic measurement noise. This study focuses on the effects of (a) FE model error and (b) combinations of multi-sensor data on the estimation accuracy in the case of non-zero mean input excitations. The FE model error is purposefully introduced for more realistic performance evaluation of the response estimation using the Kalman state estimator. In addition, four types of measurement combinations are explored in the response estimation: strain only, acceleration only, acceleration and strain, and acceleration and tilt. The performance of the response estimation approach is verified by numerical and experimental tests on a simply-supported beam, showing that it can successfully estimate strain responses at unmeasured locations with the highest performance in the combination of acceleration and tilt.

Effect of Demand Spectrums on the Accuracy of Capacity Spectrum Method (요구곡선 산정방법에 따른 능력스펙트럼법의 유효성 평가 및 비교)

  • Kim, Hong-Jin;Min, Kyung-Won;Park, Min-Kyu
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.8 no.3
    • /
    • pp.33-42
    • /
    • 2004
  • While transforming the inelastic system into the equivalent elastic one gives an advantage of simpler analysis, the actual inelastic behavior of the system is hardly modeled in the capacity spectrum method (CSM). Therefore, the accuracy of CSM depends on the precise estimation of equivalent period and damping ratio as well as the modification of the elastic response spectrum and the corresponding demand spectrum. In this paper, the effect of demand spectrums on the accuracy of CSM is evaluated. First, the response reduction factors provided in ATC-40 and Euro Code are evaluated. Numerical analysis results indicated that the acceleration responses obtained using the factor of Euro Code are closer to the actual response than those obtained using the factors of ATC-40. Next, the accuracy of CSM is evaluated constructing the demand spectrum using the absolute acceleration responses and pseudo acceleration responses. The results obtained using the absolute acceleration responses were found to be generally larger than those obtained using the pseudo ones. Since CSM often underestimates the response, the use of absolute acceleration response gives the response relatively closer to the exact ones. However, the difference becomes negligible as the hardening ratio and the yield strength ratio become larger.

Analysis of Braking Response Time for Driving Take Based on Tri-axial Accelerometer

  • Shin, Hwa-Kyung;Lee, Ho-Cheol
    • The Journal of Korean Physical Therapy
    • /
    • v.22 no.6
    • /
    • pp.59-63
    • /
    • 2010
  • Purpose: Driving a car is an essential component of daily life. For safe driving, each driver must perceive sensory information and respond rapidly and accurately. Brake response time (BRT) is a particularly important factor in the total stopping distance of a vehicle, and therefore is an important factor in traffic accident prevention research. The purpose of the current study was (1) to compare accelerometer. BRTs analyzed by three different methods and (2) to investigate possible correlations between accelerometer-BRTs and foot switch-BRTs, which are measured method using a foot switch. Methods: Eighteen healthy subjects participated in this study. BRT was measured with either a tri-axial accelerometer or a footswitch. BRT with a tri-axial accelerometer was analyzed using three methods: maximum acceleration time, geometrical center, and center of maximum and minimum acceleration values. Results: Both foot switch-BRTs and accelerometer-BRTs were delayed. ANOVA for accelerometer BRTs yielded significant main effects for axis and analysis, while the interaction effect between axis and analysis was not significant. Calculating the Pearson correlation between accelerometer-BRT and foot switch-BRT, we found that maximum acceleration time and center of maximum and minimum acceleration values were significantly correlated with foot switch-BRT (p<0.05). The X axis of the geometrical center was significantly correlated with foot switch-BRTs (p<0.05), but Y and Z axes were not (p>0.05). Conclusion: These findings suggest that the maximum acceleration time and the center of maximum and minimum acceleration value are significantly correlated with foot switch-BRTs.

A Study on Evaluation of Floor Response Spectrum for Seismic Design of Non-Structural Components (비구조요소의 내진 설계를 위한 기존 층응답스펙트럼의 평가)

  • Choi, Kyung Suk;Yi, Waon Ho;Yang, Won-Jik;Kim, Hyung Joon
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.17 no.6
    • /
    • pp.279-291
    • /
    • 2013
  • The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

Output-only modal parameter identification for force-embedded acceleration data in the presence of harmonic and white noise excitations

  • Ku, C.J.;Tamura, Y.;Yoshida, A.;Miyake, K.;Chou, L.S.
    • Wind and Structures
    • /
    • v.16 no.2
    • /
    • pp.157-178
    • /
    • 2013
  • Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.

Integration of Measured Acceleration to Determine the Vibration Characteristics of Bridges (교량 진동특성 분석을 위한 실측 가속도의 적분)

  • ;;Lee, Sun-Goo;Lee, Mun-Taek
    • Computational Structural Engineering
    • /
    • v.9 no.4
    • /
    • pp.107-115
    • /
    • 1996
  • Displacement response is one of the important parameter to determine vibration characteristics of bridge structure. Reliable estimate of displacement response is obtained economically from integration of measured acceleration data in frequency domain. Proper sampling rate of frequency in discretization process of measured acceleration is proposed. Comparison of integrated and directly measured displacement response from laboratory experiment for a cantilever beam shows good agreement each other. Mode shape obtained from estimated displacement response also closely match with analytical result, thus the developed method is proved to be effective in practical use.

  • PDF

Characterization of earthquake ground motion of multiple sequences

  • Moustafa, Abbas;Takewaki, Izuru
    • Earthquakes and Structures
    • /
    • v.3 no.5
    • /
    • pp.629-647
    • /
    • 2012
  • Multiple acceleration sequences of earthquake ground motions have been observed in many regions of the world. Such ground motions can cause large damage to the structures due to accumulation of inelastic deformation from the repeated sequences. The dynamic analysis of inelastic structures under repeated acceleration sequences generated from simulated and recorded accelerograms without sequences has been recently studied. However, the characteristics of recorded earthquake ground motions of multiple sequences have not been studied yet. This paper investigates the gross characteristics of earthquake records of multiple sequences from an engineering perspective. The definition of the effective number of acceleration sequences of the ground shaking is introduced. The implication of the acceleration sequences on the structural response and damage of inelastic structures is also studied. A set of sixty accelerograms is used to demonstrate the general properties of repeated acceleration sequences and to investigate the associated structural inelastic response.