Identification of Modal Parameters of a Multistoried RC Building Using Ambient Vibration and Strong Vibration Records of Bhuj Earthquake, 2001

2013 ◽  
Vol 18 (3) ◽  
pp. 444-457 ◽  
Author(s):  
J. P. Singh ◽  
Pankaj Agarwal ◽  
Ashok Kumar ◽  
S. K. Thakkar
Keyword(s):  
Ambient Vibration ◽  
Modal Parameters ◽  
Bhuj Earthquake ◽  
Rc Building

Signal Processing for Operational Modal Analysis of a Jacket-Type Offshore Platform: Sea Test Study

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Xingxian Bao ◽  
Zhihui Liu ◽  
Chen Shi
Keyword(s):  
Noise Reduction ◽  
Modal Analysis ◽  
Measured Data ◽  
Offshore Platform ◽  
Operational Modal Analysis ◽  
Ambient Vibration ◽  
Data Matrix ◽  
Modal Parameters ◽  
Stability Diagrams ◽  
Free Decay

Operational modal analysis (OMA) has been widely used for large structures. However, measured signals are inevitably contaminated with noise and may not be clean enough for identifying the modal parameters with proper accuracy. The traditional methods to estimate modal parameters in noisy situation are usually absorbing the “noise modes” first, and then using the stability diagrams to distinguish the true modes from the “noise modes.” However, it is still difficult to sort out true modes because the “noise modes” will also tend to be stable as the model order increases. This study develops a noise reduction procedure for polyreference complex exponential (PRCE) modal analysis based on ambient vibration responses. In the procedure, natural excitation technique (NExT) is first applied to get free decay responses from measured (noisy) ambient vibration data, and then the noise reduction method based on solving the partially described inverse singular value problem (PDISVP) is implemented to reconstruct a filtered data matrix from the measured data matrix. In our case, the measured data matrix is block Hankel structured, which is constructed based on the free decay responses. The filtered data matrix should maintain the block Hankel structure and be lowered in rank. When the filtered data matrix is obtained, the PRCE method is applied to estimate the modal parameters. The proposed NExT-PDISVP-PRCE scheme is applied to field test of a jacket type offshore platform. Results indicate that the proposed method can improve the accuracy of OMA.

scholarly journals Identification of Modal Parameters of Bridges Using Ambient Vibration Measurements

2015 ◽  
Vol 2015 ◽  
pp. 1-21 ◽  
Author(s):  
Damir Zenunovic ◽  
Mirsad Topalovic ◽  
Radomir Folic
Keyword(s):  
Mathematical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Vibration Measurements ◽  
Ambient Vibration Tests ◽  
Real Nature ◽  
Vibration Tests ◽  
Ambient Vibration Measurements ◽  
Existing Bridges

The paper provides an overview of ambient vibration tests and numerical analysis performed in the framework of Project NATO SfP 983828. The aim of the research is the definition of the dynamic characteristics of bridges on the examples. The paper considers three case studies: two older existing bridges and one newly constructed bridge. A comparative analysis of natural frequencies and mode shapes, obtained by ambient vibration measurements (AVM) and mathematical models (AMs), was carried with the aim to demonstrate the usefulness of ambient vibration tests for identification of the modal parameters of the tested bridge structure. Agreement between AVM and AMs results is very good. The mode shapes are very similar. Some differences between computed and measured frequencies were obtained, which can be attributed to the real nature of the boundary conditions, the uncertainty in the material properties of structure elements, and the mathematical models assumptions.

scholarly journals Multi-scale model updating of a timber footbridge using experimental vibration data

2017 ◽  
Vol 34 (3) ◽  
pp. 754-780 ◽  
Author(s):  
Rafael Castro-Triguero ◽  
Enrique Garcia-Macias ◽  
Erick Saavedra Flores ◽  
M.I. Friswell ◽  
Rafael Gallego
Keyword(s):  
Structural Model ◽  
Model Updating ◽  
Ambient Vibration ◽  
Scale Model ◽  
Structural Behavior ◽  
Modal Parameters ◽  
Content Type ◽  
Multi Scale ◽  
Ambient Vibration Tests ◽  
Vibration Tests

Purpose The purpose of this paper is to capture the actual structural behavior of the longest timber footbridge in Spain by means of a multi-scale model updating approach in conjunction with ambient vibration tests. Design/methodology/approach In a first stage, a numerical pre-test analysis of the full bridge is performed, using standard beam-type finite elements with isotropic material properties. This approach offers a first structural model in which optimal sensor placement (OSP) methodologies are applied to improve the system identification process. In particular, the effective independence (EFI) method is used to determine the optimal locations of a set of sensors. Ambient vibration tests are conducted to determine experimentally the modal characteristics of the structure. The identified modal parameters are compared with those values obtained from this preliminary model. To improve the accuracy of the numerical predictions, the material response is modeled by means of a homogenization-based multi-scale computational approach. In a second stage, the structure is modeled by means of three-dimensional solid elements with the above material definition, capturing realistically the full orthotropic mechanical properties of wood. A genetic algorithm (GA) technique is adopted to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally. Findings An overall good agreement is found between the results of the updated numerical simulations and the corresponding experimental measurements. The longitudinal and transverse Young's moduli, sliding and rolling shear moduli, density and natural frequencies are computed by the present approach. The obtained results reveal the potential predictive capabilities of the present GA/multi-scale/experimental approach to capture accurately the actual behavior of complex materials and structures. Originality/value The uniqueness and importance of this structure leads to an intensive study of its structural behavior. Ambient vibration tests are carried out under environmental excitation. Extraction of modal parameters is obtained from output-only experimental data. The EFI methodology is applied for the OSP on a large-scale structure. Information coming from several length scales, from sub-micrometer dimensions to macroscopic scales, is included in the material definition. The strong differences found between the stiffness along the longitudinal and transverse directions of wood lumbers are incorporated in the structural model. A multi-scale model updating approach is carried out by means of a GA technique to calibrate the micromechanical parameters which are either not well-known or susceptible to considerable variations when measured experimentally.

Bayesian model updating of a 20-story office building utilizing operational modal analysis results

2019 ◽  
Vol 22 (16) ◽  
pp. 3385-3394
Author(s):  
Heung Fai Lam ◽  
Jun Hu ◽  
Mujib Olamide Adeagbo
Keyword(s):  
Bayesian Model ◽  
Structural Model ◽  
Model Updating ◽  
Dynamic Properties ◽  
Ambient Vibration ◽  
Modal Parameters ◽  
Vibration Test ◽  
Ambient Vibration Test ◽  
Building Model ◽  
Shear Building

Most existing buildings are not equipped with long-term monitoring system. For the structural model updating and damage detection of this type of structures, ambient vibration test is popular as artificial excitation is not required. This article presents in detail the full-scale ambient vibration test, operational modal analysis, and model updating of a tall building. To capture the dynamic properties of the target 20-story building with limited number of sensors, a 15-setup ambient vibration test was designed to cover at least three measurement points (each consists of a vertical and two orthogonal horizontal measured degrees of freedom) for each selected floor. The modal parameters of each setup were extracted from the measured acceleration signals using a frequency domain decomposition method and were combined to form the global mode shape through the least-squares method. Due to the regularity of the building, a simple class of shear building models was employed to capture the dynamic characteristics of the building under lateral vibration. The identified modal parameters of the building were employed for the model updating of the shear building model to identify the distribution of inter-story stiffness. Since the “amount” of the measured information is small when compared to the “amount” of required information for identifying the uncertain parameters, the model updating problem is unidentifiable. To handle this problem, the Markov chain Monte Carlo–based Bayesian model updating method is employed in this study. The identified modal parameters revealed interesting features about the dynamic properties of the building. The well-matched results between model-predicted and identified modal parameters show the validity of the shear building model in this case study. This study provides valuable experience in the area of structural model updating and structural health monitoring.

Modal parameter identification of a long-span footbridge by forced vibration experiments

2017 ◽  
Vol 20 (5) ◽  
pp. 661-673 ◽  
Author(s):  
Q Wen ◽  
XG Hua ◽  
ZQ Chen ◽  
JM Guo ◽  
HW Niu
Keyword(s):  
Free Vibration ◽  
Frequency Response ◽  
Forced Vibration ◽  
Ambient Vibration ◽  
Modal Parameters ◽  
Response Functions ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Cable Stayed Bridge ◽  
Vibration Tests

Performing forced vibration tests on full-scale structures is the most reliable way of determining the relevant modal parameters in structural dynamics, such as modal frequencies, mode shapes, modal damping, and modal masses. This study describes the modal identification of a double-level curved cable-stayed bridge with separate deck systems for pedestrians and vehicles via forced vibration tests. The steady-state structural responses to sinusoidal excitations produced by an electrodynamic shaker are recorded under varying excitation frequencies, and the frequency response functions are established. The measured frequency response functions are curve fitted to estimate the modal parameters. The numerical simulation of frequency response function–based modal parameter identification of an elastically multi-supported continuous beam structure is carried out, and the emphasis has been placed on the evaluation of the effect of an additional shaker mass, excitation frequency step and range, multi-mode vibration, and noise on identification results. Finally, the modal parameters for the first lateral mode of a double-level curved cable-stayed bridge are identified by forced vibration experiments, and the results are compared with those from ambient vibration tests and free vibration tests. The effect of the unmeasured wind excitation on identification is discussed. It is shown that the effect of ambient vibration is minor for wind velocity of 3–5 m/s. The damping ratios identified by forced and free vibration tests are comparable, while those from ambient vibration are subject to large variations. The modal mass obtained from forced vibration tests is in good agreement with finite element prediction, which provides design basis for mass-type dampers.

Sign in / Sign up

Export Citation Format

Share Document