Evaluation of the Lateral Vibration Response of Footbridges under Uncertainty Conditions

2022 ◽  
Author(s):  
Rocío García-Cuevas ◽  
Javier F. Jiménez-Alonso ◽  
Carlos Renedo M.C. ◽  
Francisco Martinez
Keyword(s):  
Distribution Function ◽  
Natural Frequency ◽  
Damping Ratio ◽  
Probabilistic Approach ◽  
Structural Response ◽  
Modal Parameters ◽  
Critical Number ◽  
Lateral Instability ◽  
Lateral Vibrations ◽  
Probabilistic Distribution

<p>The evaluation of the vibration performance of footbridges due to walking pedestrians is an issue of increasing importance in current footbridge design practice. The growing trend of slender footbridges with long spans and light materials has led to serviceability problems in lateral vibrations, which occur when the number of pedestrians reaches a “critical number”. Considering the mode of vibration in which the lateral instability is more likely to develop, the structural response depends on the modal characteristics of the footbridge; in particular, the natural frequency and the damping ratio. These modal parameters are stochastic variables, as it is not possible to determine them without a level of uncertainty. Thus, the purpose of this paper is to obtain the value of the lateral dynamic response of slender footbridges with a certain confidence level under uncertainty conditions. The uncertainties of those modal parameters are considered using a probabilistic approach. Both the natural frequency and the damping ratio are modelled as uncorrelated random variables that follow a predetermined probabilistic distribution function. Consequently, the structural response will also be described by a probabilistic distribution function, which can be estimated through Monte Carlo numerical simulations. As a result, the study allows the footbridge lateral response and the critical number of pedestrians to be calculated for different confidence levels and load scenarios, especially for crowd densities above the “critical number”.</p>

scholarly journals Influence of Crack on Modal Parameters of Cantilever Beam Using Experimental Modal Analysis

2018 ◽  
Vol 1 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Siva Sankara Babu Chinka ◽  
Balakrishna Adavi ◽  
Srinivasa Rao Putti
Keyword(s):  
Numerical Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Cantilever Beam ◽  
Damping Ratio ◽  
Crack Depth ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Crack Location

In this paper, the dynamic behavior of a cantilever beam without and with crack is observed. An elastic Aluminum cantilever beams having surface crack at various crack positions are considered to analyze dynamically. Crack depth, crack length and crack location are the foremost parameters for describing the health condition of beam in terms of modal parameters such as natural frequency, mode shape and damping ratio. It is crucial to study the influence of crack depth and crack location on modal parameters of the beam for the decent performance and its safety. Crack or damage of structure causes a reduction in stiffness, an intrinsic reduction in resonant frequencies, variation of damping ratios and mode shapes. The broad examination of cantilever beam without crack and with crack has been done using Numerical analysis (Ansys18.0) and experimental modal analysis. To observe the exact higher modes of beam, discretize the beam into small elements. An experimental set up was established for cantilever beam having crack and it was excited by an impact hammer and finally the response was obtained using PCB accelerometer with the help sound and vibration toolkit of NI Lab-view. After obtaining the Frequency response functions (FRFs), the natural frequencies of beam are estimated using peak search method. The effectiveness of experimental modal analysis in terms of natural frequency is validated with numerical analysis results. This paper contains the study of free vibration analysis under the influence of crack at different points along the length of the beam.

The Comparative Modal Analysis of Simulation and Experiment on the Electronic Button-Sewing Machine Shell

2013 ◽  
Vol 668 ◽  
pp. 612-615
Author(s):  
Li Zhang ◽  
Guang Yuan Nie ◽  
Hong Wu ◽  
Jie Chen
Keyword(s):  
Comparative Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Mode Shape ◽  
Damping Ratio ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Ansys Software ◽  
Sewing Machine ◽  
Simulation And Experiment

In this paper, the simulation with ANSYS software and the experimental modal analysis by impacting are carried out on the electronic button-sewing machine shell. The modal parameters, such as the natural frequency, the damping ratio and the mode shape, are obtained. Comparative analysis of their results shows that the mode shapes of the machine shell are mainly the outward-expanding and inward-contracting vibrations, which provides a useful reference for vibration and noise reduction of the electronic button-sewing machine.

Operational Modal Analysis of Broaching Machine

2012 ◽  
Vol 159 ◽  
pp. 170-175
Author(s):  
Lv Gao Lin ◽  
Shen Shun Ying ◽  
Shu Qiong Chen ◽  
Xiao Tian Lv
Keyword(s):  
Cutting Force ◽  
Natural Frequency ◽  
Fundamental Frequency ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Modal Parameters ◽  
Modal Shape ◽  
Modal Damping Ratio ◽  
Modal Damping ◽  
Cutting Velocity

Modal parameters for LG51SH broaching machine from operational responses are studied to examine the dynamic properties of mechanical structure. The operational modal is analyzed using PolyMAX method with responsive data of key point in broaching machine, which is excited in practical broaching operation and tested by LMS SCADAIII-105 system. The identified steady state modal, representative modal shape, modal damping ratio and natural frequency in broaching are presented. The test and analysis result shows that there are natural frequency of 38Hz and 192Hz, which are close to multiple of the fundamental frequency of cutting force in broaching, 6Hz, therefore, reasonable cutting velocity should be adopted to void producing fundamental frequency of cutting force in broaching.

scholarly journals The use of modal parameters in structural health monitoring

2018 ◽  
Vol 162 ◽  
pp. 04020
Author(s):  
Ali Al-Ghalib ◽  
Fouad Mohammad
Keyword(s):  
Structural Health Monitoring ◽  
Natural Frequency ◽  
Health Monitoring ◽  
Damping Ratio ◽  
Reinforced Concrete Beams ◽  
Modal Testing ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Structural Health ◽  
Vibration Parameters

The concrete is liable to damage due to various stresses which compensate its adequacy and safety. The estimation of remaining strength in reinforced concrete beams when subjected to increased loading action utilizing vibration parameters is investigated. For this reason, three beams are loaded statically close to failure in various increasing load steps and then repaired. The beams are all of same dimensions, but are different in strength and range of defects introduced to each sample. Following each loading step, the experimental modal testing is utilized to collect the vibration parameters (natural frequency, damping ratio and mode shapes) of each beam when tested under free support boundary conditions. The use of vibration parameters for the purpose of damage identification are known to be an elaborate and lengthy process. On the other hand, they are successful for the structural health monitoring given that they are able to provide global on-site automated continuous monitoring. The paper features post analysis procedures for experimental modal measurements of three concrete samples to obtain and correlate the basic modal parameters (natural frequency, modal damping and mode shapes). The results of the extracted modal parameters and their combination are exploited in this research as quantified identification parameters. This paper concludes that modal parameters are successful in determining the location and quantity of structural degradation, when holistic approach considered through a system.

Transmissibility Enhanced Inverse Chatter Stability Solution

2021 ◽  
pp. 1-41
Author(s):  
Yen-Po Liu ◽  
Yusuf Altintas
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Modal Parameters ◽  
Prediction Errors ◽  
Chatter Stability ◽  
Spindle Dynamics ◽  
Vibration Transmissibility ◽  
Inverse Stability ◽  
Artificial Neural Network Ann ◽  
Stability Limits

Abstract The structural dynamics of a machine tool at the tool center point characterizes its vibration response and machining stability which affects productivity. The dynamics are mostly dominated by the spindle-holder-tool assembly whose main vibration mode can change during machining due to centrifugal forces, thermal expansion, and gyroscopic moments generated at high spindle speeds. This paper proposes the identification of the spindle's in-process modal parameters: natural frequency, damping ratio and modal constant, by using a limited number of vibration transmissibility and critical chatter stability measurements. The classical inverse stability solution, which tunes the modal parameters to minimize prediction errors in chatter stability limits, is augmented with vibration transmissibility under two methods: (1) transmissibility-enhanced inverse stability solution: the modal parameters are updated to minimize prediction errors in chatter stability, and vibration transmissibility; (2) artificial neural network (ANN)-integrated inverse stability solution: the ANN uses vibration transmissibility to estimate the natural frequency and damping ratio, such that the inverse stability solution only needs to identify the modal constant. While both methods are experimentally validated, it is shown that the transmissibility-enhanced inverse stability solution is a more effective approach than the time-consuming ANN alternative for the estimation of in-process spindle dynamics.

scholarly journals On the Estimation of the Moving Mass of a TMD Installed on a Lively Structure

2021 ◽  
Vol 11 (10) ◽  
pp. 4712
Author(s):  
Alvaro Magdaleno ◽  
Cesar Pelaez ◽  
Alvaro Iglesias-Pordomingo ◽  
Antolin Lorenzana
Keyword(s):  
Natural Frequency ◽  
Damping Ratio ◽  
Structural Response ◽  
Degree Of Freedom ◽  
Moving Mass ◽  
Tuned Mass Dampers ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Modification Technique ◽  
One Step

Tuned Mass Dampers are devices which can be assimilated to single-degree-of-freedom systems with a certain amount of moving mass, a natural frequency and a damping ratio intended to be installed on lively structures to reduce the contribution of a certain mode to their response. Once placed on the structure, the movement of the mass damper couples to the structural response and determines its properties as an isolated system becomes challenging. The authors have previously presented a methodology to estimate the natural frequency and damping ratio of an SDOF system installed on a structure and not necessarily tuned to a certain mode. It was based on a transmissibility function and, thus, the moving mass could not be estimated. With this work, the authors go one step further and present a novel procedure to estimate the moving mass value by means of the same transmissibility function and two well selected frequency response functions. The methodology is applied to estimate the properties of a real single-degree-of-freedom system placed on a lively timber platform. The results are compared with the mass modification technique to show that the proposed methodology provides better estimations in a more efficient way.

Influence of the distribution of the shear walls on the seismic response of the buildings

2020 ◽  
Vol 15 (1) ◽  
pp. 37-44
Author(s):  
El Mehdi Echebba ◽  
Hasnae Boubel ◽  
Oumnia Elmrabet ◽  
Mohamed Rougui
Keyword(s):  
Structural Analysis ◽  
Seismic Response ◽  
Natural Frequency ◽  
Structural Design ◽  
Structural Response ◽  
Shear Walls ◽  
Structural Elements ◽  
Analysis Software ◽  
Ansys Apdl ◽  
The Impact

Abstract In this paper, an evaluation was tried for the impact of structural design on structural response. Several situations are foreseen as the possibilities of changing the distribution of the structural elements (sails, columns, etc.), the width of the structure and the number of floors indicates the adapted type of bracing for a given structure by referring only to its Geometric dimensions. This was done by studying the effect of the technical design of the building on the natural frequency of the structure with the study of the influence of the distribution of the structural elements on the seismic response of the building, taking into account of the requirements of the Moroccan earthquake regulations 2000/2011 and using the ANSYS APDL and Robot Structural Analysis software.

A validated robust and automatic procedure for vibration analysis of bridge structures using MEMS accelerometers

2020 ◽  
Vol 14 (3) ◽  
pp. 327-354
Author(s):  
Mohammad Omidalizarandi ◽  
Ralf Herrmann ◽  
Boris Kargoll ◽  
Steffen Marx ◽  
Jens-André Paffenholz ◽  
...  
Keyword(s):  
Vibration Analysis ◽  
Damping Ratio ◽  
Fem Analysis ◽  
Cost Effective ◽  
Analysis Procedure ◽  
Modal Parameters ◽  
Bridge Structure ◽  
Modal Damping ◽  
Mems Accelerometers ◽  
Better Than

AbstractToday, short- and long-term structural health monitoring (SHM) of bridge infrastructures and their safe, reliable and cost-effective maintenance has received considerable attention. From a surveying or civil engineer’s point of view, vibration-based SHM can be conducted by inspecting the changes in the global dynamic behaviour of a structure, such as natural frequencies (i. e. eigenfrequencies), mode shapes (i. e. eigenforms) and modal damping, which are known as modal parameters. This research work aims to propose a robust and automatic vibration analysis procedure that is so-called robust time domain modal parameter identification (RT-MPI) technique. It is novel in the sense of automatic and reliable identification of initial eigenfrequencies even closely spaced ones as well as robustly and accurately estimating the modal parameters of a bridge structure using low numbers of cost-effective micro-electro-mechanical systems (MEMS) accelerometers. To estimate amplitude, frequency, phase shift and damping ratio coefficients, an observation model consisting of: (1) a damped harmonic oscillation model, (2) an autoregressive model of coloured measurement noise and (3) a stochastic model in the form of the heavy-tailed family of scaled t-distributions is employed and jointly adjusted by means of a generalised expectation maximisation algorithm. Multiple MEMS as part of a geo-sensor network were mounted at different positions of a bridge structure which is precalculated by means of a finite element model (FEM) analysis. At the end, the estimated eigenfrequencies and eigenforms are compared and validated by the estimated parameters obtained from acceleration measurements of high-end accelerometers of type PCB ICP quartz, velocity measurements from a geophone and the FEM analysis. Additionally, the estimated eigenfrequencies and modal damping are compared with a well-known covariance driven stochastic subspace identification approach, which reveals the superiority of our proposed approach. We performed an experiment in two case studies with simulated data and real applications of a footbridge structure and a synthetic bridge. The results show that MEMS accelerometers are suitable for detecting all occurring eigenfrequencies depending on a sampling frequency specified. Moreover, the vibration analysis procedure demonstrates that amplitudes can be estimated in submillimetre range accuracy, frequencies with an accuracy better than 0.1 Hz and damping ratio coefficients with an accuracy better than 0.1 and 0.2 % for modal and system damping, respectively.

Output-Only Analysis for Modal Parameters Estimation of an Elastically Scaled Ship

2008 ◽  
Vol 52 (01) ◽  
pp. 45-56
Author(s):  
Giuliano Coppotelli ◽  
Daniele Dessi ◽  
Riccardo Mariani ◽  
Marcello Rimondi
Keyword(s):  
Life Prediction ◽  
Structural Response ◽  
Random Excitation ◽  
Parameters Estimation ◽  
Elastic Response ◽  
Modal Parameters ◽  
Practical Application ◽  
Scaled Model ◽  
Output Only ◽  
Ship Speed

The study of the ship structural response assumes an increasing importance as soon as the structures, characterized by much more lightness, are designed and built for faster vessels. This requisite implies a greater flexibility of the structures themselves, the elastic response of which has to be evaluated with accuracy in order to predict the dynamic behavior. In the present paper, a methodology for the identification of the modal parameters from the measurement of only the responses of a vibrating structure has been developed and applied to an elastically scaled model. This output-only technique is successfully applied to the segmented model of a real ship towed in the INSEAN linear basin. The broadband random excitation, provided by the loads exerted by an irregular sea pattern, induces a stochastic response of the model, which is monitored with accelerometers. The obtained results not only outline the parametric dependence of the modal properties on the ship speed, but also suggest a possible practical application of this technique for on-board structural monitoring and fatigue-life prediction.

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