scholarly journals Model Bridge Span Traversed by a Heavy Mass: Analysis and Experimental Verification

2021 ◽  
Vol 6 (9) ◽  
pp. 130
Author(s):  
Georgios I. Dadoulis ◽  
George D. Manolis
Keyword(s):  
Transient Response ◽  
Structural Damage ◽  
Dynamic Properties ◽  
Classical Problem ◽  
Highway Bridges ◽  
Free Vibrations ◽  
Primary System ◽  
Implicit Assumption ◽  
Bridge Span ◽  
Civil Engineering Infrastructure

In this work, we investigate the transient response of a model bridge traversed by a heavy mass moving with constant velocity. Two response regimes are identified, namely forced vibrations followed by free vibrations as the moving mass goes past the far support of the simply supported span of the bridge. Despite this being a classical problem in structural dynamics, there is an implicit assumption in the literature that moving loads possess masses that are at least an order of magnitude smaller than the mass of the bridge span that they traverse. This alludes to interaction problems involving secondary systems, whose presence does not alter the basic characteristics of the primary system. In our case, the dynamic properties of the bridge span during the passage of a heavy mass change continuously over time, leading to an eigenvalue problem that is time dependent. During the free vibration regime, however, the bridge recovers the expected dynamic properties corresponding to its original configuration. Therefore, the aim here is the development of a mathematical model whose numerical solution is validated by comparison with experimental results recovered from an experiment involving a scaled bridge span traversed by a rolling mass. Following that, the target is to identify regions in the transient response of the bridge span that can be used for recovering the bridge’s dynamic properties and subsequently trace the development of structural damage. In closing, the present work has ramifications in the development of structural health monitoring systems applicable to critical civil engineering infrastructure, such as railway and highway bridges.

Dynamic Property Evaluation of a Long-Span Cable-Stayed Bridge (Sutong Bridge) by a Bayesian Method

2018 ◽  
Vol 19 (01) ◽  
pp. 1940010 ◽  
Author(s):  
Yan-Chun Ni ◽  
Qi-Wei Zhang ◽  
Jian-Feng Liu
Keyword(s):  
Natural Frequency ◽  
Dynamic Characteristics ◽  
Structural Damage ◽  
Dynamic Properties ◽  
Modal Identification ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Sutong Bridge

Modal identification aims at identifying the dynamic properties including natural frequency, damping ratio, and mode shape, which is an important step in further structural damage detection, finite element model updating, and condition assessment. This paper presents the work on the investigation of the dynamic characteristics of a long-span cable-stayed bridge-Sutong Bridge by a Bayesian modal identification method. Sutong Bridge is the second longest cable-stayed bridge in the world, situated on the Yangtze River in Jiangsu Province, China, with a total length of 2 088[Formula: see text]m. A short-term nondestructive on-site vibration test was conducted to collect the structural response and determine the actual dynamic characteristics of the bridge before it was opened to traffic. Due to the limited number of sensors, multiple setups were designed to complete the whole measurement. Based on the data collected in the field tests, modal parameters were identified by a fast Bayesian FFT method. The first three modes in both vertical and transverse directions were identified and studied. In order to obtain modal parameter variation with temperature and vibration levels, long-term tests have also been performed in different seasons. The variation of natural frequency and damping ratios with temperature and vibration level were investigated. The future distribution of the modal parameters was also predicted using these data.

A Comparative Study of Mass Based Vibration Dampers

2017 ◽  
Author(s):  
Mohamed Gharib ◽  
Mansour Karkoub
Keyword(s):  
Comparative Study ◽  
Passive Control ◽  
Initial Conditions ◽  
Free Vibrations ◽  
Decay Rates ◽  
Coupled Systems ◽  
Primary System ◽  
Operating Personnel ◽  
Control Techniques ◽  
Dynamic Structures

Undesired vibrations in structures, buildings, and machines lead to reduction in the life of the system and greatly affects the safety of the occupying or operating personnel. In addition, economic and time losses could result from needed repairs or reconstruction. Many control techniques, active and passive, have been devised over the years to reduce/eliminate the vibrations in the aforementioned systems. Passive vibration control techniques are favorable over the active ones due to their simplicity, ease of implementation, cost, and power consumption. In dynamic structures, such as large buildings, passive control techniques are favored over their active counterparts. The most common types of passive control devices are tuned mass and impact dampers. The advocates of each of these devices boasts advantages of the others; however, there have been no systematic studies to compare and quantify the effectiveness of each of these types of devices as well as their suitability for specific applications. In this paper, a comparative study between the tuned mass dampers and impact dampers is conducted. A one-story structure is used to show the effectiveness of each of these devices in absorbing the vibrations of the structure. The coupled systems are modeled and simulated under free vibrations. The time responses are acquired using the same geometric parameters, excitation, and initial conditions. The comparisons are based on the settling time and amplitude decay rates of the primary system using each damper type. The numerical results show that both dampers can produce similar dampening effects if the parameters are optimized; however, correlating the dampers parameters is a challenging problem in the field of vibration and control.

Analysis of a damaged 12-storey frame-wall concrete building during the 2010 Haiti earthquake — Part II: Nonlinear numerical simulations

2013 ◽  
Vol 40 (8) ◽  
pp. 803-814 ◽  
Author(s):  
Benoit Boulanger ◽  
Patrick Paultre ◽  
Charles-Philippe Lamarche
Keyword(s):  
Structural Damage ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Shear Walls ◽  
Element Model ◽  
Companion Paper ◽  
Ambient Vibration ◽  
Wall Structure ◽  
Haiti Earthquake ◽  
Concrete Building

After the 2010 Haiti earthquake, which destroyed a significant part of the seismically vulnerable city of Port-au-Prince, the country’s capital, a 12-storey reinforced concrete building that behaved well was investigated to understand its dynamic response. This paper completes the experimental work presented in a companion paper, in which the dynamic properties of the building were obtained from ambient vibration tests, and from which a finite-element model was updated. This paper’s main objectives are: (i) to understand the causes that led to the observed structural damage; and (ii) to estimate the likely seismic excitation at the site of the building. Several nonlinear analyses involving various ground motion intensities were conducted and the results were compared with the damage reported during the on-site survey. The numerical models reproduced the observed damages well and helped to explain them. The overall response of the mixed stiff frame–wall structure was clearly dominated by the high stiffness of the shear walls, showing that this type of structural system helps in keeping reasonable interstorey drift levels. Overall, the building’s structure seems to have responded linearly to all the ground motions investigated, but deformation demands imposed to the frame by the shear walls lead to local damages.

scholarly journals The bridge dynamic properties monitoring

2019 ◽  
Vol 265 ◽  
pp. 03009
Author(s):  
Jozef Melcer ◽  
Daniela Kuchárová ◽  
Gabriela Lajčáková
Keyword(s):  
Dynamic Properties ◽  
Experimental Testing ◽  
Experimental Measurements ◽  
Loading Test ◽  
Steel Cable ◽  
Cable Stayed Bridge ◽  
Bridge Span ◽  
Water Side ◽  
The Right

The SNP Bridge over the Danube in Bratislava represents an attractive steel cable-stayed bridge. Its length is 431.8 m. The submitted paper describes the methodology of experimental testing and presents some results of the loading test. During this test it was observed that the dilatation unit on the right water side shows some failure. Due to this failure the dilatation unit acts as a generator of vibration of the end bridge span. On the basis of experimental measurements this failure was detected and the dilatation unit was renovated.

Seismic Structural Damage Detection Based on Time Frequency Response Function

2011 ◽  
Vol 219-220 ◽  
pp. 243-249
Author(s):  
Bai Sheng Wang ◽  
Lie Sun ◽  
Zhi Wei Chang
Keyword(s):  
Frequency Response ◽  
Response Function ◽  
Structural Damage ◽  
Frequency Response Function ◽  
Dynamic Properties ◽  
Response Analysis ◽  
Central Frequency ◽  
Structural Dynamic ◽  
Time Frequency ◽  
Marginal Spectrum

Considering that Hilbert-Huang Transformation (HHT) can be used to analyze instantaneous frequency in structural dynamic analysis, this paper proposes the concept of HHT marginal spectrum based time frequency response function. It also defines “central frequency”, which is used to reflect the change of structural dynamic properties during earthquakes, and discloses time-varying development of seismic structural damage. Using a three-story shear frame model, which is subjected to the El Centro seismic wave, the HHT time frequency response analysis of its acceleration response has been made, results show that the adoption of central frequency can successfully indicate the damage inception instant and its development.

scholarly journals FINITE ELEMENT MODEL OF DYNAMIC TRAIN-BRIDGE INTERACTION

2020 ◽  
Vol 22 (6) ◽  
pp. 154-166
Author(s):  
S. V. Efimov ◽  
K. O. Zhunev
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Dynamic Properties ◽  
Accumulation Rate ◽  
Dynamic Stiffness ◽  
Oscillation Amplitude ◽  
Element Model ◽  
Operating Conditions ◽  
Railway Bridges ◽  
Bridge Span

Innovative heavy wagons with a 25–27 tf axle load and the freight train movement organization having a higher weight and length are being put into operation in Russia. New operating conditions of railway bridges require an assessment of bearing capacity, durability, accumulation rate of fatigue damage and reliability. The important parameters are the dynamic properties of railway bridges (frequencies and modes of natural vibrations, decay rate, dynamic stiffness).The aim of this work is to determine the dynamic interaction of trains having different structure, weight and length with a railway bridge using numerical modeling in the midas Civil bridge software. The proposed model is verified by the dynamic parameters of spans (natural vibration frequencies), which are determined during the bridge inspection using a Tensor-MS system.The modal analysis is given to the finite element model. The lowest natural modes of the bridge are determined. Based on numerical simulation of the interaction between the train and the bridge unfavorable speed of trains is calculated leading to an increase in the oscillation amplitude of the bridge span as well as in the bridge dynamic coefficient with regard to the design features of the train structure and composition.

Pulsed Eddy Current Response to General Corrosion in Concrete Rebar

2020 ◽  
Vol 3 (4) ◽  
Author(s):  
Ian Eddy ◽  
P. R. Underhill ◽  
J. Morelli ◽  
T. W. Krause
Keyword(s):  
Transient Response ◽  
Exponential Decay ◽  
Eddy Current ◽  
Structural Integrity ◽  
Concrete Structures ◽  
Highway Bridges ◽  
General Corrosion ◽  
Current Response ◽  
Pulsed Eddy Current ◽  
Long Time

Abstract Corrosion of carbon steel rebar in concrete structures, such as highway bridges and buildings, has a direct impact on their structural integrity since the rebar provides the tensile strength within the structure. Rebar strength depends on the remaining effective radius of a given rod. Long-time decay up to 0.1 s, in the transient response of pulsed eddy current (PEC), was examined as a potential method to quantify general corrosion in ferromagnetic rebar. The transient response of a coaxial solenoidal drive–receive coil pair, oriented parallel to the rebar axis, was analyzed over a range of distances into the concrete (liftoff) and rebar radii. At long times, the single exponential decay constant was largely independent of liftoff. A power law relationship for the characteristic decay time, consistent with long-time diffusion of electromagnetic fields into a rod, was observed. The intercept of a best-fit line to measured voltage decay decreased exponentially with liftoff and maintained a measurable response up to 110 mm distance for a 25 mm (1 in.) diameter rebar. This exponential decay was present in 22 mm (7/8 in.), 19 mm (3/4 in.), and 15 mm (5/8 in.) samples as well. Reported results demonstrate the potential for PEC to quantify remaining cross-sectional area of rebar in concrete structures.

Dynamic characteristics of Canada's Parliament Hill towers from ambient vibrations and recorded earthquake data

2021 ◽  
Vol 48 (1) ◽  
pp. 16-25
Author(s):  
Michal Kolaj ◽  
John Adams
Keyword(s):  
Structural Damage ◽  
Nonlinear Response ◽  
Dynamic Properties ◽  
Ground Motions ◽  
Ambient Vibration ◽  
The South ◽  
Vibration Data ◽  
South West ◽  
Baseline Values ◽  
Strong Ground

The dynamic properties of Parliament Hill’s buildings (Ottawa, Canada) are of particular interest due to their important heritage value and because of the seismic retrofit project currently underway. To measure the dynamic properties directly, ambient vibration data were collected within the Peace Tower of Centre Block and the South-West Tower of East Block and processed together with weak to strong ground motions from six earthquakes. Both datasets found the fundamental mode to be 1.0–1.15 Hz for the Peace Tower and 2 Hz for the South-West Tower. The 2010 magnitude 5 Val-des-Bois earthquake induced peak accelerations of 49% g and 18% g in the top floors of the Peace and South-West towers, respectively, triggering a nonlinear response, causing the frequencies of the dominant modes to be reduced by 10%–15%. The reduction in frequency was temporary and the frequencies returned to baseline values, suggesting that there was no permanent structural damage.

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