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damage-detection
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Total 127 records
Condition Assessment and Damage Detection in Concrete Structures Using Computer Vision-Based Deep Learning Techniques
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
The ultimate goal of this study is to evaluate the condition of concrete structures using computer vision methods and using powerful tools such as machine learning methods based on visual information. This assessment is performed by detecting damage in these structures. With the aging of structures such as dams, bridges and tall buildings, structural health monitoring is an important task in ensuring their safety and stability. Therefore, rapid assessment of the health of structures and diagnosis of damage after destructive events is of great value in terms of providing resilience of structures. Visual inspection of structures by experts is one of the basic methods of evaluating structures....
Detection of Damage Location in Two-way Slabs Using Structural Vibration Modes with Wavelet Transform
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor)
Abstract
This study aimed to develop a method for locating damages in the early stages of damage expansion in plate components of the structure using a one-dimensional discrete wavelet function. Continuous monitoring of the health of structures to preserve and repair them to protect the lives and property of individuals and national capitals and to lower the direct and indirect economic costs imposed on society is vital and inevitable for society's decision-makers. Because the damage to the structure caused by earthquakes occurring during the lifetime of the structure, exhaustion of structural components, improper implementation of the structure at the time of construction, and other events that...
Damage Identification in Structures with Lamb Waves and Optimal Sensor Layout Designing
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
This study presents the best layout with optimal number of sensors for an arbitrary monitoring area based on reference free damage detection and localization. In recent years, damage detection approaches with the concept of instantaneous baseline measurements in Structural Health Monitoring (SHM) with lamb wave propagation are being developed. An array of spars transducers is obligatory in SHM with lamb wave propagation, so that designing the best one is a concern for many researchers. To obtain the best sensors layout, damage localization process should be done for all definable sensors layouts in many different crack positions. Obviously, doing this seems not practical as wave propagation...
Damage Localization and Quantification Assessment in Structures Using Probabilistic Model Updating
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Ali (Supervisor)
Abstract
This research focuses on probabilistic damage detection in the finite element model by using an application of Bayes' inference rule. Density and elastic modulus are sources of uncertainties in structures, therefore the probabilistic method is chosen instead of deterministic. According to the test's data, the distribution of density and elastic modulus have been updated. Then through Bayes' rule the probability of each damage state updates by modal data. Damage states are defined through a coefficient between 0-1 by multiplying to the inertia of elements of the structure. After each observation, the posterior probabilities are updated and this process happens through the multiplication of...
Structural Health Monitoring for Frame Structure Using Artificial Neural Networks (ANNS)
, M.Sc. Thesis Sharif University of Technology ; Mofid, Masoud (Supervisor)
Abstract
Structural Health Monitoring (SHM) is an effective method for the early detection of structural damage, and this method can reduce the maintenance costs of structures. In this thesis, the use of artificial one-way and multi-layer artificial neural network is evaluated to determine the damage to the structure. The neural network method used in this thesis is a post-propagation method. Finally, the numerically damage determine will be evaluated using a two-dimensional frame structure and a three-dimensional frame structure by finite element method. In this method, the dynamic properties of the structure are used only in the form of the modules. For this purpose, the finite element model is...
Structural Damage Detection by Using Signal-Based and Artificial Intelligence Methods; Case Study 'Moment-Resisting Frame Structure
, M.Sc. Thesis Sharif University of Technology ; Bakhshi, Amin (Supervisor) ; Bahar, Omid (Supervisor)
Abstract
Civil structures are on the verge of changing which leads energy dissipation capacity to decline. Structural Health Monitoring (SHM) as a process in order to implement a damage detection strategy and assess the condition of structure plays a key role in structural reliability. Earthquake is a recognized factor in variation of structures condition, inasmuch as inelastic behavior of a building subjected to design level earthquakes is plausible. In this study Hilbert Hunag Transformation (HHT) is superseded by Ensemble Empirical Mode decomposition (EEMD) and Hilbert Transform (HT) together. Albeit this method is closely resemble HHT, EEMD brings more appropriate Intrinsic Mode Functions (IMFs)....
Crack Localisation In Homogeneous Plates by Analyzing the Dynamic Responses of the Plate Excited by the Moving Load
, M.Sc. Thesis Sharif University of Technology ; Mofid, Massoud (Supervisor) ; Nikkhoo, Ali (Co-Supervisor)
Abstract
The purpose of the study: The purpose of this study is to identify the crack position in homogeneous plates through health monitoring methods based on vibration. Identifying structural damage is one of the issues that attention can prevent the sudden collapse of structures and causing heavy loss of life and property. For this reason, extensive studies have been conducted in this field in recent decades. In this study, plates are examined as one of the most used structural members, and their damage is identified through a proposed method based on wavelet transform. Research method: In this study, through the wavelet transform method, the dynamic responses of a homogeneous plate excited by a...
Identification of Damage Type and Location in Reinforced Concrete Piers of Slab– Beam Bridges Using Numerical Methods
, M.Sc. Thesis Sharif University of Technology ; Ahmadizadeh, Mahdi (Supervisor)
Abstract
Bridges are among the crucial elements of transportation networks, and play an important role in facilitating emergency relief efforts following earthquakes. For this reason, it is emparative to monitor their damages to ensure about their performace in earthquakes. The structure of a bridge is divided into two parts, namely the superstructure and substructure. Due to the relatively high rigidity and strength of superstructures, most of structural damage is usually concentrated in substructures, which may ultimately affect the overall stability of the bridge. Therefore, assessing the level of damage in the substructure is of utmost concern. This research attempts to evaluate the damage in the...
Damage Detection in Plate using Wave Propagation Method
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Structural health monitoring (SHM) has been motivated in aircraft and civil industries over the two last decades. Ultrasonic guided wave propagation technique is one of the best damage detection methods in airplane thin wall structures because of their large distance traveling and low attenuation.
In fact by efficient design of sensors pattern one can effectively pick up the changes that happen in propagated signals due to presence of any kind of structural damage. This could be effectively achieved by numerical simulation techniques like finite element modeling. To obtain a damage detection algorithm based on instantaneous baseline data, here, finite element technique is employed for...
In fact by efficient design of sensors pattern one can effectively pick up the changes that happen in propagated signals due to presence of any kind of structural damage. This could be effectively achieved by numerical simulation techniques like finite element modeling. To obtain a damage detection algorithm based on instantaneous baseline data, here, finite element technique is employed for...
Determining Location and Estimating Severity of Damage Using Sensitivities of Principal Components of Frequency Response Functions
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofouei, Fayyaz (Supervisor) ; Esfandiari, Akbar (Supervisor)
Abstract
Principal component analysis (PCA) is a conventional tool for dynamic system analysis. In this paper, a new damage diagnosis method is presented based on sensitivities of principal components obtained from PCA of Frequency response functions (FRFs). Damage identification, determination of its location and estimation of the damage severity are conducted by an innovative well established sensitivity relation of PCA results. Then, sensitivity matrix is obtained by using measured frequency of damaged structure, and comparison of PCA of the intact structure with PCA from FRFs which are measured at sensors locations. Damage location and its severity are calculated by model updating procedure. This...
“Damage Detection and Localization with Wavelet Transformation of Response Accelerations of a Shear Building under Seismic Records Via Deep Learning”
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
The main goal of this research is detection, localization, and determining the severity of structural damages. The importance of this objective is to prevent abrupt destruction and severe human and financial losses. Damage detection is divided into local and global detection, and global detection contains static and vibration-based methods. In this research, the vibration-based method is used. Due to the complexity of this method, accurate and powerful tools are required for detecting effective features in damages; Deep Learning (DL), which is part of a broader family of machine learning methods based on artificial neural networks (ANN), could be used. Accordingly, in this project, the...
Data-driven Damage Assessment of Reinforced Concrete Shear Walls Using Visual Features of Damage
, M.Sc. Thesis Sharif University of Technology ; Mohtashm Dolatshahi, Kiarash (Supervisor)
Abstract
This research proposes a damage assessment framework based on the visual features of a damaged reinforced concrete shear wall, such as crack pattern distribution, crushing areal density, aspect ratio, and the presence of the boundary condition. The study contains two parts: identifying the performance level of the damaged walls (i.e., Immediate Occupancy, Life Safety, and Collapse Prevention) and estimating the residual strength and drift ratio of the walls. The research database contains 236 images of 72 reinforced concrete shear walls tested in the laboratory under the quasi-static cyclic loadings at various drift ratios between 0.0 to 4.0. To identify the performance level of a damaged...
Detection of Abrupt Changes in Structural Properties Through Vibration Signal Processing
, Ph.D. Dissertation Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Structural system identification from vibration data is one of the most interesting research topics in the structural health monitoring area. Recently, realization and detection of the effects of damage when a structure is subjected to strong ground motion has become a great concern in earthquake and structural engineering communities. Seismic signal processing is one of the most reliable methods of detecting the structural damage during earthquakes. The structural responses during earthquakes are nonstationary with respect to both amplitude and frequency. The state-of-the-art time-frequency distributions when applied to vibration records were studied. Different methods of analysis for...
Structural Health Monitoring of Beam with Symmetric Discontinuity Using Ultrasonic Guided Wave Propagation
, M.Sc. Thesis Sharif University of Technology ; Behzad, Mehdi (Supervisor) ; Mirdamadi, Hamid Reza (Co-Advisor)
Abstract
Damage identification in uniform structures using Lamb waves has been studied by the researchers; however, as most of the industrial structures are not uniform, it is necessary to study more complex structures. In this thesis, a method of identifying notch specifications as damage in a symmetric stepped beam with arbitrary number of steps using Lamb wave propagation is presented. Initially, the study will examine and compare the Lamb wave propagation in uniform, symmetric stepped and asymmetric stepped beams. In the first stage, a method for detection of damage location in symmetric stepped beam is presented. This method is based on mode conversion phenomenon of Lamb wave modes. Moreover,...
Vibration Based Health Monitoring for Damage Detection of Composite Laminates
, M.Sc. Thesis Sharif University of Technology ; Zabihollah, Abolghasem (Supervisor)
Abstract
Development of composite materials is one of the boldest technological advances of the last half of the twentieth century. This is due to their specific characteristics mostly considerably high strength-to-weight ratio, compared to metals and their highly customizing properties for different applications which make them a suitable material to be used in variety of domain from aerospace and automobiles to medical and sport equipments. Multi-stable asymmetrical laminates and non-uniform thickness laminated composite beams are being used as structural elements in a wide range of advanced engineering applications. Multi-stable asymmetrical laminates can be snapped between two or more geometries...
Bayesian Model Class Selection and Peobabilistic System Identification Considering Model Complexity
, M.Sc. Thesis Sharif University of Technology ; Mahsuli, Mojtaba (Supervisor)
Abstract
This research proposes a Bayesian model selection framework using the stochastic filtering for rapid Bayesian identification of structures under seismic excitations. Structural identification after an earthquake at a regional scale entails a high computational effort. For rapid damage detection on a regional scale, using simplified and low-cost structural models is preferred over complex finite element models, due to the large amount of information needed for finite element modeling of numerous structures within a region as well as the high computational cost of such models. Timoshenko beams, shear beams, and shear buildings are examples of simplified structural models used in this study to...
Developing and Defining an Effective Approach for Detection of Multi-site Damage (MSD) in Metallic Aircraft lap Joint Skins
, Ph.D. Dissertation Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Today, considering the structural health monitoring system is approximately essential for aerospace structure due to more safety and reduction of maintenance costs. In this manner, aircraft designers and manufactures have recently attempted to usage of the monitoring system on their new products to maintain the superirority of them among the competitors. Furtheremore, installation of these systems on the aircraft will also becom one of the requirements of the aviation regulation in near future which must be complied.The lap joints are one of the major and inevitable components of the metallic airframe structure and the multisite damage such as fatigue cracks are the high probable damages...
Data Analysis for Damage Detection Using Machine Learning Algorithms
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
The pressurized structure such as aircraft fuselage and pipeline (in the oil and water transportation) have a great importance in today’s world. There is a growing tendency in improving design factors, safety and maintenance of such valuable structures. Change of design’s philosophy during the time from infinite life to safe damage and safe life and after that damage tolerance, are a process leading to many changes in design and consequently the methods of inspection, evaluation and maintenance. In this way, using old methods like non-destructive test and evaluation (NDT/E) is encountered with different problems when damage is tiny and there is no coincidence in examination (inspection)...
Evaluating two Model-Free data Interpertation Method for Measurments that are Influenced by Noise and Environmental Variations
, M.Sc. Thesis Sharif University of Technology ; Abedian, Ali (Supervisor)
Abstract
Interpreting data of infrastructures monitored to detect damage of a structural is one of the most challenging issues of structural health monitoring (SHM). Especially, when environmental factors such as temperature, wind and humidity affect the data and the situation become more complicated. In this study, two methods of analysis free model of moving principal components analysis (MPCA) and robust regression analysis (RRA) have recently been considered for monitoring infrastructures compared with a variety of methods of data interpretation and results are presented. In this study, the performance of different ways in different loading conditions and arrangement of sensors have been...
WT-SOBI Method Towards Blind System Identification of Structures
, M.Sc. Thesis Sharif University of Technology ; Kazemi , Mohammad Taghi (Supervisor)
Abstract
Blind source separation methods such as independent component analysis (ICA) and second order blind identification (SOBI) have shown considerable potential in the area of ambient vibration system identification. The objective of these methods is to separate the modal responses, or sources, from the measured output responses, without the knowledge of excitation. Several frequency domain and time domain methods have been proposed and successfully implemented in the literature. Whereas frequency-domain methods pose several challenges typical of dealing with signals in the frequency-domain, popular time domain methods such as NExT/ERA and SSI pose limitations in dealing with noise, low sensor...