Sharif Digital Repository

Today, by emerging wearable technologies and digital health, it is possible to constantly monitor vital signals of people without time-consuming and costly referrals to medical centers. Applications of wearable sensors for health monitoring include electrocardiograms (ECG), blood pressure measurement, and blood sugar measurement, etc. One of the important fields of health monitoring is cardiac arrhythmia detection. Cardiac arrhythmia is any kind of anomalies in heart beat rhythm that can lead to serious damage to vital organs of the body. It is estimated that between 750 thousand to 1.5 million people are facing cardiac arrhythmia in Iran. Therefore, early detection of cardiac arrhythmia is... 

Damage and collapse in structural systems due to structural loads are considered as a threat to human lives. Therefore, using structural health monitoring methods in order to estimate structural damages and preventing structural collapse, have drawn a lot of attention. Due to the importance of considering random vibration, a nondestructive damage detection method using power spectral density function has presented in this study. This method is based on model updating and solving the sensitivity equations and it is also a model based method. The mentioned method can be classified as a vibration-based health monitoring method in frequency domain which includes dynamic excitation in some... 

Pipeline systems are one of the cheapest ways for distribution and transportation of petroleum and natural gas. The testing of pipes used in the petroleum industry is necessary to avoid unplanned process interruptions, environmental pollution and provide good safety. One of the methods which is used for pipeline inspection is the ultrasonic non-destructive testing (NDT) technique. The use of conventional NDT techniques such as ultrasonic thickness gauging is a slow inspection process, which becomes very expensive when full inspection is needed. Ultrasonic guided waves provide an appropriate fast screening technique. These waves stress the whole pipe wall and propagate along the length of the... 

Damage detection by Piezoelectric Wafer Active Sensors is one of the emerging efficient and dominant Structural Health Monitoring (SHM) methods. These sensors assess the health state of the structure due two strategies: a) near-field damage detection, b) far-field damage detection. The far-field damage detection is based on the high frequency Lamb wave propagation. As wave travels in a damaged structure, phase and amplitude of the wave will be changed. So comparison of the received signal from the pristine structure with damaged structure can give useful information about the health state of the structure. As PWAS is the essential part of this method, simulation and modeling of this sensors... 

Cost-effective and reliable damage detection is critical for utilization of composite materials. This research investigates a wavelet-based approach for SHM and detection of through-thickness crack in different lengths and angles in [0/45/-45/90]s CF/EP composite plate utilizing ANSYS finite element method (FEM) software and digital signal processing technique utilizing MATLAB software. To this end, a dual-PZT actuation scheme is applied, aimed at generating the S0 mode at a square composite plate. This study contributes to the damage detection by developing an improved wavelet-based signal processing technique that enhances the visibility and interpretation of the Lamb wave signals related... 

In the regard of structural health monitoring the identification of the structural modal parameters is essential. Since the different sources (wind, waves, Devices …) induce vibration on an offshore platform, it is impossible to determine the portion of each source in vibration. Thus the methods that analyze vibrations needless of input measurements are more efficient. These methods apply the ambient factors and obtain the modal properties from the structural response. This procedure has no unwanted effect on the serviceability of structure and by placement of sensors on the platform; one can monitor the structural health.
In the present work a two dimensional jacket offshore platform... 

In this study, damage detection of brick masonry walls using a unique signal processing technique has been addressed. Firstly, the pushover analysis and the calibration of the model is performed. Then, the dynamic analysis of the wall under earthquake excitation in three cases with different aspect ratios is conducted. Finally the dynamic properties of the system, namely natural frequency and modal damping ratio, are identified using continuous wavelet transform. The advantage of wavelet transform is its fine time-frequency resolution. The Morlet mother wavelet is used since it can provide the best time-frequency resolution based on Heisenberg uncertainty principle. Afterwards, the... 

High construction and installation costs of offshore platforms, and also harsh environments in which they operate, make health monitoring of these structures more important. Conventional methods to solve the health monitoring problem are deterministic, whereas much uncertainties are imposed to the problem. In most methods of health monitoring methods we try to identify natural frequencies and mode shapes of structures by using its dynamic response. This set of data is then compared to results of modal analysis performed on a finite element model of structure in order to detect any possible damage. In deterministic methods each response of structure is pertained to one damage state, in a... 

Structural Health Monitoring (SHM) is a multidisciplinary emerging research field. SHM assesses the health state of the structure through processing and interpreting of signals and can predict remain life of the structure. Damage detection with Piezoelectric Wafer Active Sensors (PWAS) is one of the effective and emerging methods of SHM. One of the most critical parts of aerial structures is lap joints in which SHM could be very effective. In this research, damage detection of lap joints using lamb wave propagation has been studied. A 3D model of an aluminum lap joint presented. The PWAS are modeled separately and bonded to the host structure and coupled electromechanically with the... 

Nowadays, the structural health monitoring is considered as an essential element in improving the performance of the structures. The role and importance of the issues in this area have been reached to the point that different ideas and policies are developed for the safety margin over the useful life of the structures. To analyze more accurately, a real model of a turbine blade is required. This issue would be taken into more consideration when the scale of the turbine gets larger. Changing of the design philosophies over time results in effective changes in the design process and maintenance procedures. Any single of these inspections has different importance according to users' demands. In... 

Performance of civil infrastructures, such as high-rise buildings, bridges, tunnels, offshore platforms and other structures may be critically influenced by existence of structural damages or even lead to devastating consequences. Structural Health Monitoring(SHM) and damage detection denotes the ability to monitor the performance of structure, detect and assess any damage at the earliest stage in order to reduce the life-cycle cost of structure and improve its reliability and safety. Generally, damage is defined as some changes in the physical properties of a structure, such as stiffness matrix. On the other hand, presence of damage causes changes in structural dynamic characteristics, such...