Health monitoring allows small failures and damages to be identified and fixed before they turn into major and irreparable damages, to prevent loss of life and to make it possible to reinforce or improve it at the lowest cost. Currently, in the field of civil engineering, the health monitoring of structures is done in sensitive structures. One of the parts of the structure that may suffer initial damage before loading and during implementation due to difficulty in implementation is Concrete Filled Tube (CFT)columns.  One of the most likely damages in CFT columns is interface debonding damage. This damage causes the column to become weak and not benefit from the characteristics of steel and concrete together. Accordingly, in the present study, this damage and its severity in seismic (dynamic) parameters have been investigated. The results of the study show that damage causes changes in the MODE SHAPE of the structure, and it has caused a 6.38% reduction in the frequency in the first (main) MODE of the structure. Also, the damping of the damaged specimen is reduced by approximately 12% compared to the healthy specimen. On the other hand, the results show that the severity of damage is very effective in changing seismic parameters. So that by doubling the damage area, the frequency decreased by approximately 0.35% and reached from 873.27 Hz to 20.870.20 Hz, but the MODE SHAPE of damage did not affect the frequency

Flexural stiffness of a single load-induced crack is determined. Modal analysis is performed on the beam prior and after each load stage. MODE SHAPEs are extracted and eigenvectors used to determine the MODE SHAPE equations. Global flexural stiffness is derived by utilizing the regressed variable l and the local flexural stiffness is derived by applying the centered-finite-divided-difference formula on the regressed data. The global stiffness decreases with increasing severity of the crack. Results compared with values computed using the load-deflection plot showed similar trends. The algorithm may be used as a technique for detecting crack damage in reinforced concrete.

Much attention has been given to structural damage detection in recent decades in order to assess the reliability of structures during their service time. To detect damage in structures, one method, among different ones, is considered the most important i.e. the vibration-based methods. Because the modal parameters of structures like frequency and MODE SHAPE are so sensitive to structural properties like stiffness, it can therefore be used for detecting damage in structures. This paper presents a novel approach for structural damage detection and estimation using EXPANDED MODE SHAPEs and extreme learning machine (ELM). One of the problems in damage detection is the compatibility between the number of sensors and Degree of Freedoms (DOFs) in the finite element MODEl of structures, in which the number of sensors, installed to structure, is usually less than the number of DOFs in the finite element MODEl. So, the MODEl reduction method should be used to match incomplete measured MODE SHAPEs or the measured MODE SHAPEs should be EXPANDED to the dimension of the analytical MODE SHAPEs. In this study, the second option is adopted, using the improved reduction system (IRS) transformation matrix and used as input parameters to the ELM for damage identification. The proposed method uses the first two EXPANDED MODE SHAPEs and natural frequencies as the input parameters and damage states as output to train the ELM MODEl. Also, noise effect on the measured modal data has been investigated. The present method is applied to three examples consisting of a four span continuous beam, plane steel truss and four story plane frame. The obtained results demonstrated the accuracy and efficiency of the proposed method using incomplete modal data. Also, the results obtained indicate that the proposed method is a promising procedure for damage identification in spite of use of noisy modal data.

In this article, a non-destructive method for the frequency analysis and multi-crack detection in rotating shafts is presented, using transfer matrix method (TMM) and based on the Timoshenko beam theory. The cracks can be placed in different angles with respect to each other. The presence of cracks in structures change the local flexibility and results in reduction of natural frequency. The TMM is exerted for the frequency analysis of the shafts with discrepant boundary conditions. The resultant frequencies are used for requiring the MODE SHAPEs of the shaft corresponding to the two perpendicular planes (x-z and y-z). Subtracting these two MODE SHAPEs gives the position of the crack (cracks). Finally, the required frequencies by TMM are compared with some available experimental results. Close adaptation between these results is representing the high accuracy of the novel transfer matrix method.

SHAPE memory alloys (SMAs) are suitable candidates in various fields of engineering. One advantage of these alloys is their capabilities in developing high strain and force. In addition to these great features, lightweight and super-elastic behavior are other traits of these materials. These specifications are of such importance and allow SMAs to be suitably used in further engineering applications. However, their intrinsic hysteresis non-linear behavior makes their usage as position actuators difficult. Despite this challenge there are various methods proposed in the literature to MODEl the hysteresis behavior of such materials. In this paper, a generalized Prandtl-Ishlinskii MODEl, because of its simplicity, efficiency and inverse analytical capability, has been used for MODEling the SMA behavior. In addition, the hysteresis MODEling has been validated via experimental data of one of the articles. In the control section, however, two control systems consisting of PID and fuzzy sliding MODE controllers have been used. Fuzzy sliding MODE control system is a method that can be used in systems without mathematical MODEl and leads to increased robustness. It is shown in this paper that by using this method, it is possible to apply a suitable control input to the system in order to remove the error signal. However, by using PID controllers, the error signal is not acceptable due to the constant controller coefficients. The results illustrate a more efficient performance of fuzzy sliding MODE controller with respect to the classical PID controller.

Structural health monitoring and damage detection is one of the most important subjects for mechanic and aerospace engineers. Structural fault can cause uncompensated problems for both human and environment. There are several methods for solving this problem, but the most useful methods are those which focuse on structural change in the vibrational properties. This paper presents a feasibility study on locating damage in circular cylindrical fiber-reinforced composite shells based on MODE SHAPE methods and the sensibility of different damage intensity. In view of the fact that damage detections based on SHAPE MODE which do not use unprepared data are less reliable, in comparison by other damage detection methods, and highly efficient method mentioned depended on accuracy of modal testing and data extraction. As a whole, this paper shows that among the methods which used damage oriented approach, the first hole with thickness of 4mm in the other stages are more able to detect damage detection.

The use of structural vibration is one of the bridge health monitoring approaches which is often costly, time-consuming. The response of a passing vehicle includes the bridge response so that it is used for extracting the bridge modal parameters. In this paper, the transmissibility measurement of a passing vehicle is employed in order to identify the bridge MODE SHAPE indirectly. As the sensor is embedded on the axle of the vehicle, recording the signal is fulfilled during the vehicle passage and there is no need to stop the vehicle. On the other hand, there is white noise assumption in most other techniques, but excitation characteristics are not considered in the proposed method which is another advantage. In the numerical simulation, the bridge is assumed to be Euler Bernoulli and the vehicle is MODEled as a 4DOF system. Solving the vehicle-bridge interaction equations, the acceleration of all degrees of freedom are obtained. Afterwards, the MODE SHAPE is identified by applying the short time transmissibility measurement on the acceleration. Since the performance of the indirect methods in real cases is associated with many obstacles and challenges, a setup for experimental verification of the proposed method has been designed and constructed in a laboratory. Numerical simulations and experimental results indicate the capability of the proposed method for indirect identification of bridge MODE SHAPE.

Structures are subjected to a variety of environmental and loading conditions over time, and minor damage to structural elements may occur. By timely identifying damage and repairing damaged locations, it is possible to prevent the spread and development of damage to other elements and, as a result, the overall destruction of the structure. This article discusses the identification and determination of the location of damage in steel plates based on the use of the primary and secondary SHAPEs of vibration MODEs and the analytical method of two-dimensional wavelet analysis. MODElling and frequency analysis of the plate were performed in ABAQUS software, and the primary and secondary MODE SHAPEs were extracted. To determine the location of the damage, a damage detection index (DDI) was proposed based on the angle between the primary and secondary MODE SHAPE vectors and the diagonal detail coefficients obtained from the wavelet analysis of the primary and secondary MODE SHAPEs. The results showed that by using this index, damage can be identified by identifying peaks resulting from irregularities and disturbances. Also, the DDI value of the damage was dependent on the severity of damage occurring in a damaged situation, and the height of the disorder peaks increased with increased damage only at that damage position.

In giant magnetostrictive transducer, Young modulus of the core considerably alters with changing its magnetic level. Young modulus change in Terfenol-D core has the highest value. This effect changes the resonance frequency and MODE SHAPEs of the transducer. This subject in Terfenol-D resonance transducer is studied in this paper. For this purpose, a resonance Terfenol-D transducer has been designed and fabricated. Node locations in the transducer are considered to add pre-load and bias mechanisms. Effect of Young modulus change on resonance frequency and MODE SHAPE were studied both analytically and by ANSYS FEM software. Range of resonance frequency change in the first MODE is 1000 Hz and in the second MODE is 100 HZ. MODE SHAPEs changes are limited for both MODEs. In 40kA/m magnetic field bias, results from analytical and FEM simulation were verified with experimental results. Resonance frequency in this bias is 3100 Hz for the first MODE and 8252 Hz for the second MODE. Results have acceptable agreement with experimental results. Moreover, in this bias magnetic field, impedance responses between first and second MODEs are compared. Results show that selecting second MODE is preferable for reducing disturbance of Young Modulus change on vibrational behavior.