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In this paper, a new FRF-based model updating method is proposed based on the Structural Modification Using experimental frequency Response Functions (SMURF) method. The method deals with the complex Frequency Response Functions (FRFs) and aims to update the lumped parameters of system. The parameters of FE model are updated accurately using only a limited data. A twelve Degrees Of Freedom system is considered as a test case in a simulated experiment. The convergence of the method and the accuracy with which it corrects the FE model are studied. Moreover, the effects of the number of modes, the frequency range of interest, the coordinate incompleteness and noise on the quality of the updated model are investigated. Finally a cantilever beam was used as experimental case study. The results show that the updated FRFs are in good agreement with their experimental counterparts.

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Hydraulic engine mounts isolate the structure of the vehicle from powertrain vibrations and also prevent excess motions of the powertrain due to shock excitations. In this paper, dynamic stiffness of a hydraulic engine mount in low frequency range (shock frequency range) is predicted using modal test data and three-dimensional finite element model through an iterative model updating procedure. The implemented model encompasses elastomeric material’s nonlinearity, fluid-structure-interaction and internal resonances of mount. Mesh morphing technique is used to model the fluid-structure-interaction. The results showed that the introduced procedure can successfully predict the shock isolation behaviour of the hydraulic engine mount.

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In this paper, a new model called connective layer is developed for simulation of linear dynamical behavior of bolted lap joints and model updating in 3D models. Connective layer unifies neighboring zones on sides of common surfaces of substructures in joint region. The constitutive relation of connective elements is defined by decomposing it into its normal and shear components. Unknown and different elastic properties with respect to the neighboring solid elements are defined for connective layer and the unknown parameters of the model are identified by a finite element model updating technique using modal test data. The frequency response of the structure is measured by exciting the structure using an impact hammer. Using an optimization algorithm in ANSYS, the difference between the experimentally measured frequencies and the predictions of the parametric model is minimized as objective function. The connective element performance is demonstrated by application to an actual structure containing a single lap bolted joint coupling two identical aluminum alloy 7075-T651 beams and finally comparison of results to those of interface elements. The outcomes of presented model have good correlation with experimental results. The proposed method predicts the higher mode frequencies which don’t have participation in model updating process with minimum error in comparison to those of interface element. Due to simplicity, accurate and computationally efficient manner, this model can be incorporated into commercial finite element codes to simulate bolted joints in large and complex structures.

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In this paper, experimental data have been used to develop a semi empirical relationship for double-ellipsoidal heat source to model the welding process of a T-shape fillet weld of carbon steel AISI 1020 and stainless steel 304. This model is used in a finite element based computer code to simulate the three dimensional welding process and obtain the temperature profile around the weldment. Experimental data in the form of temperature for certain points have been recorded during the welding process using a computerized data processing system which has been designed for this purpose. Also, the thickness of the weldment layers has been compared by observing their hardness and crystallography. By comparing experimental data with numerical result, the coefficient of the model has been determined using “model updating” process. The effects of material properties and welding parameters have been studied to insure the generality of the model. This model can be used to evaluate the quality of the welding and thickness of the heat affected zone as well as the risks during the welding process such as burn-through and hot cracking. The main advantage of this model is that the number of coefficients is reduced to only one parameter and the rest have been related to the physical and geometrical characteristics of the weld. Results of the numerical simulation obtained using this model show that the major factors which affect the temperature distribution around the weldment are material conductivity, plate thickness, input heating and welding speed.

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In transmission lines the environmental disturbances causes vibration of the lines (cables) as well as the structure which have destructive effect on the line and its components. To overcome this harmful effect, it seems necessary to reduce the transmission line vibration level. One of the most frequent methods for reducing the transverse vibration of cables is using dynamical dampers such as Stockbridge damper. Complication of calculating the bending stiffness as well as the energy absorption mechanism of these dampers makes it more difficult to be modeled. In this study the dynamical characteristics of Stockbridge damper considering the damping effect are studied. For system identification of Stockbridge damper, it is modeled as a 4DOF system and its various unknown parameters are obtained using model updating method and experimental modal analysis (EMA) which is optimized by Artificial Intelligence (AI) method. Then the effects of varying these parameters on its energy absorption are discussed. Finally, to validate the analytical results, some experimental tests were carried out on the energy absorption of Stockbridge damper. The analytical results are in good agreement with the experiments.

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The detection of changes in the dynamic behavior of structures is an important issue in structural safety assessment. Deployment and servicing of marine and coastal structures such as piers in the marine environment with constantly changing, requires understanding the dynamic behavior of these structures to prevent possible damage. Among the factors of uncertainty in understanding the dynamic performance of piers is uncertainties related to semi-rigid connection of deck to piles. According to this fact that the main mass of the structure is on deck, the connection of deck to piles is very important. In this study, experimental and numerical model of beach piers were studied. A Test on experimental modal analysis was performed to determine the response of structures. A numerical model of the structure prepared and theory of modal analysis was performed on it. Then, based on the finite element model updating of structure approach, identify and determine the percentages of semi-rigid connections. Results show this fact the connection isn’t fully rigid. According to the present method can be compared to determine the percentage of semi-rigid connections and prepare the finite element model with more adaptable to the experimental model. Updated results with this method were very close to the real model.

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The present article deals with analytical modeling of boring bar dynamics as well as identification of unknown parameters for the dynamic model. Experimental modal analysis is utilized to measure the Frequency Response Functions (FRFs) of cutting tool. Using the analytical methods of modal analysis theory, dynamic parameters of boring bar (i.e. natural frequencies, damping ratios and modeshapes) are extracted from curve fitting of experimental FRFs. A new physical configuration is proposed, in order to accurately estimate the dynamic response of boring bar in time/frequency domains. In the proposed dynamic model, boring bar is modeled as an Euler-Bernoulli beam with flexible support and tip mass. The mechanical properties (i.e. modulus of elasticity and density) are considered to be constant along beam length. The flexibility of boring bar's clamping interface is modeled by linear translational/torsional spring elements. Particle Swarm Optimization (PSO) is utilized to identify the unknown parameters of dynamic model. The parameters include translational/rotational clamping stiffness and dimensionless correction factors for boring bar's diameter/tip mass. These parameters directly control the mass/stiffness distribution of proposed dynamic model. The FRFs obtained from updated model of boring bar are compared with experimental FRFs. It is shown that, by optimal selection of unknown parameters, boring bar FRFs can be accurately calculated at any point along its length. Hence, by incorporating the dynamic model of passive/active actuator into the proposed dynamic model, the stability lobes of dampened boring bars can be predicted.

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The precise finite element model is an efficient tool for vibrational analysis. It should be mentioned that, in structural dynamic analysis finite element models of system should be able to accurately predict system characteristics such as natural frequencies. Contrary to static analysis, in structural dynamic analysis, it is not possible to overestimate system characteristics or apply safety factor for predicted characteristics; that means that the exact values of system characteristics such as natural frequencies, should be derived in structural dynamic. According to this, constructing a reliable model in the structure dynamic always has great degree of importance in vibrational analysis. In this study, it has been tried to extract a reliable finite element model for a row of a sample turbine of RollsRoyce brand using empirical results. So, the material properties of the disk and the connection between the disk and the blade are corrected and updated using experimental modal analysis results. Also, it has been tried to propose new method to model and update the disk and blade joint. Finally, reliable finite element model could be used for more analysis such as derivation of Campbell diagrams of system.

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In this paper, a new method for determining the Young's modulus of structural elements, using the finite element model updating approach, is presented. The model updating is the correction of the numerical model of a structure based on measured data from the real structure. Therefore, after introducing a case study of an aluminum alloy (7075-T651) beam, the frequency of bending vibrations of the case study was measured, using frequency response functions derived from the modal test. Then, Young's modulus for the case study was calculated, using the relationships in the ASTM E 1876-01standard and also the analytical relations governing Euler–Bernoulli beam behavior. The results of the model updating method indicate that there is a very good adaptation with the results of the two recent approaches, the Standard and Euler–Bernoulli beam relations. As a result, this method can be developed with good precision to identify the Young’s modulus in structural elements with more complex shapes, where the relations derived from the aforementioned standard and analytical relations are not efficient due to geometric constraints.

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The safety of bridges as the vital arteries of cities is of great importance. There are several factors that raise concerns about the safe performance of bridges, and resolving these concerns are dependent on the appropriate decision-making of urban managers throughout the service life of bridge. These factors can be divided into two major types. The first type are factors affecting the safety of a part or whole structure of bridge and producing concerns about the bridge collapse. For easing the danger of collapse, totally or partially, a proper decision should be made to improve the behavior of a specific part of bridge at a certain time during its service life. The second type are factors influencing the safety of one or more bridge elements and increasing the life cycle costs of bridge. To prevent the growth of bridge costs due to deterioration, an appropriate plan for repair and maintenance should be implemented in order to enhance the condition of one or several elements.
 In order to make the right decision, it is necessary to obtain accurate information on the condition of bridges. One of the best ways to get this information is to use bridge health monitoring. Health monitoring is the process of information acquisition from structure by installing sensors on its components and analyzing the data obtained from implemented sensors. By bridge structural health monitoring and interpreting the gathered data, the access to accurate and timely information, which is consistent with the reality of the bridge structure, is provided. Having the correct information about the bridge, the managers can decide at a lower level of risk. However, choosing specific monitoring strategy among different health monitoring systems for a bridge is a challenge that should be solved. A Quantitative index is needed to find the best technically and economically monitoring system.
 The value of information (VoI) analysis is used for determining the effectiveness of monitoring information in decision-making. VoI is a method which quantifies the price of information and specifies the cost-effectiveness of decisions made on the basis of monitoring. This analysis also makes it possible to choose the most economical monitoring strategy among several alternatives. In the VoI calculation, all the uncertainties involved in the performance of a Health monitoring and probabilities of any anticipated event are considered. Thus, the decision making based on VoI is risk-based and reliable especially for important structures like bridges.
In this paper, after investigating the worries and solutions for eliminating worries about the bridges in detail and introducing the applications of structural health monitoring (SHM) systems for bridges, the equations governing the VoI analysis is presented and the procedures for determining the VoI is discussed, and as an example, the VoI analysis of a bridge is discussed. According to the results of this analysis, implementing a specific amount of strain gauges with specific accuracy can provide worthy information about the bridge safety for the manager. Moreover, by the VoI analysis, the best approach for sensing system of SHM in the bridge is determined.