The use of changes in dynamic system characteristics to detect damage has received considerable attention during the last years. Within this context, FE model updating technique, which belongs to the class of inverse problems in classical mechanics, is used to detect, locate and quantify damage. In this study, a sensitivity-based finite element (FE) model updating scheme using a trust region algorithm is developed and implemented in a complex structure. A damage scenario is applied on the structure in which the stiffness values of the beam elements close to the beam–column joints are decreased by stiffness reduction factors. A worst case and complex damage pattern is assumed such that the stiffnesses of adjacent elements are decreased by substantially different stiffness reduction factors. The objective of the model updating is to minimize the differences between the eigenfrequency and eigenmodes residuals. The updating parameters of the structure are the stiffness reduction factors. The changes of these parameters are determined iteratively by solving a nonlinear constrained optimization problem. The FE model updating algorithm is also tested in the presence of two levels of noise in simulated measurements. In all three cases, the updated MAC values are above 99% and the relative eigenfrequency differences improve substantially after model updating. In cases without noise and with moderate levels of noise; detection, localization and quantification of damage are successfully accomplished. In the case with substantially noisy measurements, detection and localization of damage are successfully realized. Damage quantification is also promising in the presence of high noise as the algorithm can still predict 18 out of 24 damage parameters relatively accurately in that case.
No abstract is provided for this article.
In the last two decades, many studies have reported the effectiveness of Experimental Modal Analysis and Finite Element Model Updating in mechanical and aerospace engineering, where they represent useful tools for Structural Health recognition and can provide an information base for detection, assessment and quantification of structural damage due to exercise actions and exceptional events. The applications of Damage Detection techniques to civil constructions left some still not well clarified points, due to the great variety of structural typologies, material properties, boundary conditions and possible damage patterns, as in the case of seismic damage. In order to design post-earthquake rehabilitation interventions, in fact a careful knowledge of the damage distribution and residual structural capacity is obviously needed and this can be very expensive and time consuming. However, the application of vibration based damage identification techniques to high ductile structures designed according to seismic capacity approach can improve the feasibility, reliability and efficiency of these methods. In the present study, Finite Element Model Updating procedures based on vibration measurements were used to detect, assess and quantify the structural damage of a high ductile steel–concrete composite frame subjected to increasing seismic damage by means of pseudo dynamic and cyclic test at the Joint Research Centre (Ispra, Italy). The updating process, repeated for three damage levels, has been applied to different finite element structural models (addressing different modelling strategies), allowing a comprehensive description and quantification of the progressive degradation of beam-to-column joints, devoted to dissipate the seismic energy by design.
No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
Single and double panels are commonly employed in noise control, e.g., as partitioning elements between rooms and to enclose noisy machines. In presence of narrowband disturbances, related for example to rotating machines, further improvements in sound insulation can be obtained by properly distributing the material within the area of the panels. This allows maximizing the sound Transmission Loss (TL) in the frequency band of interest by controlling structural resonances and antiresonances. In order to achieve this goal, in this work, we apply numerical topology optimization to find the optimal material thickness distribution for single and double panels. In the iterative design process, single panels are schematized through a simple mechanical Finite Element (FE) model, while double panels are modelled considering the vibroacoustic coupling between the two mechanical plates and the internal acoustic air cavity. The sound insulation properties of the designed solution are evaluated by TL computations through hybrid Finite Element-Statistical Energy Analysis (FE-SEA) simulations. The method is applied targeting different frequency bands in the audible range and focusing on practically relevant design cases, such as single and double PMMA and glazing panels.
Predicting the sound insulation between two rooms is a complex problem since not only the direct path through the separating element but also the flanking transmission paths can largely influence the sound insulation of the system. An important parameter for calculating flanking transmission is the vibration reduction index, which relates to the transmission coefficient between the connected plates. The international building acoustics standard ISO 12354-1/2 provides prediction formulas for the vibration reduction index of single wall junctions, but not for double wall junctions. A new hybrid-deterministic approach is proposed to calculate flanking transmission across double wall junctions. The walls and floors are modelled as diffuse subsystems while the connection between the double wall is modelled deterministically. This approach relies on the diffuse field reciprocity relationship, which relates the vibration transmission to the direct field dynamic stiffness of the subsystems (walls and floors), i.e., the dynamic stiffness of the equivalent infinite subsystem as observed at the junction. In contrast to existing approaches, the finite size of the junction is properly taken into account in this way. The new approach is applied to different types of double wall junctions to determine simplified regression formulas for practical sound insulation design.
