Papers by Keyword: Damage Indices

Abstract: Lamb waves (LW) are used for damage detection and health monitoring due to the long range propagation ability and sensitivity to structural integrity changes as well as their robustness in different applications. However, due to the dispersive character and multimode nature of LWs, analysis of the acquired ultrasonic signals is very complex. It becomes even more difficult when applied to a complex structure, for instance, an aircraft component with riveted joints and stringers characterized by difficult geometries. Therefore, numerous approaches to the evaluation of damage indices have been proposed in the literature. In this paper, comparison a number of damage indices applied to LWs testing in aircraft aluminum panels. The damage indices, known from the literature have been selected from the application point of view. Artificial neural network has been used for the classification of fatigue cracks and artificial damages induced in the specimens taken from a real aircraft structure. Article presents results of simulation, data analysis and data classification obtained using selected and dedicated neural network. The main aim of the presented research was to develop signal processing and signal classification methods for an aircraft health monitoring system. The article presents a part of the research carried out in the project named SYMOST.

Abstract: During the past earthquakes, different low ductile failure modes are observed in the gravity design structures and thus, the most of existing damage indices may fail to assess the damage of gravity design structures accurately in referring to the two main performance levels: immediate occupancy and ultimate limit state. Therefore, this study investigates the possible damage indices for the damage assessment of gravity design frames. For this purpose, among the existing damage indices in the literature, this study considers the inter-story drift and the natural period based damage indices. In addition, two new damage indices based on the wavelet based energy and the dominant inelastic period of a building are also considered in this study. Furthermore, the damage assessment results from the four damage indices for three gravity design buildings are compared and discussed. From the comparison, linear correlations between the inter-storey drift based damage index and the wavelet energy based index, and dominant inelastic period based damage index are observed. Finally, this study concludes based on the observations that no significant effects of number of inelastic cycles to the damage assessment results for low ductile structures. However, this study also highlights the effects of number of inelastic cycles to the damage for medium and high ductile structures.

Abstract: Reinforced concrete (RC) structural walls are one of the most commonly used lateral load resisting systems for high-rise buildings in strong seismic regions because of its good lateral resistance. Serious damage occurs when RC structure subjected to strong seismic action. Classified and brief comment of documents concerning damage indices and its calculation methods are conducted. It could be concluded that most of the damage evaluative models can not directly consider the effect of cumulative damage of material to mechanical properties of structure. Suggestions are proposed to improve the accuracy in damage evaluation of RC structure.

Abstract: Deteriorated concrete structures are repaired by means of grouting. In order to evaluate the repair effectiveness two NDT techniques namely seismic tomography and acoustic emission are applied. Using traveling time of elastic waves, structural velocity is estimated. AE activity is monitored along with water pressurization of the permeability test. As a result, contrary to the common expectation that the velocity increase after filling with grouting agent, enormous amount of velocity drop was obtained after repair due to the incomplete developing process of grout material, whereas AE activity showed dramatic decrease after repair. Furthermore after comparison of those results to the quantity of grouting material, it became clear that damage indices based on AE activity exhibited well the actual damage of concrete structures.