Evaluación de vibraciones en el diagnóstico de estructurasEstudio de comportamiento de estructuras en deterioro

Résumé

The dynamic response of a structure throughout its service life varies due to deterioration caused by different factors, with environmental agents and loads being the main causes of degradation. Dynamic actions represent one of the major causes of damage, evidenced in fatigue phenomena, microcracking, cracking, plastic deformation, detachment and even collapse. This damage can usually be minimal for service loads and severe in the case of extraordinary high dynamic loads (impacts, earthquakes, explosions, strong winds). Interaction between the actions and the response can also cause significant damage as in the case of moderate service loads with response amplification due to resonance phenomena. In practice, the evaluation of structure condition is based mainly on visual observations and described by subjective indices that do not facilitate an accurate diagnosis of behavior, serviceability and safety. A reliable evaluation of the dynamic behavior of a structure depends on quantitative information rather than qualitative information, therefore, there is currently a need to develop diagnostic methodologies that include damage quantification parameters based on direct tests of vibrational response. In infrastructure management, there is a need for a more objective and reliable process for evaluating and quantifying the state of deterioration of structures to be used in routine inspections, aimed at control, maintenance and rehabilitation. This thesis studies the experimental evaluation methodologies of the vibrational response applied to the diagnosis of deteriorating structures. It focuses on finding standardized diagnostic practices that confidently determine the degree of compliance, deterioration or severity of damage in a structure, both for extreme load cases and normal operating conditions. The fundamental contributions start from the experimental study of the degradation of the properties of a structural laboratory model subjected to dynamic forces. The thesis is developed extensively with the execution of two deep experimental studies of real structures with a notorious degree of deterioration. Direct diagnosis techniques using damage inspection are compared to vibration-based techniques. Different ways of quantifying damage, deterioration, quality and discomfort were proposed. The development of this work begins by synthesising the bases and applications of the prediction, measurement and analysis of vibrations in structures, focused on generating diagnostic tools to implement in routine evaluation tests for service and safety conditions. In this sense, practical examples are shown that better illustrate the concepts involved. Tools for the identification of dynamic properties and damage quantification based on vibration tests are described.