Resumen de Daño sísmico y propiedades modales en estructuras de edificación
Rodrigo Esteban Alva Bañuelos
The time required to inspect damaged structures after an earthquake has a direct impact on the social and economic consequences of the event, which can be catastrophic. Developing tools to aid the inspection task is of great interest to reduce the impacts of seismic events and increase the resilience of cities. In this work we study the basis of a methodology for structural damage diagnosis, which contributes to make faster and more objective decisions about the safety and reoccupation of buildings after an earthquake. It is proposed to estimate the damage in buildings from the change in their dynamic properties. This concept is well established, but its use lacks an explicit and practical purpose of damage assessment. In this regard, we explore new remote sensing techniques for operational modal analysis. In the first part of this thesis, we study feasibility of estimating modal properties in different building types by means of an innovative remote sensing technique, based on Real Aperture Radar (RAR). To improve the quality of the measurements, novel signal analysis and data fusion techniques are explored. The results are contrasted with those obtained from conventional in-contact sensing techniques. The second part of the thesis focuses on the evaluation of structural damage and its relationship with the modal properties of the structure. Specifically, the increase of the fundamental period induced by stiffness degradation due to structural damage, is investigated. Finally, the main advantages and disadvantages of the different measurement techniques are discussed, as well as the increase of the structural period as a damage indicator. A relevant conclusion is that RAR technology can become a very useful tool after an earthquake. This technique allows the identification of modal parameters, not only of tall and flexible structures, but also of low- to medium-rise buildings, without the need to access the structure. Therefore, the time and cost of evaluations can be reduced, in addition to removing the risk of entering a damaged structure. It is worth mentioning that these tools would not only be useful in the post-earthquake emergency phase, where speed of assessment is critical, but also in the subsequent stages of damage assessment and for other purposes, such as structural health monitoring and numerical model calibration.
