|M.Sc Student||Alexander Chanan|
|Subject||Fragility Curves Assessment of Seismic Loads as a|
Potential Cause of Structural Failure on an
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Oded Rabinovitch|
|Full Thesis text - in Hebrew|
The study aims to face the challenges related to the estimation of the potential structural damage caused by seismic activity in an archaeological site, as well as revealing quantitative data about the seismic activity of the site based on the assessment of the structural findings. Such information is critically important for the seismic design of new buildings and for the retrofitting of existing ones. To achieve that goal, analytical, numerical, and probabilistic tools are developed and combined, with focus on archaeological findings of manmade structures that were damaged by pre-instrumental paleo-earthquakes. The goal is to develop a methodology for the evaluation of the seismic vulnerability of such structures, to assess their response to past seismic activity, and to gather and update information for future seismic design.
In the first stage, an analytic-probabilistic procedure for the evaluation of the seismic vulnerability of masonry structures was developed. The procedure adopts the concept of fragility curves and integrates structural analysis tools into a Monte-Carlo type of probabilistic analysis. For the former, a structural model based on Discontinuous Deformation Analysis principles was formulated. The model of a 2D masonry wall was used to perform two types of analyses, Pushover Analysis and Response History Analysis.
In the second stage, an approach for converting archaeological findings that can be attributed to past earthquakes into data that is relevant to the probability of future seismic activity is developed. The main methodology adopted in this phase combines the concept of fragility curves generated in the first stage with the concept of Bayes theorem applied to the seismic Hazard Curves (HC). The derived methodology uses the gathered archaeo-seismological data to update the latter by means of Bayes theorem. Specifically, if it is known that the cause of failure in a masonry structure is a past earthquake, it is possible to conceptually “invert” the fragility curve: instead of evaluating the probability of damage for a given seismic load, evaluating the probability of a seismic load given the level of structural damage or structural collapse in a seismic event. Then, the seismic HC is updated using the fragility curve and the notion that the damage did occur in a seismic event using Bayes theorem.
The procedure of updating the seismic HC of the specific site using Bayes theorem becomes significant when it is reported or observed that a highly resistance structure has failed under seismic load, as an indicator of a past major earthquake in the archaeological site region. Such information can potentially improve on the seismic hazard evaluation and consequently, the structural design load. A simulative case study of an existing low resistance structure which didn’t fail under any seismic load in the given exposure period can point that mid to strong seismic event didn't strike in the archaeological site region. This issue, as well as using different modelling approaches and applying the concepts and procedure developed in this study to well-documented archaeological sites define new directions for future research.