Comparative non-structural vulnerability assessment methods for historical residential masonry buildings

The determination of seismic risk is the foundation for risk mitigation decision-making and a key step in risk management. Large corporations and other enterprises (e.g., local governments) analyze their 'portfolio' of properties, to determine how to best allocate limited funds for structural strengthening of buildings, or other risk reduction measures such as emergency planning. When assessing the seismic vulnerability of buildings, it is essential to first establish the project objectives, before subsequently choosing the most appropriate strategy and tools necessary for building assessment and fulfillment of these objectives. It is also extremely important to understand the difference between the detailed approaches used for individual building assessment and those methods most efficient for larger scale analysis, pursued for city center assessment. While the latter results can be used as a general measure of seismic risk for different types of buildings, the actual seismic risk for any individual building may vary considerably and will depend upon its exact configuration and condition. In this study, some historical masonry buildings located in Alsace France are considered and the dynamic characteristics of these structures were estimated by the analysis of seismic noise recordings by sensors installed at each floor of the buildings under study. The estimated dynamic properties for small amplitude vibrations of these historical structures were used to derive fragility curves through vulnerability models with different level of complexity and accuracy. These fragility curves have been calculated using incremental dynamic analysis for the seismic demands generally imposed upon linear and slightly nonlinear models of single and multiple degrees of freedom, which is the case for the effects of induced seismicity. Considering the latter case of induced seismicity, the vulnerability assessment requires the expected damage to refer to non-structural components. The conclusions through comparison of the results of this study in terms of refinement of the verified structural models will prove useful for both local end-users and industrial stakeholders, with a clear perspective for a better understanding of the risk related to induced and triggered seismicity and its sound management.