Seismic vulnerability assessment of existing buildings

One of the main research areas of the Applied Computing and Mechanics laboratory (IMAC) at the École Polytechnique Fédérale de Lausanne (EPFL) is the seismic risk assessment of the existing building stock at an urban scale. Such analysis enables to forecast future earthquake impacts in terms of socio-economic losses. This forecast is then used to develop risk mitigation strategies and adapted emergency management solutions. It is with the same purpose that the Pontificia Universidad Católica de Chile (UC) works alongside the Research Center for Integrated Disaster Risk Management (CIGIDEN) on seismic risk assessment in Chile. One of the CIGIDEN’s flagship research lines is the vulnerability and risk assessment of physical and social systems — within which is included the study of integrated response with respect to human agents inhabiting structures and networks while being subject to direct and ensuing effects caused by earthquakes. It is within this larger project that the opportunity to study Santiago’s building stock arose. The aim of this thesis is to compare the seismic vulnerability assessment approaches of Chile and Switzerland by assessing Santiago’s building stock. Keeping this in mind, a second objective is to provide cartographic representations of the probabilities of damage degree due to seismic action on existing buildings for both methodologies. Such representations may be very useful in management of post-event emergency phases. The whole study could fit in the CIGIDEN global project to subsequently investigate the interactions between seismic impacts on buildings and crucial networks such as energy, health or transportation networks. This thesis starts by covering a state of the art of the seismic risk assessment methodologies in Chile and Switzerland. Here are also developed parameters that play a role in the assessment processes, such as seismic hazard, construction codes, exposure models, capacity and fragility models. A vulnerability assessment is achieved by applying both Chilean and Swiss approaches to Santiago’s building stock. To provide a tangible validation source of the computed results, assessments are performed using a scenario analysis based on the seismic hazard of the earthquake that occurred off the coast of central Chile on February 27th 2010. In doing so, theoretical results are compared with the official damage report released by the government. Cartographic representations of the degree of damage due to seismic action are then realised. The study ends with a comparison between the different approaches. The assumptions made and their influences on the results are reviewed, the different goals achieved during this project are listed and commented. Finally, perspectives for future work and ideas for further improvement of the assessment are discussed.