Final Activity Report Summary - PBSDOS (Performance based seismic design of structures) The objective of the project PBSDOS was to develop and validate an integrated methodology for the performance based seismic design and evaluation of structures, which explicitly accounted for multiple performance objectives with respective acceptable design spectra, based on rates of exceedance of performance levels and, eventually, on risks or target reliabilities. The research emphasis was on reinforced concrete buildings and highway bridges, focussing particularly on three-dimensional asymmetric buildings and bridges subjected to bi-directional earthquake action. To achieve this objective there were a number of tasks that needed to be carried out including: 1. investigation and systematic consideration of uncertainties, random and epistemic, that were relevant to this problem, e.g. those present in the evaluation of seismic hazard and the approximation involved in simplified non-linear methods of analysis used to predict the response, seismic damage and performance of structures; 2. improvement, validation, calibration and generalisation of the preliminary version of a performance based seismic design procedure previously suggested by the grant holder, which was essential for the application of the performance based seismic design methodology to three-dimensional structures subjected to multi-directional shaking; and 3. practical implementation of the resulting methodology placing special emphasis on the reduction of uncertainties attributed to the design methodology and the development of procedures and computational design tools whose use had to be straight ward in order to be easily utilised and appreciated by the profession. The method was developed by taking advantage of the experimental results obtained at the European laboratory for structural assessment, for irregular buildings and irregular bridges in particular, in close collaboration with the staff and the members of the research network 'LessLoss'.