THE BUILDING CODE SIA 269/8 FOR A RISK-BASED SEISMIC SAFETY ASSESSMENT AND RETROFIT OF STRUCTURES IN SWITZERLAND

This contribution presents the central concepts of the swiss building code SIA 269/8 [1] for the verification of the seismic safety of existing structures. The first central concept of SIA 269/8 is the compliance factor. It indicates the degree of compliance of an existing structure in comparison with the requirements for new structures. The second central concept is the recommendation of measures based on the value of the compliance factor. If the seismic safety of an existing structure lies below a minimum threshold value of the compliance factor, retrofitting is mandatory to reach this minimum threshold whatever the costs. If the compliance factor is smaller than 1.0 and higher or equal to the minimum compliance factor, only efficient measures, with a risk reduction greater than the costs, have to be implemented. The third central concept of SIA 269/8 is the evaluation of the commensurability of measures through the explicit computation of their efficiency. The risk reduction is computed using a set of standardized curves linking the compliance factor with different risk unit values. The efficiency is computed as the ratio between the risk reduction in Swiss francs (CHF) per year and the annualized cost of measures. For the computation of the risk reduction for human life, a value of statistical life of 10 million Swiss francs is used. This elegant and relatively simple framework allows to focus retrofit measures for constructions with an unacceptable risk level as well as for constructions for which commensurate retrofit measures can be found. It has been widely applied in Switzerland since 2004 and is well accepted in practice.