To retrofit or not to retrofit?

Under what conditions is it economically convenient to seismic retrofit a structure? This paper present a procedure whose results allow to give a simple answer to the above question, central in earthquake engineering and, in a broader context, in any man-made activity. The procedure uses, as a starting point, the results of a standard reliability analysis conducted on the structure in its present state and after retrofitting. Once these are known, expressed in terms of mean rate of exceedance of specified limit states, it is shown that it is possible to compute whether the upgrading should be made after all and how convenient it is. sumptions to make the problem tractable are clearly listed and appear, in the authors’s viewpoint, quite reasonable. The final results are presented both in diagrams and with a simple formula. The method is finally applied to two cases, already studied and presented by the authors, which had been developed up to the computations of the mean rate of failure: bridges on an Italian highway stretch (Donferri et al. Autostrade 1998;2:7-15) and a hospital in Tuscany (Ferrini et al. XII World Conference on Earthquake Engineering, Auckland, New Zealand, Paper No. 2102, 2000.).