Una nuova definizione normativa del carico aerodinamico e del limite di stabilità al flutter per gli impalcati da ponte

This paper discusses the approach to the response of bridge decks under wind proposed in the new CNR-DT 207/2008 Guidelines, and it underlines its background and limits. In some cases bridge structures are very sensitive to wind loads and their behaviour can be extremely complex. Therefore this subject requires particular attention and the conclusions drawn herein have to be considered as a first step towards a codifiable definition of wind loads on bridge decks. In particular, the mean aerodynamic load and the limit of flutter stability are dealt with in the CNR Guidelines. The approach suggested is based on a rather large amount of experimental data, as well as on theoretical results. Concerning the mean aerodynamic load, the CNR Guidelines have three main targets with respect to Eurocode 1: the simplification of an approach which is considered in a few cases too complex for practical application, the elimination of some provisions which seem not to be confirmed by the experimental data and a correction of some numerical values which turned out to be on the unsafe side. A first approach to the analysis of twin decks is also suggested. Concerning flutter stability, in the CNR Guidelines an attempt is made to cover a field which is not dealt with by Eurocode 1, with the purpose of identifying possible critical cases for which more investigations are needed, possibly through wind-tunnel testing.