Finite Element method Elia Bon*, Antonella Frigerio*, Guido Mazzà* Scientific Bulletin TUCEB- Vol. 1 Marzo 2007 * CESI RICERCA The construction industry at European level is increasingly involved in the safety reassessment and rehabilitation of existing structures considering the limited available resources for new constructions, the greater environmental awareness and the cultural desire to maintain historic structures. Mathematical models of civil engineering structures are essential to conjugate structural safety, rehabilitations design and life extension. Given to the shortcomings in design data and surveys as a basis for structural models, it is clear that better non-destructive methods are useful in order to create more reliable numerical models. The HISTRIDE methodology, here presented, greatly extends and simplifies a non-destructive identification approach based on the modal structural response. The physical/mechanical parameters of the Finite Element model of a structure are modified to reduce the error between experimental modal features and computed ones. HISTRIDE is a software environment, running on a desktop PC, developed initially in the frame of the EC ESPRIT Programme. Recently, within the frame of the public research funding for the Italian Electric Sector (named "Ricerca di Sistema"), CESI RICERCA has recently improved the least squares algorithm of the HISTRIDE identification process in order to avoid divergent oscillations that move away from the structural response. The Coupled Local Minimizers (CLM) method has been implemented. This method is based on a cooperative search mechanism set up by performing simultaneously a number of local optimization runs, which are coupled together by information exchange instead of running independently. At first the HISTRIDE process will be presented with reference to a full scale validation test; afterwards a theoretical description of the Coupled Local Minimizers Method will follow.