Sensitivity based method for structural dynamic model improvement

Sensitivity analysis, the study of how a structure's dynamic characteristics change with design variables, has been used to predict structural modification effects in design for many decades. In this paper, methods for calculating the eigensensitivity, frequency response function sensitivity and its modified new formulation are presented. The implementation of these sensitivity analyses to the practice of finite element model improvement using vibration test data, which is one of the major applications of experimental modal testing, is discussed. Since it is very difficult in practice to measure all the coordinates which are specified in the finite element model, sensitivity based methods become essential and are, in fact, the only appropriate methods of tackling the problem of finite element model improvement. Comparisons of these methods are made in terms of the amount of measured data required, the speed of convergence and the magnitudes of modelling errors. Also, it is identified that the inverse iteration technique can be effectively used to minimize the computational costs involved. The finite element model of a plane truss structure is used in numerical case studies to demonstrate the effectiveness of the applications of these sensitivity based methods to practical engineering structures.