SENSITIVITY BASED METHOD FOR STRUCTURAL DYNAMIC-MODEL IMPROVEMENT

Sensitivity analysis, the study of how a structure's dynamic character istics change with design variables, has been used to predict structur al modification effects in design for many decades. In this paper, met hods for calculating the eigensensitivity, frequency response function sensitivity and its modified new formulation are presented. The imple mentation of these sensitivity analyses to the practice of finite elem ent model improvement using vibration test data, which is one of the m ajor applications of experimental modal testing, is discussed. Since i t is very difficult in practice to measure all the coordinates which a re specified in the finite element model, sensitivity based methods be come essential and are, in fact, the only appropriate methods of tackl ing the problem of finite element model improvement. Comparisons of th ese 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 effecti vely used to minimize the computational costs involved. The finite ele ment model of a plane truss structure is used in numerical case studie s to demonstrate the effectiveness of the applications of these sensit ivity based methods to practical engineering structures.