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.