Statistical Analysis of Modal Parameters Using the Bootstrap

Structural dynamic testing is concerned with the estimation of system properties, including frequency response functions and modal characteristics. These properties are derived from tests on the structure of interest, during which excitations and responses are measured and Fourier techniques are used to reduce the data zhe inputs used in a test are frequently random, and they excite random responses h the structure of interest. when these random inputs and responses are analyzed they yiekj estimates of system properties that are random variabk and random process reaikations. Of course, such estimates of system properties vary randomly from one test to another, but even when deterministic inputs are used to excite a structure, the estimated properties vary f m test to test. when test excitations and responses are normally distributed, classical techniques permit us to Statistically analyze ihputs, responses, and some system parametem However, when the input excitations are non-normal, the system is nonlinear, and/or the property of interest is anything but the simplest# the classical analyses break abwn. The bootstrap is a technique for the statistical analysis of data that are not necessarily normaliy distributed. It can be used to statistically analyze any measure of input excitation or response, or any system pmperty, when data are available to make an estimate. It is designed to estimate the standard error, bias, and confidence intervals of parameter estimates. This paper shows how the bootstrap can be applied to the statiskal analysis of modal parameters.