Study on sensitivity of modal parameters for suspension bridges

Safety monitoring systems of structures generally resort to detecting possi ble changes of dynamic system parameters. Sensitivity analysis of these dyn amic system parameters may implement these techniques. Conventional structu ral eigenvalue problems are discussed in the scope of those systems with de terministic parameters. Large and flexible structures, such as suspension b ridges, actually possess stochastic material properties and these random pr operties unavoidably affect the dynamic system parameters. The sensitivity matrix of structural modal parameters to basic design variables has been es tablished in this paper. Moreover, second order statistics of natural frequ encies due to the randomness of material properties have been discussed. It is concluded from numerical analysis of a modem suspension bridge that alt hough the second order statistics of frequencies are small relatively to th e change of basic design variables, such as density of mass and modulus of elasticity, the sensitivities of modal parameters to these variables at dif ferent locations change in magnitude.