STRUCTURAL PARAMETER UPDATING USING A MASS ADDITION AND/OR STIFFNESS REDUCTION

摘要

Most dynamic structural systems are subject to an increase of mass and/or stiffness reduction from failures in the elastic elements such as columns. These changes of the design parameters represent a perturbations of such structure. It is very important to adjust or update dynamic structural models subject to those conditions. A single column model as a simple structure attached with different lumped mass were bolted rigidly to the column to be of two, three and four masses at equal spaces along the vertical column high. Four steel columns of 55 cm long 1×1 cm cross section were used, three of them were notched to a depth of 1, 2 and 5 mm at 40 cm, using electrodis-charge wire cutting machine. Experimentally all models eigen-frequencies and damping factors were obtained using Dual Signal Analyzer from 0 to 400 Hz. An analytical model was built and analyzed using personal computer to obtain eigenpairs of different models "original and perturbed". The design parameters and eigenfrequencies were used to update the system design variables. The results shows that the perturbing method changes the dynamic behaviour and characteristics of the system which can be theoretically predicted.