Determination of storey stiffness of three-dimensional frame buildings

Abstract

Few past system identification studies have attempted structural models with many degrees-of-freedom (DOFs) owing to the numerical difficulty with regard to convergence and computational speed. Even fewer studies have considered a three-dimensional building with the torsional response taken into consideration. In this respect, an 'improved condensation' method for the system identification of multistorey three-dimensional frame buildings is developed. Specifically, reductions in storey stiffnesses are determined for the quantification of structural damage or deterioration in each storey of a building. Both static and kinematic condensations are employed to reduce the DOFs of a (complete) mathematical model for the building, resulting in a condensed model of much fewer DOFs. The modelling error is minimized by introducing a remedial model whose parameters are identified by using the extended Kalman filtering technique. A stiffness correction factor is computed to successively update the complete model. Finally the method yields integrity indices to quantify changes in the respective storey stiffnesses. A numerical simulation example of an asymmetric three-storey frame building which has a total of 270 DOFs is presented. Three cases of different damage status of the building are considered. The proposed method is implemented to identify the storey damages, under the influence of input and output noise. The numerical results show that this method accurately reports the extent of stiffness reduction at each storey of the building and is computationally efficient because of a smaller system used for identification in the remedial model. © 1995.