Nondestructive Level III Damage Evaluation and System Identification in Structures Based on the Rate of the Total Energy

Abstract

Nondestructive damage detection methods provide beneficiary bases for planning an economical maintenance program for structures. Economically, detecting and repairing structural damages in their initial stage is desirable, and moreover it may prevent occurrences of disastrous losses especially in areas susceptible to hazardous loads such as earthquakes. Therefore, development of a general damage detection method that alarms degradations of structural properties is of interest.

In this dissertation, a level III non-destructive damage evaluation method, called DITER, is developed based on tracking the rate of the mechanical energy of a structural system. The objective is to simultaneously detect and size variations in the element-wise mass, stiffness, and damping characteristics of a structure, utilizing dynamic response data of the system. The effect of the proportional and non-proportional types of the inherent damping of the structure in the form of viscous resistance to strain of the material and Rayleigh damping, as well as the effect of passive seismic protective devices are considered in the method. Moreover, an iterative algorithm is proposed for the cases with missing load data

A sub-system approach is developed to make DITER applicable to a specific part of a structure. The advantages of this approach are limiting the excitations to the interested area only, and making DITER an appropriate option for structures with seismic protective systems.

While the method is applicable to a general structure, in this dissertation, it is explicitly developed for shear building models as well as for two-dimensional beams and frames. To address the geometrical non-linearity, an extended version of DITER is developed employing von Kármán nonlinearity. Several numerical verifications are presented to study the DITER performance under different types of supports, loadings, and damping characteristics as well as to consider the effects of the type, intensity, and geometry of the imposed damages. In addition, dynamic properties of a three-story office building are used to experimentally verify the DITER ability in detecting deteriorations in the structural stiffness.