Structural damage identification based on change in geometric modal strain energy–eigenvalue ratio

Abstract

This study presents a new damage identification method to locate and quantify damage using measured mode shapes and natural frequencies. A new vibration parameter, ratio of geometric modal strain energy to eigenvalue (GMSEE), has been developed and its change due to stiffness reduction has been formulated using a sensitivity matrix. This sensitivity matrix is estimated with measured modal parameters and basic information of the structure. For damage identification, firstly, the locations of damage and the correlative damage extents are identified by maximizing the correlation level between an analytical GMSEE change vector and a measured one. Herein, the genetic algorithm, which is a powerful evolutionary optimization algorithm, is utilized to solve this optimization problem. Secondly, the size of damage can be estimated using the proposed GMSEE technique and compared with a conventional technique using frequency change. A numerical 2D Truss bridge is used to demonstrate the performance of the proposed method in identifying single and multiple damage cases. Also, practicality of the method is tested with a laboratory eight degree-of-freedom system and a real bridge. Results illustrate the high capability of the method to identify structural damage with less modeling efforts.

Recent progress and future trends on damage identification methods for bridge structures

“…Shadan et al proposed a damage identification method using natural frequencies and frequency response functions data; the method was examined numerically through a reference example truss, and results show that the location and severity of damage were identified precisely in all cases. Nguyen et al developed a new vibration parameter, that is, ratio of geometric modal strain energy to eigenvalue, and a new damage identification method was proposed based on the parameter; the proposed method can identify the location and size of damage, and the performance and practicality of the method are verified through a numerical truss bridge. Seyedpoor and Montazer proposed a damage identification method for truss structures based on the flexibility‐based damage probability index and differential evolution algorithm; the problem of damage identification is transformed into an optimization problem and then the algorithm is employed to identify the actual location and severity of the damage; high efficiency of the two‐stage method for the truss structure is verified through numerical results of multiple damage cases.…”

Damage identification in a complex truss structure using modal characteristics correlation method and sensitivity-weighted search space

“…In order to estimate the change in elemental MSEE due to stiffness change, it is still assumed that the change in fractional modal strain energy is neglected. Based on the sensitivity analysis of elemental GMSEE, 11 the change in elemental MSEE can be estimated as follows…”

“…Based on change in vibration characteristics, many damage identification methods have been developed and many of them have shown their capability to cope with levels 2 and 3 of the damage identification problem. [3][4][5][6][7][8][9][10][11] However, these methods have mostly been validated with numerical models or simple experimental structures. Only few studies have been conducted for complex structures.…”

Finding Damage Localizations of a Planar Truss Using Modal Strain Energy Change

“…It is assumed that mode shapes have been identified and normalized by the mass matrix for both intact and damaged structures. In order to consider the effect of identification uncertainties, polluted mode shapes of the damaged structure are given by [16].…”

“…Liu et al [14] proposed a method to detect structural damages of offshore platforms by introducing the concept of grouping modal strain energy, which divided the elemental modal strain energy into axial tension-compression and bending. By employing optimization algorithms [11,12] or formulating sensitivity matrices [15,16], modal strain energy can be further used to quantify structural damage. According to the studies, the modal strain energy-based damage indicators are sensitive to local damage.…”