Quantification of structural damage by harnessing the principle of local force continuity

Abstract

Quantitative assessment of damage severity is important for maintaining and extending the service life of engineering structures. Traditional vibration-based methods often face challenges such as low sensitivity, strong dependence on structural details and excitation signals, and the need for global models or baseline signals. The recently developed Pseudo Excitation (PE) method enables the detection of local structural damage by utilizing high-order spatial derivatives of the measured displacement data, easing some of these constraints. However, the PE method can only pinpoint the presence of damage and outline its boundaries; it currently lacks the ability to quantify the damage severity or the profile of the damaged area. To address these limitations, this study proposes a novel damage quantification approach, referred to as Local Force Continuity (LFC) method, based on the continuity principle of local internal forces. By examining the force continuity relations near the damage boundary, we establish a correlation between the damage severity and the measured vibration responses, enabling a quantitative characterization of the damage profile. The proposed approach is first validated through numerical simulations, showcasing its remarkable ability in locating damage and identifying its shape. The effects of damage extents, excitation frequency and structural boundary conditions are systematically investigated, highlighting the effectiveness and robustness of the proposed method. Finally, experimental verification is conducted using laser doppler vibrometer (LDV) scanning. Results demonstrate that the LFC method can effectively assess damage severity. The LFC method not only retains the advantages of the PE method, but also significantly extends its capabilities in damage quantification, providing new physical insights and broadening its potential applications in related engineering fields.