Proposed damage identification technique using frequency sensitivity functions

Structural damage detection is essential for ensuring the safety and functionality of civil infrastructure. Existing vibration-based methods often struggle to accurately localise damage and estimate its severity using natural frequency data alone. This study introduces a novel damage identification technique that utilises sensitivity functions of the structure’s natural frequencies to determine both damage location and severity. Unlike conventional methods, the proposed approach extracts spatial information directly from frequency shifts without requiring extensive modal data. Sensitivity functions were developed through finite-element analysis of single-span reinforced concrete beams and incorporated into a custom computer program designed to solve the resulting system of equations. The method was validated using experimental data from prior studies on steel cantilever beams, demonstrating its effectiveness in identifying single damage locations. In addition, the technique was tested on a finite-element model of the El-Salam cable-stayed bridge in Egypt, where it successfully detected damage near mid-span cables. The method relies solely on frequency measurements, offering a low-cost, efficient tool for structural health monitoring. While current applications are limited to single damage locations, future research will explore the extension of this approach to multiple damage scenarios and more complex structural systems.