Crack Detection in Reinforced Concrete Beams Using Improved Displacement Influence Line Method

• Published in: International journal of civil engineering (Tehran. Online) Vol. 23; no. 9; pp. 1791 - 1811
• Main Authors: Ha, Tuan Minh, Dang, Ngoc-Thuy-Vy, Tran, Manh-Hung, Ho, Duc-Duy
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.09.2025; Springer Nature B.V
• Subjects: Civil Engineering; Engineering; Research Paper; Structural health monitoring; Damage detection; Displacement influence line; Reinforced concrete beam; Crack
• ISSN: 1735-0522; 2383-3874
• DOI: 10.1007/s40999-025-01115-y

This paper proposes an improved method for detecting, locating, and quantifying damage levels in reinforced concrete beams subjected to moving loads, using displacement influence line data. The subject of this study is a reinforced concrete beam with a span of 2.2 m, based on an actual experimental setup from a previous study. The experiment was re-simulated using the finite element method, and the simulation results were compared with experimental data to validate the model’s accuracy. In this study, the degree of beam damage is defined as the length of the crack zone on the underside of the beam, which develops under varying levels of static loading. To assess the damage, displacement data for both the undamaged (reference) and damaged states of the beam were extracted from the computational model. The Root Mean Square Deviation (RMSD) was then calculated to evaluate the correlation between the displacement influence lines for the two states. The findings indicate that the proposed indicators (i.e., A, B, C, K) effectively assist in identifying the presence and location of damage. This study also improves the RMSD index by incorporating standardization, graphical plotting, damage zoning, and damage threshold determination to assess the severity of damage. The diagnostic results for the three midspan failure scenarios showed a C rating greater than 90% and a K value of ≥ 0.8, indicating very good consensus. For non-midspan damage, the C rating exceeded 91%, with similar consensus levels. In a further verification test examining the effect of data collection points on diagnostic accuracy, the RMSD-standardized method achieved A = 95.5%, B = 100%, C = 96.8%, and K = 0.922, demonstrating high reliability. All test scenarios in this study achieved an accuracy greater than 90%, with strong agreement between simulated and experimental results.