Mpalaskas Anastasios C, Kytinou Violetta K, Zapris Adamantis G, Matikas Theodore E
Laboratory of Reinforced Concrete and Seismic Design of Structures, Department of Civil Engineering, School of Engineering, Democritus University of Thrace (DUTH), 67100 Xanthi, Greece.
Department of Materials Science and Engineering, University of Ioannina, 45110 Ioannina, Greece.
Sensors (Basel). 2024 Aug 31;24(17):5668. doi: 10.3390/s24175668.
Fire incidents pose significant threats to the structural integrity of reinforced concrete buildings, often necessitating comprehensive rehabilitation to restore safety and functionality. Effective rehabilitation of fire-damaged structures relies heavily on accurate damage assessment, which can be challenging with traditional invasive methods. This paper explores the impact of severe damage due to fire exposure on the mechanical behavior of steel-fiber-reinforced concrete (SFRC) using nondestructive evaluation (NDE) techniques. After being exposed to direct fire, the SFRC specimens are subjected to fracture testing to assess their mechanical properties. NDE techniques, specifically acoustic emission (AE) and ultrasonic pulse velocity (UPV), are employed to assess fire-induced damage. The primary aim of this study is to reveal that AE parameters-such as amplitude, cumulative hits, and energy-are strongly correlated with mechanical properties and damage of SFRC due to fire. Additionally, AE monitoring is employed to assess structural integrity throughout the loading application. The distribution of AE hits and the changes in specific AE parameters throughout the loading can serve as valuable indicators for differentiating between healthy and thermally damaged concrete. Compared to the well-established relationship between UPV and strength in bending and compression, the sensitivity of AE to fracture events shows its potential for in situ application, providing new characterization capabilities for evaluating the post-fire mechanical performance of SFRC. The test results of this study reveal the ability of the examined NDE methods to establish the optimum rehabilitation procedure to restore the capacity of the fire-damaged SFRC structural members.
火灾事故对钢筋混凝土建筑的结构完整性构成重大威胁，通常需要进行全面修复以恢复安全性和功能性。火灾受损结构的有效修复在很大程度上依赖于准确的损伤评估，而传统的侵入性方法在这方面可能具有挑战性。本文利用无损检测（NDE）技术探讨了火灾暴露造成的严重损伤对钢纤维混凝土（SFRC）力学性能的影响。在直接暴露于火灾后，对SFRC试件进行断裂试验以评估其力学性能。采用无损检测技术，特别是声发射（AE）和超声脉冲速度（UPV）来评估火灾引起的损伤。本研究的主要目的是揭示AE参数，如振幅、累计撞击次数和能量，与火灾导致的SFRC力学性能和损伤密切相关。此外，在整个加载过程中采用AE监测来评估结构完整性。AE撞击的分布以及特定AE参数在加载过程中的变化可作为区分健康混凝土和热损伤混凝土的有价值指标。与UPV与弯曲和压缩强度之间已确立的关系相比，AE对断裂事件的敏感性显示了其现场应用的潜力，为评估火灾后SFRC的力学性能提供了新的表征能力。本研究的试验结果揭示了所研究的无损检测方法确定最佳修复程序以恢复火灾受损SFRC结构构件能力的能力。
