Experimental Study on Dynamic Fracture Properties of Concrete under Small Eccentricity Loading

• Published in: Journal of materials in civil engineering 2024-08, Vol.36 (8)
• Main Authors: Yu, Zhenpeng, Zhan, Xiongfei, Chang, Yuanhao, Hai, Lu
• Format: Article
• Language: English
• Subjects: Concrete; Concrete properties; Concrete structures; Crack initiation; Crack propagation; Cracking (fracturing); Digital imaging; Displacement; Earthquake loads; Eccentric loads; Eccentricity; Fracture testing; Fracture toughness; Load; Mechanical properties; Peak load; Strain rate; Technical Papers
• ISSN: 0899-1561; 1943-5533
• DOI: 10.1061/JMCEE7.MTENG-17503

AbstractIn practical engineering, concrete structures usually work with cracks, and seismic loads often deviate from the center of the cracks. Therefore, exploring the strain rate effect on the fracture performance of concrete under small eccentricity is of great significance. In order to explore the dynamic fracture properties of concrete under different loading positions, considering four strain rates and four eccentric displacement factors, combined with digital image correlation (DIC), a hydraulic servo machine is used to conduct three-point bending beam fracture tests on concrete. By conducting tests under different working conditions, the concrete fracturing morphology, load-crack mouth opening displacement (P-CMOD) curves, and mechanical characteristic values were obtained. The influence of strain rate and loading position on concrete fracture properties is analyzed. The results show that the initial fracture load and unstable load of concrete fracture increase with the increase of loading eccentricity displacement and loading strain rate. A model for the relationship between concrete unstable load, loading eccentricity, and strain rate is established based on the experimental results. Under the coupling effect of high-strain rate and high-loading eccentricity, the crack propagation speed of concrete increases sharply after reaching the peak load. The fracture toughness of concrete increases linearly with the increase of loading eccentricity and strain rate. The unstable toughness of concrete shows a trend of first increasing and is then almost unchanged with the increase of strain rate, and gradually increasing with the increase of loading eccentricity displacement. At the same loading position, the fracture energy of concrete increases with the increase of strain rate, with a maximum growth rate of 40.5%. At the same strain rate, the fracture energy of concrete gradually increases with the increase of loading eccentricity, with a maximum growth rate of 56.6%. The research results provide a theoretical basis for the initiation and development of concrete cracks under medium to low strain rates and small eccentric loads.