Abstract
The tensile properties of plain concrete are very important for the concrete structural design, and the complete tensile stress-strain curve is essential for creating accurate and reliable designs, especially when considering special load cases such as earthquakes and impacts. To study the complete tensile stress-deformation response of plain concrete, the direct tension tests were conducted on a novel thermal tensile testing machine (TTTM), which was reformed from a hydraulic universal testing machine (UTM). Acoustic emission (AE) technology was applied to monitor the damage process of plain concrete in tests. The TTTM was powered by the thermal expansion of loading columns, and had a stiffness similar to the specimen, thus eliminating the potential AE noises in the UTM, and simulating the rapid fracture process in real concrete structures. A static-dynamic acquisition system was established to obtain the complete tensile stress-strain curves, of which the data before and at the fracture moment were respectively acquired by the static acquisition system and the dynamic acquisition system. The AE technology is a useful approach to analyze the damage process of concrete, and makes it feasible to determine the damage state and the fracture location of the specimen in real time.
Highlights
The tensile properties of concrete materials are indispensable for the assessment and design of concrete structures
To study the complete tensile stress-strain response of plain concrete, a tensile testing machine (TTTM) for the direct tension test was developed by reforming a conventional hydraulic universal testing machine (UTM), and its stiffness was close to the specimen
Acoustic emission (AE) technology and a static-dynamic acquisition system were applied in the tests
Summary
The tensile properties of concrete materials are indispensable for the assessment and design of concrete structures. The complete tensile stress-strain curve of plain concrete, especially the softening response, is necessary when accessing the structural safety of concrete buildings subjected to various load cases. Studying the complete tensile stress-deformation response of concrete is of significance in concrete structural engineering. The tensile softening response of concrete is the most difficult part to acquire in the complete tensile stress-strain curve. The reason for this is that the concrete, as a quasi-brittle material, is easy to fall into an unstable cracking state when the energy released by concrete structures or test machines is greater than the energy material needed to crack stably
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