Concrete I-II compound crack fracture performance test method

Abstract

The invention relates to a concrete I-II compound crack fracture performance test method, and belongs to the technical field of physical test methods. According to the method, an upright and sloping three-point bent beam is adopted for testing, and on a fracture tip, a central symmetry mode is adopted for fixing a clamping extensometer cushion block, so that I-type failure crack opening displacement in a I-II compound fracture failure process is determined; in a calculation process, with the help of a double K fracture theory, a fracture angle function f(theta) is introduced to obtain compoundcrack fracture toughness under different fracture angle conditions, and a more accurate concrete I-II compound fracture coherency equation can be built. By means of the method, safety assessment of the structure fracture performance is achieved, an existing finite element numerical simulation technology is broken through, accurate judgement of the common compound fracture mechanical performance is completed, and a basis is provided for the long-term stability and the fracture toughness of a concrete crack.

Description

technical field [0001] The invention relates to a concrete performance test method, in particular to a concrete I-II composite type crack fracture performance test method, which belongs to the technical field of physical test methods. Background technique [0002] Engineering practice shows that due to the cement hydration reaction of concrete during the molding process and the existence of low tensile strength of concrete materials, many micro-cracks or macro-cracks are inevitably generated inside the concrete. Under the action of load or other external factors , the cracks continue to expand or even penetrate, which will easily have an important impact on the service life, overall safety and durability of the concrete structure. Therefore, the research on the fracture behavior of concrete has become one of the important basic technical indicators for evaluating the safety of concrete structure engineering. one. [0003] The research on concrete fracture has been carried o...

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Problems solved by technology

Moreover, the test method stipulated in the "Hydraulic Concrete Fracture Test Regulations" is mainly a judgment test method for type I cracks, and cannot be used as a fracture failure basis for composite cracks.

[0011] (2) The current research on Ⅰ-Ⅱ composite cracks mainly uses four-point shear beams, but limited by the test methods and research methods, the method used to calculate the fracture toughness is basically finite element numerical simulation In the existing nonlinear fracture theory of concrete, there is no fracture parameter evaluation method related to Ⅰ-Ⅱ composite cracks, which is an area to be studied at present.

[0012] (3) The fracture and failure process of concrete is actually a relatively complicated process

[0013] (4) The four-point shear method used at this stage to test the I-II composite crack method, in the test process, when the load reaches the extreme value, the failure process is relatively rapid, that is, it occurs immediately after the specimen reaches the maximum bearing capacity Instability damage, a relatively complete load-opening displacement failure curve cannot be obtained, and the test shows a sudden drop in the descending section of the load-deflection curve. The calculation of fracture energy based on this is also inaccurate. It is urgent to develop and design a suitable Test method for compound type cracks in concrete Ⅰ-Ⅱ

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