Concrete tensile creep testing device and concrete shrinkage stress creep testing method

Abstract

The invention discloses a concrete tensile creep testing device which comprises a bracket, an upper perforated-articulated chuck, a lower perforated-articulated chuck, a perforating test piece, a deformation gauge and a balance weight load, wherein the two perforated-articulated chucks which are connected with the perforating test piece are respectively hung on the bracket and are connected with the balance weight load, so that the testing device can be formed. A concrete shrinkage stress creep testing method adopts a standard creep chamber and natural environmental condition, is restrained by complete or non-complete constraint stiffness, adopts loading ways of 'step loading' and 'follow-up loading', is carried out under the shrinkage threshold value and fixed age period loading control condition, and can be used for testing the concrete shrinkage stress creep. After the testing device and the testing method are adopted, the problems of connection between the concrete test piece and the chucks, physical alignment and load loss can be solved, and the test operability can be improved; furthermore, creep and strain can be tested gradually, so that more creep behaviors and performance problems can be researched; particularly, the concrete shrinkage stress creep test can be realized in the natural environment.

Description

technical field [0001] The invention discloses a concrete tensile creep test device and a concrete shrinkage stress creep test method; in particular, it refers to a concrete tensile creep test device and a concrete shrinkage stress creep test method; it belongs to the concrete test in the field of civil engineering Technical field, especially concrete tensile creep test technology. Background technique [0002] Concrete in structures often cracks due to shrinkage and restraint. Creep is a key issue in the shrinkage and cracking resistance of structural concrete. In recent years, the research has also been in-depth. The view that "the tensile creep performance of concrete is different from the relatively mature compressive creep performance" has been accepted by the industry. The research work has also made progress, and the creep behavior of concrete under shrinkage stress has the mechanical characteristics of load and creep time-varying, as well as the particularity of con...

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Problems solved by technology

Due to the adjustable characteristics of hydraulic pressure, this method can also carry out shrinkage stress creep test in theory, but this kind of method affects the practical application due to the long-term pressure stabilization problem of hydraulic pressure (cylinder). 1) The same load instability problem

[0008] (5) Others, pure bending-tension method - when the concrete beam is subjected to pure bending load, the part under the neutral axis of the concrete beam is in a state of tensile stress, and the tensile creep research is carried out. This method is suitable for the creep research of prestressed concrete beams It is of great significance. Zhang Haobo of Xi'an University of Technology obtained meaningful results in his research field by using this method, but the tensile and compressive stresses are distributed throughout the concrete beam section, and there is a tensile stress gradient distribution in the tensioned part. There are limitations in the extensibility; the oil pressure-internal expansion method-make the concrete into a hollow cylinder (cylinder) specimen, seal and connect the oil pipe, and make the concrete circular by adding the pressure generated by the pressure liquid (hydraulic pressure, gas-air pressure). The expansion of the cylinder is under tension to study the tensile creep of concrete. A.D. Ross carried out this method. There is also a gradient in the internal tensile stress of concrete. In addition, the sealing and penetration resistance of the test piece have a great influence on the success rate of the test. This method is not widely used.

(2) Pre-embedded anchorage type (see Figure 5-b), the steel plate is bonded to the concrete through pre-embedded anchorage steel bars, or additional adhesive treatment, and the tensile load is transferred. Researchers from Australia-Monash University adopt this method The tensile test of fiber concrete is carried out, but the effect of this kind of clamp itself on the adjustment of eccentricity is limited, and it is necessary to add universal joints to improve the influence of adjusting eccentricity

However, the tests conducted by the applicant of this patent show that the adhesives supplied in the domestic market have a long curing time, and the cohesive force often cannot meet the requirements of the design value of the tensile creep load, which makes the actual operation difficult, especially the early creep test of concrete. more prominent

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