Concrete multi-factors durability experimental device under bent tension stress and environment coupled action

Abstract

In a concrete multi-factor durability experimental device under the action of the bend-pulling stress and the environment coupling, lower part of the pulling rod (6) is connected to a lower pressing board (9); the upper part of the pulling rod (6) presses a stress sensor (1) on the pulling board (2) via the screw cap (3) traversing the upper pressing board (5) and pulling board (2); a spring (4) is arranged between the pulling board (2) and the upper pressing board (5); concrete test pieces (8) are arranged between the upper pressing board (5) and the lower pressing board (9); a mat stick (7) is arranged between the concrete test pieces and between the concrete test piece (8) and the upper pressing board (5) or the lower pressing board (9); two sides of the concrete test piece (8) are arranged with a constant force holding meter (10); the constant force holding meter (10) is connected to the non-metal supersonic testing meter (11). The device is suitable for the big size concrete test piece, retaining the no stress loosing state in the process of loading in a long term.

Description

technical field [0001] The invention relates to a multi-factor durability experiment method and device for concrete under the coupling action of bending-tensile stress and environment, which belongs to the concrete durability testing technology. Mainly used in construction and transportation fields. Background technique [0002] For half a century, accidents of premature failure and shortened life of concrete structures due to insufficient durability of concrete structures have continued to increase, especially major projects such as dams, roads, bridges, ports, and high-rise buildings that have not reached the design period. Accidents of destruction occur from time to time, causing huge economic losses and casualties. The research report of the Chinese Academy of Engineering shows that in China, the direct economic loss of concrete structures caused by the corrosion of steel bars is as high as 100 billion yuan per year. Although the research on the durability of concrete ...

AI Technical Summary

Problems solved by technology

The advantage of the lever loading device is that the principle is simple, the load controllability is relatively good, and it is not affected by temperature; the disadvantage is that the loading efficiency is relatively low. When loading 50% bending stress of a 40mm×40mm×160mm specimen, the length of the lever needs 0.6 meters, which takes up a lot of test space. When multi-factor durability tests such as loading-freeze-thawing and loading-carbonization are carried out at the same time, the test box of the test instrument can hardly accommodate it. If the length of the lever arm is reduced, the load accuracy will be reduced.

The advantages of the rod loading system are easy to operate, the device is small in size, and can be adapted to existing standard carbonization boxes and freeze-thaw testers and other durability devices to achieve stress-environment (carbonization, freeze-thaw, etc.) coupling; the disadvantage is the stress wrench The control accuracy is low, and it is easily affected by the corrosion of bolts, etc., which further reduces the load control accuracy; the stress will relax greatly during the long-term load process

In addition, this method is not suitable for loading in freeze-thaw tests, because the thermal expansion and contraction of the tie rods will cause large errors when the temperature changes. Errors caused by deformation and surface peeling cannot be ignored, and the bolts tightened with a stress wrench may be immersed in water or solution during the freezing and thawing process, which will cause changes in the friction coefficient of the bolts. A small change in the friction coefficient will cause a large The load changes, and the stress wrench cannot eliminate the error caused by it

The spring-loaded device is currently used by many researchers at home and abroad. This device was invented by Professor Sun Wei of Southeast University and Dr. Mu Ru. Its advantages are simple principle, small size, space-saving, and can realize freeze-thaw, dry-wet, carbonization , chemical corrosion and other multi-factor tests, and three test blocks can be loaded at the same time at one time, which greatly improves the efficiency; the disadvantages are: (1) the size of the applicable concrete test piece is too small, only 40×40×160mm, which is not The standard small test piece cannot fully reflect the original properties of the concrete material in the actual project, which reduces the uniformity of the test data and the conformity of the actual project; (2) limited by the distance between the tie rod and the side of the test piece, it cannot Directly conduct continuous dynamic and ultrasonic performance tests on the concrete specimens in the loaded state (that is, without unloading). For concrete specimens reaching a certain age, the index test must be performed after unloading, and reloading after the test is completed, which is not sufficient. The damage failure state under reactive loading state; (3) In addition, although spring loading can relieve part of the stress relaxation problem through its own deformation to a certain extent, it cannot completely eliminate

[0005] The above-mentioned shortcomings severely limit the wide application of bending-tensile stress loading devices in concrete multi-factor durability experiments.

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