Large-scale fully graded concrete shaft tensile testing machine

Abstract

The invention relates to a tester capable of carrying out large-sized fully graded concrete axial-tension tests. The tester mainly comprises such members as an upper frame beam (1), a lower frame beam (5), two uprights (4), a main steel beam (2), two magnetorheological dampers (8), two damper dowel bars (3), an upper bearing rod (41), a middle bearing rod (42), a lower bearing rod (6), an upper concrete test piece connecting steel plate (9), a lower concrete test piece connecting steel plate (10), a spherical hinge (11), a hydraulic actuator (19) and the like. During a test, real-time variation of the rigidity of the tester is realized by adjusting the magnitude of the force output of each magnetorheological damper in real time, so that the resilience of a test system caused by load drop at the descending segment of a concrete tensile curve can be restrained, thereby guaranteeing stable fracture of the test piece; such an axial-tension tester capable of carrying out axial tension stress-deformation overall tests of the large-sized fully graded concrete overcomes the problems of insufficient rigidity and uncontrollable elastic energy release process that a common tester and a changed tester with parallel-connected rigid elements may have.

Description

technical field [0001] The invention mainly relates to a concrete testing machine, which is a testing machine for full-range axial tension test of large-scale fully-graded concrete, especially a test device capable of realizing a stable and controllable fracture process of large-scale fully-graded concrete specimens , belonging to the technical field of civil engineering. Background technique [0002] Under the condition that the construction of high dams around the world is slowing down, there are still a large number of high concrete dams under construction and proposed in my country. 305m), Xiaowan (294.5m), Xiluodu (285.5m), Baihetan (284m), etc., the dam height has exceeded the current design code, and there is no precedent at home and abroad for reference, and the terrain in the area is steep and the geological conditions are complex. The earthquake intensity is high and the environment is harsh, which increases the difficulty of design. The axial tensile stress-defor...

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Problems solved by technology

Using rigid components to improve the stiffness of the testing machine has two disadvantages: (1) When the ultimate tensile value of the specimen is large, because the additional rigid component bears more loading force of the testing machine, the loading force of the testing machine on the concrete specimen (2) For concrete with high brittleness, the curve of its descending section is relatively steep, which requires a high stiffness of the testing machine, which is often difficult to achieve

At present, these modified testing machines with rigid components connected in parallel on ordinary testing machines can achieve good results in the testing of small-sized concrete specimens, but the testing of large-sized fully graded concrete components is obviously insufficient, and these testing machines cannot guarantee During the whole experiment process, the elastic energy stored in the testing machine will not be released suddenly, so as to achieve the stable failure of the concrete specimen

Therefore, it is difficult to obtain the full axial tensile stress-deformation curve of fully graded concrete on a common testing machine.

Hohai University used the self-developed test device that can carry out the full curve of axial tensile stress-deformation of fully graded concrete, but the stiffness adjustment ability of the test machine is limited, and there is a phenomenon of lost motion when using medium oil dampers. Tsinghua University adopted Similar results were obtained from the direct test on the INSTRON 8056 rigidity testing machine. However, due to the high cost of the testing machine, the limit load and headroom of the testing machine are limited, and the headroom is too small, so only the steel plate attached to the end can be used for the axial tension test, which is very easy. End failure occurs, causing test failure

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