A test specimen of concrete and fibre concrete for the axial tension test and a tool for its mounting

摘要

The test specimen (1) is made of concrete or fibre concrete and has the shape of a quadrilateral prism having a variable cross-sectional width over its length, where the end part of the specimen (1) having a square or rectangular cross-section with the breadth (B) and the height (H), form the upper head (1.1a) and the bottom head (1.1b). Between the heads (1.1a, 1.1b), the cross-section of the prism changes along its entire length, symmetrically with respect to the transverse axis of the test specimen(1), by creating two successive reductions in the two opposite sides. Under the upper head (1.1a) and under the bottom head (1.1b), there is formed the planar reduction (1.2) bevelled at the angle of 45°, followed by the straight part (1.3) transitioning into the reduction (1.4) of a curvilinear shape with tangential connection to the shared medium part (1.5) of a constant width. The clamping device of the test specimen consists of two identical steel brackets (U1, U2) for articulated attachment of the ends of the test specimen (1). Each bracket (U1, U2) consists of the rectangular bearing front plate (2) provided, in the loading direction, with a pair of stiffeners (2.1), between which there is, at the centre of the front plate (2), formed the circular opening (2.2), into which there is embedded the circular steel ring (2.3) whose inner surface is, towards the outer circumference, conically bevelled. The ring (2.3) is fitted with the hinge pin (3) in the shape of a cylinder with a conically extending bottom sub-assembly, whose upper part is adapted for clamping into the press. The two separate straight side plates (4), which are, before fitting the test specimen (1) into the testing machine, clasped around the heads (1.1a, 1.1b) of the test specimen (1), are part of each bracket (U1, U2). Each of the side plates is provided with a pair of longitudinal stiffeners (4.1). The top part of the side plates (4) is connected to the flange (4.2) for fitting on the front plate (2). The bottom part of the side plates (4) is provided with the cylindrical end (4.3) for the line support of the test specimen (1) in the planar reduction (1.2). The side plates (4) are fixed outside the surface of the test specimen (1) with the clamping threaded rods (5).