Test Method for Determining Process Zone Position and Fracture Energy of Concrete

Schorn, H.; Berger-Böcker, T.

doi:10.1111/j.1747-1567.1989.tb01033.x

Cited by 6 publications

(3 citation statements)

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“…https://doi.org/10.21012/FC11.092379 The softening behaviour of quasi-brittle materials like concrete and rock entails a reduction of the borne load at increasing crack opening (namely a negative stiffness), requiring a displacement-controlled test system to drive the test [7][8][9]. Nonetheless, the smooth propagation of the crack at increasing actuator displacement would imply the total stiffness of the loading frame to be larger than the negative stiffness of the fracturing sample [10,11].…”

Section: Introductionmentioning

confidence: 99%

3action: A Viable Setup For Direct-Tensile Testing Of Concrete

Felicetti,

Yarmohammadian,

Cantu

2023

Proceedings of the 11th International Conference on Fracture Mechanics of Concrete and Concrete Structures

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The experimental characterization of concrete's post-peak stress vs crack opening curve is a key aspect in many practical problems involving crack stability, like size-effect and explosive spalling of High-Performance concrete in the fire. The direct-tension test is recognized as the most straightforward solution, though the strain-softening material behaviour entails tricky issues concerning the axial and flexural stability of the test. Axial stability is impaired by the deformability of the loading frame since the traditional scheme of universal testing machines entails compression of rather long columns and bending of the crosshead and the table. The consequent deformation energy largely exceeds the dissipation capacity of the tested sample, requiring responsive closedloop control systems for smoothly driving the descending branch of the test. As regards flexural stability, several solutions have been proposed to improve the bending stiffness of the test rig, mostly based on ball bushing guiding systems or adjustable tie-rods secured to the loading platens. However, the transversal restraint to the sample may trigger parasitic shear stress, which translates into inclined fracture propagation paths and overlapping cracks. To address these multifaced issues, an innovative frameless test rig has been designed, based on three symmetrically arranged electro-mechanical jacks directly pushing the top of the sample up. The samples are short, notched cylinders (Ø=100mm, h=150mm) preliminarily glued to thick steel platens and then bolted to the bottom table and the moving head of the machine, speeding up their installation and later removal. The load is exerted through stiff load cells and pendular struts, preventing any transversal load component. The actuators are optimized for stiffness and promptness, and three parallel control loops are implemented to drive the mean opening and two orthogonal rotation components of the crack mouth. At the present stage, the prototype has been assembled and the control routines are being tested. A first series of experimental results will be included in the final presentation at the conference.

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Section: Introductionmentioning

confidence: 99%

3action: A Viable Setup For Direct-Tensile Testing Of Concrete

Felicetti,

Yarmohammadian,

Cantu

2023

Proceedings of the 11th International Conference on Fracture Mechanics of Concrete and Concrete Structures

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“…The other kind of indirect tensile test method uses the parallel load‐sharing system (Figure 1), where the concrete specimen is indirectly loaded through load transfer system [7, 9–13]. The indirect tensile tests provide several advantages over direct tensile tests for cementitious materials samples: fairly simple loading fixtures and, exact alignment is normally not required.…”

Section: Introductionmentioning

confidence: 99%

A Modified Tensile Test to Study the Behaviour of Cementitious Materials

Mallat

Alliche

2011

Strain

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We investigate the tensile behaviour of two fibre reinforced repair mortars by two direct tensile testing configurations. In the first configuration, a ball-joint loading fixture is developed such that an ideal hinge boundary condition is guaranteed. This technique allows to access to mechanical properties of the material such as the modulus of elasticity and the failure stress. However, it does not allow studying the post-peak behaviour of the materials. A new post-peak tension test is adopted using a metallic bar within the fibre reinforced repair mortar hollow sample. Bar constitute a crack stabiliser by providing extra stiffness. It can minimise or eliminate the strain energy release from the testing machine, so that a stable post-peak response can be obtained. The test method uses a digitally controlled closed-loop testing electromechanical machine and three control channels: crosshead displacement and two extensometers mounted on the test sample. A complete stress-strain curve is obtained by this method if adaptive control and test setup are chosen appropriately.KEY WORDS: adaptive control, fibre reinforced mortar, post-peak tensile test, tensile test Ó

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“…The direct tensile behaviors of concrete have been tested with several methods by scholars of various countries around the world. Some experimental experiences and reliable research achievements were acquired [1][2][3][4][5][6][7] . However, the test data of large size dam concrete specimens and wet-screening concrete specimens are deficiency.…”

Section: Introductionmentioning

confidence: 99%

Fracture Behaviors of Dam and Wet-Sreening Concrete by Direct Tensile Test

Zhao

Pang

Zhao

2008

KEM

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The emphasis of this paper is to experimentally study the fracture behaviors of dam and wet-screening concrete such as softening curve, uniaxial tensile strength , maximum crack width and fracture energy . The direct tension tests were performed on prismatic specimens with no initial notch include dam concrete specimens which size is 250mm×250mm×500mm and wet-screening concrete specimens which size is 150mm×150mm×300mm by employing a servo-hydraulic closed-loop testing machine with large stiffness. The uniaxial tensile load-strain curves, uniaxial tensile stress-strain curves, uniaxial tensile stress-deformation curves were acquired. On the basis of principle of fracture mechanics of concrete, the stress-crack width curves and the relative stress-relative crack width curves were obtained. Finally, the expressions of softening curves and fracture parameters such as , and of dam and wet-screening concrete were achieved. The relationships of the foregoing fracture parameters between dam concrete and wet-screening concrete were discussed in this paper. The achieved softening curves and fracture parameters can provide input data for the fracture simulating analysis of dam and wet-screening concrete.

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Test Method for Determining Process Zone Position and Fracture Energy of Concrete

Cited by 6 publications

References 0 publications

3action: A Viable Setup For Direct-Tensile Testing Of Concrete

3action: A Viable Setup For Direct-Tensile Testing Of Concrete

A Modified Tensile Test to Study the Behaviour of Cementitious Materials

Fracture Behaviors of Dam and Wet-Sreening Concrete by Direct Tensile Test

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