Effect of different boundary conditions in direct tensile tests: experimental results

The effects of the kinematic 'constraints' of a direct tensile test on the complete load-displacement response in tension of concrete specimens were e xamined from tests with imposed uniform displacement (fixed platens) and fr om experiments with free rotation rotating platens through a closed-loop te sting system. Cylindrical specimens and prismatic specimens were considered . The tests were monitored with an interferometric strain measurement (elec tronic speckle pattern interferometry). A notable outcome of the experiment s is that the fixed platens imposed a more uniform strain field with higher peak loads. Also the post-peak branch had a shape that depends on the boun dary conditions under which the tests were performed.