PR18-Rebound_Hammer - 2nd level Degree in Structural and...

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2 nd level Degree in “Structural and Geotechnical Engineering” Ph.D. course in “Construction Engineering” Course of “Structural Assessment, Monitoring and Control” REBOUND HAMMER TESTING: CHARACTERISTICS AND OPERATIVE PROCEDURE Eng. Mariacristina Spizzuoco 2 nd level Degree in “Structural and Geotechnical Engineering” Ph.D. course in “Construction Engineering” Course of “Structural Assessment, Monitoring and Control” OPERATION PRINCIPLES OF THE METHOD Normative reference : EN 12504-2 of June 2001. The physical principle at the base of the inelastic collision . ± The impact of the steel hammer with the concrete surface produces a different distribution of the initial kinetic energy: an aliquot is absorbed by the concrete as plastic strain energy, while the remaining aliquot is returned to the mobile hammer which rebounds remaining aliquot is returned to the mobile hammer which rebounds for a distance proportional to the available energy. ± The necessary condition is the assumption that the concrete mass is The necessary condition is the assumption that the concrete mass is infinite with respect to the mass of the hammer. The hypothesis is acceptable because the condition of infinite concrete mass is achieved by using very small inpact masses.
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2 nd level Degree in “Structural and Geotechnical Engineering” Ph.D. course in “Construction Engineering” Course of “Structural Assessment, Monitoring and Control” OPERATION PRINCIPLES OF THE METHOD The rebound hammer uses a system of springs in order to develop the energy necessary for the collision. The rebound number depends on the rebound energy and on the characteristics of the springs’ system. The testing equipment has to be supplied with a system to verify the calibration as, after a long use, the springs may be affected by a modification of their elastic constants. 2 nd level Degree in “Structural and Geotechnical Engineering” Ph.D. course in “Construction Engineering” Course of “Structural Assessment, Monitoring and Control” REBOUND HA MMER INSTRUMENT The rebound hammer consists of a cylindrical main body containing a moving steel striking mass (i.e. a steel hammer). The steel hammer is driven by a spring and when released strikes a steel plunger in contact with the concrete surface.
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2 nd level Degree in “Structural and Geotechnical Engineering” Ph.D. course in “Construction Engineering” Course of “Structural Assessment, Monitoring and Control” REBOUND HAMMER INSTRUMENT The plunger in contact with the surface is pushed until the achievement of the limit value of its stroke. The steel hammer, returned by the spring, strikes the surface and rebounds for a strikes the surface and rebounds for a distance, by dragging a slider which allows to assess the rebound number on a linear scale.
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PR18-Rebound_Hammer - 2nd level Degree in Structural and...

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