lab7 - CE 497 Prestressing Materials Section 5 Hui Fan...

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CE 497 Prestressing Materials Section 5
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Hui Fan 3/5/2009
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INTRODUCTION: The objective of this experiment is to demonstrate the prestressing principle in general and the mechanical prestressing of concrete. The most important concept in this experiment is the modulus of rupture (C-78 formula: MOR = Pl/bd^2). Modulus of rupture is measured in terms of stress, and thus is expressed in units of pressure (or stress, the two being equivalent). The value represents the highest stress experienced within the material at its moment of rupture. The expected results in this experiment should be the higher prestressing applied, the larger modulus of rupture of the material. PROCEDURE: There were three beams tested in this experiment. The first beam will be tested with no prestress on it. This test is similar to ASTM C-78. The next demonstration is of a similar beam, but with an applied prestress. The prestress will be applied by the posttensioning method, by casting a plastic tube along its neutral axis and using a steel rod passed through this tube and tensioned by tightening nuts on its threaded ends. The tensile force will be measured with the transducer. The third beam will be tested in a higher level of prestressing which basically same as the second beam. The force at which the beam cracks is used to calculate the maximum tensile stress on the
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lab7 - CE 497 Prestressing Materials Section 5 Hui Fan...

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