CONCRETE PRESTRESSING

Author: LUIZAGA PATIÑO ALFREDO MARTÍN.
Year: 2004.
University: POLITÉCNICA DE MADRID [www.upm.es].
Place of defense: E.T.S.I. DE CAMINOS, CANALES Y PUERTOS.
Place of preparation: E.T.S.I. DE CAMINOS, CANALES Y PUERTOS.

Summary: The reinforcement of structural elements of reinforced concrete subjected to bending, by incorporating additional armor by gluing strips of steel with Epoxy resin has been developed with considerable success since the seventies, both in appearance and in the achievements research gradually coming to a widespread use. The emergence of new materials to alternative bands deacerocomo gangs of polymers reinforced with carbon fiber (PRFC), with resistance to traction 2900 N/mm2, with a modulus of elasticity of 150,000 N/mm2, a lengthening of ruptured 1.4% and density of 1.6 kg/dm3, which represents one fifth of the weight of steel and resistance 6 times higher. Another material suffers incorporation in the world of construction are the tissues of carbon fiber (CF), in the form of leaves of great length with a resistance to traction above 3,400 N/mm2 and the modulus of elasticity of 230,000 N / mm2, with a lengthening of breaking 1.5%. The mechanical properties of these materials are attractive for the reinforcement to replace steel bands. This thesis analyzes and compares the mechanical behavior of reinforced concrete beams reinforced with steel bands, bands PRFC and tissues of CF. The tests were conducted in the Laboratory of Building Materials of the College of Engineers of Roads, canals and ports. It has conducted an exhaustive study of the mechanical properties of each material used in the manufacture of reinforced concrete beams, as well as employees in the three booster systems. Placing particular emphasis on the study of adhesives to use appropriate for this purpose. The design of the beams correspond to the parameters defined by EHD ductility, placing the time of exhaustion near the lower limit of this parameter, with the aim of having a route to the collapse of section reinforced. The tests have established the moments of exhaustion, moments of rupture, tension and the efforts that influence. Moreover, according to the system booster, we have identified different mechanisms of cleavage and how to prevent, so that the rupture either type ductile. It states further that the high resistance of new materials booster is not possible exploit in its entirety, by the incompatibility between the strains posed unit concrete and carbon fiber. We concluded that strengthening structural elements of reinforced concrete subjected to bending, it is equally effective in using the three systems booster. That for the better use of reinforcements and give ductility element, it is possible to incorporate an element of tension diffuser on the ends, taking advantage of the flexibility of the fabric of FC.

Author: BENÍTEZ BAENA JOSÉ MARÍA.
Year: 2006.
University: CASTILLA-LA MANCHA [www.uclm.es].
Place of defense: E.T.S. DE INGENIEROS DE CAMINOS, CANALES Y PUERTOS.
Place of preparation: E.T.S. DE INGENIEROS DE CAMINOS, CANALES Y PUERTOS.

Summary: The fabrication of structural elements is increasingly important in the design and construction of structures and construction of civil works. An example of these structural elements are the joists and semiviguetas of prestressing concrete with wire grafilados widely used in forged construction. In parts of prestressing concrete, the bond between the concrete and steel is responsible for its proper functioning. When used as active armor wire grafilado, the bond is favored by the increase in diameter of wire produced by the effect Poisson and compression that grafilas exerted on the concrete, trying to slide the wire during the destesado. This work aims to improve understanding of the phenomenon bond between steel and concrete, while producing a small step in order to determine an effective way to the length of transmission elements prestressing concrete. To this end have been carried out the following tasks: 1 .- We have developed an analytical model, which has taken into account the effect Poisson, adherent to simulate the behavior of structural elements pretensados with wires grafilados. This model is based on geometric and mechanical parameters measured experimentally and physical sense. 2 .- It has been designed with an essay test tubes with concrete prestressing wire grafilado, which allows to quantify the maximum tangential stress and its evolution throughout the process destesado. The test tubes have been developed with two sidings and three types of depth grafila. 3 .- It has designed a test procedure, using test tubes with concrete prestressing wire grafilado, which allows to study the evolution of the angle dilatancia of intercara acero-hormigón during destesado wire. The test tubes have been developed with three depths grafila. 4 .- It has developed a three-dimensional numerical model can reproduce the behavior adherent elements of prestressing concrete. This model has been validated by the test results of the determination of tension grip and allowed a better interpretation of test results. The proposed model is based on geometric and mechanical parameters measured experimentally and physical sense.