(NBR 9607-1986), American Code (ACI 318-2002), Australian Code (AS 3600-2001), Spanish Recommendations (EHE-1998) and European Recommendations (Rilem TBS-2-1984
Cracks that form at the interfaces between masonry structures are common uncontrolled occurrences in buildings. Numerous methods have been proposed by the construction industry to address this problem. Cracks continuously form in the joints between concrete columns and masonry infill walls. In this study, the most common methods for preventing these types of cracks were evaluated in laboratory experiments. Column masonry models were constructed using different types of joints between concrete columns and masonry infill walls, such as steel bars and steel mesh. The efficiency of each type of joint method was evaluated by performing direct tensile tests (pullout tests) on the models and monitoring the evolution of the crack opening in the joint between the column and wall, as a function of load applied to the model. The results from this study indicate that the model composed of "electrowelded wire mesh without steel angles" is the best model for controlling cracking in the joints between concrete columns and masonry infill walls.
Eunice Sumie Ando et al.
ResumoNesse trabalho, é avaliada a técnica de reforço à flexão de vigas de concreto armado pelo acréscimo de altura no banzo comprimido. Duas vigas de concreto armado, com dimensões e armaduras, transversal e longitudinal, idênticas foram executadas. Aos vinte e oito dias de idade, uma dessas vigas foi reforçada, pelo acréscimo de uma camada de concreto de alta resistência ao banzo comprimido. Uma terceira viga foi executada com as características finais da viga reforçada anteriormente, com ambos os concretos sendo executados em uma única etapa. Ao final, o comportamento, até a ruptura, das três vigas foi analisado, comprovando-se a eficiência da técnica de reforço proposta.Palavras-chave: Reforço à flexão, vigas, concreto armado.
Abstract
In this paper the technique of strengthening reinforced concrete beams to prevent the bending phenomenon by increasing the thickness in the compressed
This paper presents the experimental results of a study carried out to investigate the performance of small scale concrete columns retrofitted with unidirectional carbon fiber-reinforced polymer (CFRP) in fire situation. This study aims at the effectiveness of CFRP through the contrast test. In order to observe the residual compressive strength, the specimen was heated to a target temperature and mechanically tested under axial compression. Other similar heated specimen was cooled down to the room temperature and mechanically tested too. This procedure was repeated by temperatures of 200oC, 300oC, 350oC, 400oC, 450oC, 500oC, 600oC, 700oC, 800oC and 1050oC. The heating inside the furnace was controlled in such a way that the average temperature in the furnace followed the standard time-temperature curve, ISO 834 [1]. The experimental results comproved that, due to low temperature resistance, the CFRP systems are not capable of safely and adequately enduring fire for any substantial period of time. This study evaluated a supplementary residual compressive strength of CFRP systems after cooling down to the room temperature. Finally, this study should benefit CFRP-fire research efforts by providing a similitude relationship for the testing of full-scale and small-scale specimens.
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