Abstract
Neste trabalho são apresentados os resultados experimentais de ensaios em ligações viga-pilar de concreto armado realizados na Escola de Engenharia de São Carlos - USP. Os referidos resultados experimentais concentram-se nas rotações relativas entre os elementos viga e pilar, importantes para a determinação da relação momento-rotação das ligações e da caracterização do comportamento semi-rígido das mesmas. Os dados experimentais foram obtidos a partir de ensaios de ligações viga-pilar de extremidade. A influência da resistência à compressão do concreto e da taxa de armadura transversal na região dos nós de pórtico sobre as rotações relativas foi analisada. Os resultados experimentais foram confrontados com o modelo teórico proposto por Ferreira [1] para ligações com engastamento parcial, permitindo uma avaliação da porcentagem de engastamento alcançada pelas tipologias de ligações monolíticas abordadas neste trabalho.
Highlights
1.1 Initial considerationsIn current structural analysis for cast in situ concrete structures, beam-column connections are considered as fully rigid, and there are not any relative rotations between the beam and column elements
The good correlations between theoretical results and experimental results obtained in a study at the Engineering School of São Carlos (University of São Paulo) provide a good indication that the model proposed by Ferreira [1] allows the estimation of the percentage of partial restriction achieved by reinforced concrete beam-column connections, including monolithic connections
It should be underlined that both concrete tensile strength and the bond-slippage behavior of the longitudinal reinforcement are related to the concrete compressive strength
Summary
1.1 Initial considerationsIn current structural analysis for cast in situ concrete structures, beam-column connections are considered as fully rigid (monolithic), and there are not any relative rotations between the beam and column elements. The first is related to moment redistribution, which is caused by cracking in concrete and by yielding of longitudinal reinforcement in the support region, and possesses values limited by the Brazilian Code (ABNT NBR 6118) [2] for linear analyses with redistribution The latter is not directly related to the type of structural analysis (linear, linear with redistribution, plastic, non-linear), but rather with the most realistic representation of the conditions of connection between beam and column, in other words, the condition between the fixed and pinned condition. Among the number of variables that influence beam-column joints, the most important are concrete compressive strength and joint transverse reinforcement, because they are directly related to joint shear strength – a parameter that governs the capacity of the connection Another variable that can affect beam-column joint behavior and which deserves more attention is the normal force of the column. Experimental investigations and numerical simulations with reinforced concrete exterior beam-column connections carried out by Haach [3] indicate that the increase in normal force reduces the joint capacity, making the failure of the connections more brittle, but on the other hand, improving the anchorage conditions of tensioned beam bars
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