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In this paper, a nonlinear finite element analysis of slab-beam-column connection in precast concrete structures is presented. The detailed experimental results of the full-scale connection have been discussed in a different paper. However, due to the complexity of slab-beam-column connection and the unique features of the tested specimen, the numerical study was carried out to better understand the structural behavior. The internal connection was comprised by corbels, dowels and a continuity bars passing though the column. The FE model was validated using the experimental results of the precast concrete connection and it showed good capacity to represent the behavior observed in laboratory. A parametric analysis was conducted with the variation of the diameter of the continuity bars and the properties of the cast in place concrete. As a result of this study, some information about stresses, strains and displacements not obtained experimentally was determined in the numerical simulation and, with the parametric analysis it was concluded that the diameter of the continuity bars had more influence in the precast concrete connection capacity than the concrete compressive strength.

This paper presents an experimental study on the behavior of composite floor slab comprised by a new steel sheet and concrete slab. The strength of composite slabs depends mainly on the strength of the connection between the steel sheet and concrete, which is denoted by longitudinal shear strength. The composite slabs have three main failures modes, failure by bending, vertical shear failure and longitudinal shear failure. These modes are based on the load versus deflection curves that are obtained in bending tests. The longitudinal shear failure is brittle due to the mechanical connection was not capable of transferring the shear force until the failure by bending occurs. The vertical shear failure is observed in slabs with short span, large heights and high concentrated loads subjected near the supports. In order to analyze the behavior of the composite slab with a new steel sheet, six bending tests were undertaken aiming to provide information on their longitudinal shear strength, and to assess the failure mechanisms of the proposed connections. Two groups of slabs were tested, one with 3000 mm in length and other with 1500 mm in length. The tested composite slabs showed satisfactory composite behavior and longitudinal shear resistance, as good as well, the analysis confirmed that the developed sheet is suitable for use in composite structures without damage to the global behavior.

In this paper an experimental research on beam–column internal connections is reported. The studied connection consisted of a concrete filled steel tubular column and steel beams with endplates joined by embedded bolts. The slab was also considered in the prototype, comprising the major focus of the experimental program wherein the influence of the reinforcement ratio and the continuity of bars was analyzed. An innovative detail using steel sleeves is proposed to achieve the continuity of the slab reinforcement. The behavior of the proposed connection was compared to the behavior of the connection with conventional system with bars welded on the steel tube. Three large-scale specimens subjected to cyclic loading have been tested and their responses measured and analyzed. The results showed the good behavior of the proposed connection, mainly avoiding transfer of forces to the steel tube. Regarding the influence of the slab reinforcement ratio, it was observed a better behavior of the connection with higher ratio, preserving the initial stiffness after the loading cycles.

This paper addresses the behaviour of composite beam-column connections that consist of concrete-filled steel tubes (CFTs), beams, bolts, endplates, and slabs. The composite connection under study was simulated with a tridimensional numerical model using the Diana software, which is based on the finite element method (FEM). A reference model was validated with previously obtained experimental results and was used as a reference for the parametric study. The parameters considered in the study included the bolt diameter, stud spacing, and slab reinforcement ratio. Analysis of the results led to the conclusion that changing a single parameter did not increase the connection stiffness because the failure was transferred to other structural elements in the connection. Instead, the connection dimensioning procedure should consider the entire set of parameters to guarantee the structure's security. Finally, the composite connection's behaviour is discussed in detail, and recommendations for the design are presented.

No presente trabalho foi analisado o comportamento de ligações viga-pilar em estruturas mistas de aço e concreto com o auxílio de simulação numérica e experimentação. A simulação numérica foi realizada no programa DIANA, baseado no método dos Elementos Finitos. Os modelos de ligações analisados são compostos por ligações com parafusos passantes entre pilares metálicos preenchidos com concreto e vigas metálicas. A laje utilizada foi do tipo com fôrma de aço incorporada, com a utilização de conectores de cisalhamento para resistir aos esforços em conjunto com a viga. Para simular a situação de pilar intermediário, foram utilizados modelos com formato cruciforme, os quais foram submetidos à força cíclica reversível com a finalidade de submeter à estrutura a esforços semelhantes aos provocados por vento e sismo. Além do efeito da força cíclica, este trabalho avaliou também a influência na rigidez da ligação causada pela taxa de armadura da laje e pelo detalhe de ancoragem da armadura de continuidade ao pilar misto. Para isso foram ensaiados quatro modelos. Dentro da metodologia proposta, obteve-se numérica e experimentalmente, dados que permitiram a construção de curvas momento versus rotação e força versus deslocamento para a quantificação da rigidez e determinação da ductilidade da ligação. Como resultado das análises concluiu-se que a laje contribui mais na rigidez da ligação quando ela está submetida a momento fletor positivo e com relação ao método de ancoragem não houve diferença significativa nas rigidezes. This research studied the behavior of beam-column connection in composite steel-concrete structures and was developed with the use of numerical simulation and experimentation. The numerical simulation was performed using the program DIANA which is based on the finite element method. The models are composed of connections with bolts passing through the concrete filled tube (CFT) column and steel beams with a steel deck. It was used shear connectors for the slab works together with the beam to resist the bend. To simulate the situation of the middle column, they are used models with cruciform form, which were subjected to reversible cyclic loading in order to bring structure the efforts similar to those caused by wind and earthquake. Besides the effect of cyclic loading, this research also evaluated the influence on the connection stiffness caused by the slab reinforcement ratio and anchors detail to the column of some bars. To obtain this information four models were tested. Within the proposed methodology numerical and experimental data were obtained which made possible the construction of moment versus rotation curves and loading versus displacement for the quantification of stiffness and ductility of the connections. The result of this research shows that the slab contributes more on the increase of stiffness when the connection is subjected to sagging moment and about the method of anchoring, there is no significant difference on stiffness between the two methods.

Due to the large increase in the use of precast concrete structures in multistory buildings, this work covers a study on the behavior of beam-column connection with emphasis on the continuity provided by the slab reinforcement. Two prototypes were tested, each one with a different detail of the continuity reinforcement distribution. In both connections, the steel area used on the concrete cover of the hollow core slab was the same, varying the amount of bars that passed through the column and the ones that were placed adjacent to the column. The experimental results showed that the connection with bars adjacent to the column presented stiffness increase and a better cracking control. According to the classification the two tested connections can be considered semi-rigid. Em decorrência do grande aumento na utilização de estruturas pré-moldadas de concreto na construção de edifícios de múltiplos pavimentos, abordou-se neste trabalho o estudo do comportamento de ligações viga-pilar com ênfase na continuidade proporcionada pela armadura da laje. Dois protótipos foram ensaiados, cada um deles com um detalhamento diferente de distribuição da armadura de continuidade. Em ambas as ligações, a área de aço utilizada na capa da laje foi a mesma, variando a quantidade de barras que passavam através do pilar por meio de aberturas e as que se localizavam em suas laterais. Os resultados experimentais mostraram que a ligação com barras laterais ao pilar apresentaram aumento da rigidez e maior controle da fissuração. De acordo com a classificação realizada, as duas ligações ensaiadas podem ser consideradas semi-rígidas.

O uso de elementos de concreto pré-moldado impulsionou a industrialização da construção civil. No entanto, esta prática trouxe descontinuidades de esforços entre os elementos que compõem as edificações. Com isto, estudos relativos a tipos de ligação se tornaram frequentes em numerosos centros de pesquisa, com o objetivo de melhorar a continuidade entre os elementos estruturais, aumentando a rigidez e capacidade das ligações. Desta forma, este projeto aborda um estudo numérico do comportamento de uma ligação viga-pilar, parcialmente pré-moldada, com chumbadores de aço grauteados e barras de aço negativas para resistir ao momento fletor positivo e negativo, respectivamente. Esta estrutura se assemelha com a ligação de Tipologia 1 da NBR 9062 (ABNT, 2017), diferenciando-se no uso de concreto com fibras de aço nos consolos e nos dentes da viga. Primeiramente, para o presente estudo foi desenvolvido um modelo numérico com o auxílio do programa DIANA®, o qual é baseado no método dos elementos finitos (MEF), validando-o por meio dos resultados experimentais de pesquisa anterior como as curvas momento versus rotação, o padrão de fissuração e os modos de falha. Então, investigou-se diferentes parâmetros como a substituição do concreto com fibras de aço para concreto convencional, os diâmetros e posições dos chumbadores e a taxa das barras negativas. No estudo paramétrico foi simulado nove modelos no total. Substituindo o concreto com fibras de aço para o convencional não provocou diferenças significativas no comportamento da ligação. Aumentando a distância entre os chumbadores duplos, consequentemente diminuindo o efeito de grupo e aumentando o de borda, elevou-se a rigidez e a capacidade da ligação sob momentos positivos. Como esperado, o aumento nos diâmetros dos chumbadores elevaram a rigidez e a capacidade da ligação. Para todos os modelos solicitados por momento fletor positivo, o modo de falha com a plastificação do chumbador e o esmagamento do concreto não se modificou com nenhuma variação paramétrica. Como demonstrado em trabalhos anteriores, há um aumento na rigidez e na capacidade da ligação sob momentos negativos quando se aumenta a taxa das barras negativas. O modo de falha considerando a plastificação do aço para todos os modelos sob momento negativo não se alterou. Na sequência, um estudo teórico foi executado nos modelos com as variações da taxa de barras negativas. Todos os modelos foram classificados como ligações semirrígidas de acordo com o coeficiente (αR). Conclusões mostram que a formulação da NBR 9062 (ABNT, 2017) para prever a rigidez secante não é adequada para a ligação em estudo, quando comparada com a rigidez numérica. Isto é esperado devido às diferenças entre as ligações estudadas e a ligação de Tipologia 1. The use of precast concrete elements carried the industrialization of civil construction. However, this practice brought discontinuities of efforts between elements composing the buildings. Therefore, research concerning the study of types of connections became frequent in numerous research centers, aiming to improve the continuity between structural elements by increasing their stiffness and the connection capacity. Therefore, this project approaches a numeric study of the behavior of a beam-column connection with partially precast concrete with grouted steel dowels and negative steel bars to resist the positive and negative bending moments, respectively. This structure resembles the connection described in Typology 1 from NBR 9062 (ABNT, 2017), differentiating in the use of concrete with steel fibers in corbels and dapped end. Firstly, this study developed a numeric model employing software DIANA® based on finite element analysis (FEA), validating it through experiment testing results of previous research as curves of bending moment versus rotation, crack patterns, and failure modes. Then, it investigated different strategic parameters such as substituting concrete with steel fibers for conventional concrete, diameters and the position of dowels, and negative steel bars ratio. The parametric study simulated nine models. Replacing traditional concrete with concrete with steel fibers did not cause relevant differences in the connection behavior. Increasing the distance between the double dowels, which decreased the group effect and increased the edge effect, raised the stiffness and capacity of connection under positive moments. As expected, the increase in dowel diameters elevated the stiffness and the connection capacity. For all models under positive bending moments, the failure mode with dowel yielding and concrete crushing did not vary with any parameter variation. As demonstrated in previous works, there is an increase in both the stiffness and the connection capacity under negative moments when the negative steel bars ratio increases. The failure mode considering steel yielding for all models under negative moments did not change. A theoretical study was performed after the parametric study on the models with a rate of negative steel bars variations. All these models were classifieds as semi-rigid connections according to the coefficient (αR). Conclusions show that the NBR 9062 (ABNT, 2017) formulation to predict the stiffness of this connection is not accurate when comparing it with the numeric stiffness. This is expected due to differences between the studied connections and the Typology 1 connection.