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Dynamic analysis of composite beam and floors with deformable connection using plate, bar and interface elements.
(2019) Machado, Wanderson Gonçalves; Silva, Amilton Rodrigues da; Neves, Francisco de Assis das
New architectural tendencies combined with more resistant materials and increasingly efficient structural systems, results in projects that are safe for ultimate load capacity, but with problems related to service loads, i.e., the structure doesn’t collapse, but causes discomfort to the user. Structures with deformable connection are formed by the association of two or more structural elements by means of a deformable shear connection. In construction the most common cases of this type of structures are steel-concrete composite structures. Among these, the composite beams and floors are more susceptible to be excited by dynamic loading induced by human rhythmic activities, as walking, dancing, jumping, among others. The objective of this work is, from the three dynamic finite element formulation (plate, bar and interface), to show the efficiency of these in simulation of composite floors and beams with deformable connection under dynamic loading, where the deformable shear connection is simulated by the interface element, being the main contribution of this work. The proposed analysis model is tested and validated by means of frequency analysis results and natural vibration modes of composite floors and beams, as well as the calculation of displacements and accelerations of those when subjected to dynamic loads due the rhythmic activities. Another contribution of the model proposed in this article is the verification of the influence of the “shear lag” effect in the determination of the natural frequencies and vibration modes of composite beams, which cannot be evaluated when analyzed only for bar and interface elements.
A numerical model for concrete slabs under fire conditions.
(2013) Caldas, Rodrigo Barreto; Fakury, Ricardo Hallal; Sousa Junior, João Batista Marques de; Pitanqueira, Roque Luiz da Silva
A numerical model for the behavior of concrete slabs in a fire is described. This model consists of a shell finite element, a damage constitutive model for concrete with steel reinforcement and the consideration of heat transfer through the thickness of the slab. An improved damage constitutive model for concrete at elevated temperatures has been implemented considering compressive and tensile behavior through an orthotropic compliance theory. The damage in compression is based on the concrete stress–strain relationships presented by the European Committee for Standardization. Several calculations have been performed to validate the improved model. The comparison with experimental tests and numerical results confirm the validity of the approach for reinforced concrete slabs subjected to large transverse displacement.
Finite element implementation for the analysis of 3D steel and composite frames subjected to fire.
(2014) Caldas, Rodrigo Barreto; Fakury, Ricardo Hallal; Sousa Junior, João Batista Marques de
This paper presents a finite element formulation for the numerical analysis of three-dimensional framed steel, reinforced concrete or composite steel and concrete structures subjected to fire. Several specialized and commercial programs may be used for the analysis of structures in fire condition. Within this context, the purpose of this work is to present the steps taken to extend a previously developed static analysis procedure with beam elements in order to cope with the thermal and structural analysis of structures under fire action. Physical nonlinearity and material propertydegradation considering the temperature distribution are taken into account at the cross section level, which is divided into quadrilateral or triangular finite elements. Thermal strains are considered through the effective strain concept, and the resulting nonlinear system of equations is solved by the Newton-Raphson scheme. The accuracy and capability of the formulation to simulate the behavior of framed structures under fire action are assessed through comparison with various numerical and experimental results.

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