Name: Mateus Zimmer Dietrich
Type: MSc dissertation
Publication date: 31/03/2017
Advisor:

Namesort descending Role
Adenilcia Fernanda Grobério Calenzani Advisor *

Examining board:

Namesort descending Role
Adenilcia Fernanda Grobério Calenzani Advisor *
Ana Lydia Reis de Castro e Silva External Examiner *
Ricardo Hallal Fakury Co advisor *
Walnório Graça Ferreira Internal Examiner *

Summary: In continuous and semi-continuous composite beams, in hogging moment region, the bottom flange of the steel profile is compressed, if the web is not rigid enough to avoid lateral flexion, it will distort, implying a lateral displacement and a rotation of the compressed flange, characterizing a mode of instability called lateral-distortional buckling. The procedure of ABNT NBR 8800:2008 to verify this ultimate limit state
uses the elastic critical moment equation, by Roik et al. (1990), which is based on an inverted "U" mechanism, formed by two or more adjacent steel beams and the concrete slab on which they are attached. The composite beam rotational stiffness is the fundamental property for determining the elastic critical moment to lateraldistortional buckling. In simplified form, the rotational stiffness of the composite beam is defined as a series association of springs representing the rotational stiffness of
the concrete slab, the steel profile web and the shear connection. In this research, numerical models are implemented, using the finite element method, to evaluate the procedure of ABNT NBR 8800:2008 to determine the rotational stiffness of steelconcrete composite beams. The numerical models portray edge and internal composite beams to the floor with reinforced concrete slabs, shear connection with one or two welded shear connectors in the cross section and non-stiffened steel
profile web. The contributions of the insulated rigidities of the slab, the shear connection and the steel profile web to the composite beam rotational stiffness value are evaluated. The moment rotation curve of the concrete slab and its influence on the composite beam rotational stiffness is also investigated. As main conclusions, they can be cited: the ABNT NBR 8800:2008 formulation adequately predicts the web rotational stiffness; the rotational stiffness of the shear connection can be neglected in the calculation of the composite beam rotational stiffness, as recommended by ABNT NBR 8800:2008; the ABNT NBR 8800:2008 formulation for the calculation of slab rotational stiffness can be used for edge and internal composite beams, but it is recommended to adopt a coefficient equal to 1.71 for edge composite beam and 3 for internal composite beam, independent of the number of beams that make up the floor, and; in certain situations, the rotational stiffness of
the composite beam can be simplified as a portion of the web rotational stiffness.

Keywords: Steel-concrete Composite Beams, Lateral-distortional Buckling, Rotational Stiffness.

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