Numerical formulation for advanced analysis of semi-rigid steel-concrete composite frames

Resumo

The present work aims at the implementation and validation of a displacement-based two-dimensional
numerical formulation including several sources of non-linearities in steel-concrete composite frames, such as
second-order effects, plasticity and beam-to-column semi-rigid connections. The co-rotational-based approach
is used to describe the finite element formulation, allowing large displacements and rotations in the numerical
model. Rotational pseudo-springs are used at the ends of the finite element, where the gradual loss of stiffness
is determined by combining the normal force and bending moment (NM) in the cross-section. The limiting of
the uncracked, elastic and plastic regimes are defined in the NM diagram. In the cross-sectional analysis, the
Strain Compatibility Method (SCM) is used to capture the axial strains in the section components. In this way, the
constitutive models of the materials are described by continuous functions. The semi-rigid connections are also
simulated by the rotational pseudo-springs at the finite elements ends, and the connection behavior is given by
its moment-rotation relationship. A multi-linear model for beam-to-column connections is used. To validate the
proposed numerical formulation, the results obtained are compared with numerical and experimental data available
in the literature. Since the model proposed here starts with the concentrated simulation of nonlinear effects, an
examination of the finite element mesh refinement is also carried out.