Metodología práctica para el diseño de pórticos de estructura mixta con uniones semi-rígidas

Résumé

Composite structures are based on an optimal use of the mechanical characteristics of both materials that compose them: steel and concrete. Despite of their many advantages, especially when combined with semi-rigid joints, their use in building is not very common. The use of these systems on a daily basis requires that new design methods and useful tools for semi-rigid composite joints to be studied. This investigation proposes analysis methods for composite structures with semi-rigid connections, the starting point being the required stiffness that leads to a better bending moment distribution. Together with the simplified joint design method also proposed herein, the number of necessary iterations to define a structure is reduced and, at the same time, an optimization is obtained. With the aim of achieving a more exhaustive knowledge of the semi-rigid composite joint behaviour several full-scale tests are carried out. These tests introduce an innovation with respect with the conventional configuration which consists of inserting the central reinforcement bars through the column flanges in order to improve the behaviour. Subsequently, finite element models are carried out which are validated with the experimental results until reliable models are achieved. These models are used to compare the performance of the conventional joints with the proposed alternative design. The proposed design for internal joints shows improved behaviour, which is more acute as the moments on each side of the joint become increasingly unbalanced. Regarding external joints, the same values are obtained as with the conventional design but without the need for a cantilever. A parametric study is also carried out on external and internal joints following the alternative design in order to define the components which intervene in it and to develop the corresponding analytical model by adapting the component method to the proposed joint characteristics. These modifications make the prediction of the joint characteristics match the real behaviour with good accuracy.