In this work, the study of the evolutive behaviour of composite steel-concrete sections used in bridge decks was performed. A new method is proposed for the annex of EC3 part 2, in order to study the evolution effective steel area in a composite section, for serviceability and ultimate states. A coherent theoretical framework is presented, based on several relevant codes, namely the new Eurocodes. With this framework, a computer program is developed taking into account several important aspects in the behaviour of steel-concrete composite sections, such as nonlinear stress-strain relationships of the materials, local buckling of steel plates, time-dependent effects in concrete behaviour and load history. Also a new algorithm is proposed in order to compute strain fields at the section level from a known set of internal forces in the section, in nonlinear constitutive relations. Results obtained with the developed computer program are presented for several examples of typical sections found in bridge decks. Those results include moment-curvature plots, evolution of the strain field, evolution of the neutral axis, evolution of the stress in some points of the section. The influence of the concrete ultimate resistance and the staged construction sequence in the behaviour of the section is also evaluated.

This paper presents recent research, concerning some preliminary design guidelines to be applied in GFRP composite sandwich panels, for civil engineering applications. For more than a decade, the foundations of preliminary design of concrete, wood and steel structures, have been fully established in structural design codes and technical recommendations. Since FRP structures at the moment possess no standard design code, its preliminary design guidelines are nowhere to be found. This work pretends to fill this gap in knowledge, by providing simple and clear design guidelines to be applied in classical known GFRP composite sandwich panels, more specifically in home buildings. Just like in concrete structures, for GFRP structures one of the most unfavourable design state is the serviceability, mainly due to the long term deflection. Therefore, this long term deflection will be used to estimate the minimum span/height ratio necessary to “indirectly” verify the serviceability state. This is performed using an extensive parametric analysis: of the span beam model; type of materials; type of support; load levels; and geometrical properties. In this work in order to correctly estimate the flexural and shear deflection, the Carrera Unified Formulation is used, therefore no simplified shear correction factor is needed.

This paper presents a new hybrid double mixed stress (4f-HMS) model, for the static analysis of isotropic plane structures, in which it is assumed a physically and geometrically linear behaviour. The main improvement of this model is, it approximates independently the three most important fields in the domain, more specifically the strain field, the stress field and the displacement field of each element. The displacements along the static boundary, considered to include inter-element boundaries, are also directly approximated. For the approximation functions in the space domain, a complete set of orthonormal Legendre polynomials are used. The adoption of these functions enables the use of analytical closed form solutions, for the computation of all linear structural operators, and leads to the development of very effective p- refinement procedures. The model being discussed is tested in terms of convergence capabilities using classical elastic strain energy and other common variables, in which the monotonic convergence is tested. To validate the model and to illustrate its potential, several numerical examples are discussed and comparisons are made, with solutions obtained using analytical results and other known finite element formulations.