SUMMARY OF PhD THESIS:
COMPOSITE COLUMNS UNDER AXIAL COMPRESSION AND BI-AXIAL BENDING MOMENTS
This research approaches the study of composite columns consisting of metal profiles coated with reinforced concrete, under the effects of axial compression and bi-axial bending moments applying a design procedure included in the “General Method” in Eurocode 4.
This PhD Thesis’ main interest is based on the approach to a structural element with both a rather complex analysis of its behavior and an increasing application in building structures, especially in tall buildings.
Identification of numerous variables affecting them has been made from a thorough review in bibliography. Approach of departing assumptions and design methods has been raised and developed following the specific legislation.
In terms of procedure, composite supports analysis began studying its section behavior, continued studying the bar as an isolated element and ended with an analysis of the entire structure.
When evaluating the section’s bearing capacity, characteristics of the materials which constitute it have been taking into account by considering the constitutive relations for concrete and steel. Regarding the bar behavior, its length influence has been analyzed in addition to its initial imperfection or eccentricities when applying the loads. As for the whole structure, lack of bracing has been the main topic studied. When designing isolated bars or the whole structure, second order effects, both geometric and mechanical, have been considered. 
After this theoretical study and due to the high computational complexity arising from not only the coexistence of materials with different behaviors but also the numerous variables taken into account, it was decided to develop a software which permits the user studying composite sections under the effects of axial compression and bi-axial bending moments. This module has been integrated into a more general software where nonlinear analysis of structures can be studied.
This work’s main contributions are:
* Obtaining the interaction diagrams of usual composite sections under axial compression and bi-axial bending, facilitating their sizing.
* Quantification of the influence of the rheological effects of concrete on the bearing capacity of composite columns.
* Development of a set of graphs for composite columns considering different bar lengths and different eccentricities when applying the load. As a result corresponding mechanical areas have been obtained.
* Evaluation of the effect which translationality (considered on different types of structures designed with composite columns) has on deformations and efforts. 
Thus, a new software for designing composite columns under a non-linear behavior has been developed, turning into a powerful tool for further research and making easier the design of this kind of three-dimensional structures.