This research deals with the axial-bending interaction in bolted steel beam to column connections along the strong axis of the column. In order to define the interaction curves, firstly, a series of tests of doubly symmetric bolted connections were carriedout in which two column sizes were considered, while the beam, end plate and bolts remained the same. These joints were tested under pure compression, as well as simultaneous bending and compression, and with different load levels. Afterwards, reduced finite element models including initial imperfections were made. These models are validated by means of the results obtained in the experimental program. The aim of the reduced model is to enlarge the range of studied loading combina-tions in terms of different percentages of axial load and bending moment. Finally, with the results obtained, a preliminary normalized interaction diagram for this type of joints wasdeduced.

The aim of this research is to provide an alternative for the conventional design of beam-to-column connections in building structures. The new design is performed by means of Structural Topological Optimization and executed by means of additive manufacturing with steel. Regarding the methodology, the joint that would be manufactured by conventional methods (i.e. welded and bolted plates) is modelled by means of finite elements in the first place. Its behavior is obtained, as well as the boundary conditions and the loads to be applied to the part that is going to be optimized. Subsequently, a solid part is defined and optimized by means of the optimization module TOSCA. Then, the complete joint is simulated with the optimized connection, and the behavior and the weight of the material used are compared with those of the conventional joint.Some modifications are made to improve some aspects of the design. Afterwards, the optimized joint is printed with steel S316L, the connection is as-sembled with the columns and beams, and it is tested. The experimental results are analyzed to be able to make the necessary adjustments both in the connection and in the design methodology.

A study of axial¿moment interactions of bolted connections with double extended end plates is presented in this paper. Six connections, subjected to pure compression and flexural compression were tested for this purpose. After the experimental campaign, finite element models were developed and calibrated to accurately reproduce the experimental results. The models included initial imperfections to capture the possible buckling failure modes in the column web and the beam flanges. Moreover, the models with and without initial imperfections were compared for different sizes of the imperfection. Finally, the results obtained from the experimental and the computational models provided sufficient and adequate information to construct an axial-moment interaction curve for the tested joints.

Torsional effects in joints need to be investigated in order to get a complete model of the joint and also to assess the real boundary conditions for the lateral torsional effects in the beams of structural frames. Phenomena such as: torsion, warping, lateral buckling, etc. are usually analysed assuming simplified boundary conditions, namely pinned or rigid, in frame analysis which can lead to erroneous and non-conservative results. With the aim of knowing the correct boundary conditions and real behaviour of the joints under torsion, an experimental program is carried out consisting of two tests of mayor axis doubled extended bolted end plate joints subjected to torsion about the axis along the length of the beam. These experimental results have allowed the validation of the finite element models carried out using the program Abaqus. Once the models are validated models, a parametric study is performed to assess the stiffness and resistance. This study also verifies that these joints behave in a semi-rigid way when compared with the torsional characteristics of the attached beam. Besides, the beam fails prior to the connection in most cases, and therefore, the joints can be assumed to behave as full-strength. Analytical expressions are proposed and checked with the FEM results proving that the proposed analytical formulae and the proposed mechanical model can predict the stiffness quite accurately, with an average error of 8.5%. Despite these joints can be classified as full-strength under torsion, an assessment of their resistance is done as well.

Dimensioning the stairs in case of fire is amongst the most important features in today architecture design. A bigger complexity of the buildings (mixed uses, crowded spaces, occupants with disabilities, tall structures, etc.) is added to new social habits, and the activities traditionally placed on the lowest parts of the buildings tend to occupy the upper floors. This article shows that the prescriptive calculations for the dimensioning of protected stairs are unable to face this challenge because they are based on simplified models, only valid for conventional buildings and distributions. It analizes the Spanish Technical Building Code, showing its weakness, and introduces the necessary performance-based design concepts to understand the problem. It concludes that any complex design must be addressed studying the real movement o f the occupants, that can be modelled with the use of computational tools.

Beam to column connections subjected to loads in the beam minor axis direction are usually considered either as pinned or rigid for both resistance and stiffness checks. However, modern codes contemplate the possibility of semi-rigid and partial strength connections. The Eurocode 3 provides criteria, based on the component method, to characterise such connections. There are unresolved issues regarding three-dimensional connections and connections subjected to out-of-plane effects that need further research. Their behaviour relies mainly on the characterisation of the components acting on the T-stub under out-of-plane bending, and this characterisation is the aim of this paper. An experimental program consisting of five T-stub tests has been carried out and finite element models have been developed. The finite element models have been validated with the experimental results and prove to be an accurate tool for the characterisation of 3D connections. The connection characteristics have been obtained by means of tests and finite element models, and after comparison with the limits provided by the Eurocode 3, it is concluded that all connections under study are indeed semi-rigid and partial strength.

Beam to column connections subjected to loads in the beam minor axis direction are usually considered either as pinned or rigid for both resistance and stiffness checks. This simplification is also assumed at the time of considering the stability of the column and the lateral buckling of the beams. However, as proven in the companion paper by means of laboratory tests and numerical simulations, these types of connections are actually semi-rigid and partial strength. The consideration of their real semi-rigid behavior can lead to a more accurate global analysis and, consequently, more optimized structures. Their behavior relies mainly on the characterization of the components acting on the T-stub under out-of-plane bending. In this paper a parametric analysis is performed to define the components involved. Analytical expressions are specified to describe each one of the components and the assembly process following a proposed mechanical model. The stiffness and strength that are obtained compare very satisfactorily with the experimental results of the T-stubs described in the companion paper.