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The introduction of rib stiffeners in the extended end-plate joints can guarantee a beneficial increase of both the strength and ductility of the connection. Indeed, the presence of the rib influences the yield line distribution in the tensile zone of the connection, the depth of internal lever arm as well as the resistance of compression components of the joint . However, unexpected phenomena can develop if the stiffeners are not properly aligned with the beam web. Therefore, in this work, a parametric finite element (FE) analyses was conducted to investigate the influence of the rib constructional imperfection on both the local and global joint response. In particular, the variation of the compression center position and the development of additional internal actions in the bolt rows was monitored for five different rib misalignments. The results show that some geometrical imperfections could have a beneficial effect on the joint capacity limiting the beam out-of-plane mechanism when the plastic hinge develops at the beam extremity. © SDSS 2019 - International Colloquium on Stability and Ductility of Steel Structures.

Seismic design regulations rely on certain factors to reduce the earthquake actions due to inherent ductility and overstrength of the lateral force resisting systems. The behaviour factors given in Eurocodes are one such example, which when applied during the design process will ensure the life safety performance level of a building. Light-Weight Steel (LWS) structures fabricated with Cold Formed Steel (CFS) profiles are increasingly widespread in earthquake prone regions, however the current in practice edition of Eurocodes fails to acknowledge their seismic performance by not providing behaviour factors for them. The study presented herein addresses this issue by evaluating behaviour factor for the two commonly used LWS systems: CFS strap braced walls and CFS shear walls with gypsum board sheathing through FEMA P695 methodology. For each type of system, a set of archetypes, which represent a range of design parameters and building configurations are designed following the capacity design approach and their response is idealized by nonlinear numerical models. The performance of archetype models is evaluated systematically through the static pushover and the incremental dynamic analysis under a suite of forty-four normalized and scaled earthquake records, representing the probable seismic hazard to the buildings. Finally, by calculating the collapse probability while also considering the uncertainties from various sources, the suitability of a trial value of the behaviour factor used in the design phase of archetypes is evaluated. Based on the results, it is concluded that a behaviour factor of 2.5 and 2.0 for CFS strap braced walls and CFS shear walls with gypsum board sheathing is appropriate.

Cold-formed steel (CFS) members in buildings are in use for decades, but their earthquake performance remained unexplored, until recently. Eurocodes, which provide common approach for the design of buildings in Europe still lack the information on seismic design of CFS structures. However, for the last few years, University of Naples “Federico II” CFS research group is dedicated in investigating their seismic performance. One of the focus areas is characterizing seismic behaviour of CFS strap braced stud walls. This paper presents a generalized approach adopted in simulating hysteretic behaviour of these walls under cyclic load in OpenSees software. Numerical models are developed and calibrated on the basis of available experimental results.

This book is the 2015-2017 report of the RINTC project, which has been a joint project of ReLUIS and EUCENTRE. The project intended to assess the seismic risk of code conforming structures in Italy. The results presented herein are, in some cases, different from those presented in the previous years and from preliminary literature derived from this project. This is because, as discussed in the body of text, hypotheses and choices have been continuously revised until consolidation; this process might be continuing even after the end of the project. In general, all computed annual structural failure rates closely reflect specific assumptions on design, modeling and analysis of the considered structures, and this has to be always taken into account when discussing the results of this project. The working group of the project (listed below) consists of the following six sub-groups, each of which explores (i) seismic risk assessment of code-conforming structures, designs, modelling, and analyses of (ii) masonry buildings, (iii) precast reinforced concrete buildings, (iv) reinforced concrete buildings, (v) steel buildings, and (vi) base-isolated reinforced concrete buildings. The book is structured such that each chapter presents the research results from the corresponding sub-group: Chapter (i) introduces the objectives and framework of the project; Chapters (ii) ? (vi) develop code-conforming designs, modelling and analyses of buildings for each structural type; Chapter (vii) concludes the study presenting the final results of the computed failure rates for the structures examined in the preceding chapters. Moreover, readers can refer to Appendices A to C for the details of the considerations on (a) usability-preventing limit state, (b) soil-structure interaction, and (c) model-uncertainty, respectively.

The structural behaviour of steel moment resisting frames (MRFs) is strongly dependent on the beam-to-column joint behaviour. The role of the joints is crucial especially under accidental natural and human induced actions, as in the cases of earthquake and fire scenarios, which can occur subsequently after severe seismic events in urban areas. The study summarized in this paper aims at investigating the fire behaviour of seismically designed extended stiffened end-plate joint by means of finite element analyses (FEAs). The joint performance was investigated considering two scenarios: (i) in the first case the assemblies were subjected only to the fire action; (ii) in the second scenario the fire actions were applied to seismically damaged joints. The numerical results show that the fire action changes the restraining capacity of the joint, and local failure can also occur, especially when fire occurs after severe seismic damage.