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Performance-based engineering (PBE) methodologies allow for the design of more reliable earthquakeresistant structures. Nonetheless, to implement PBE techniques, accurate finite element models of critical components are needed. With these objectives in mind, initially, we describe an experimental study on the seismic behaviour of both beam-to-column (BTC) and column-base (CB) joints made of high-strength steel S590 circular columns filled with concrete. These joints belonged to moment-resisting frames (MRFs) that constituted the lateral-force-resisting system of an office building. BTC joints were conceived as rigid and of partial strength, whereas CB joints were designed as rigid and of full strength. Tests on a BTC joint composed of an S275 steel composite beam and high-strength steel concrete-filled tubes were carried out. Moreover, two seismic CB joints were tested with stiffeners welded to the base plate and anchor bolts embedded in the concrete foundation as well as where part of a column was embedded in the foundation with no stiffeners. A test programme was carried out with the aim of characterising these joints under monotonic, cyclic and random loads. Experimental results are presented by means of both force-interstory drift ratio and moment-rotation relationships. The outcomes demonstrated the adequacy of these joints to be used for MRFs of medium ductility class located in zones of moderate seismic hazard. Then, a numerical calibration of the whole joint subassemblies was successfully accomplished. Finally, non-linear time-history analyses performed on 2D MRFs provided useful information on the seismic behaviour of relevant MRFs. Copyright plastic hinge located on the column outside the plinth detected by computing the difference between I-1 and I-0 (Figure 8(c) and (d)). Collapse was caused by brittle failure of the column wall near the weld between the column and the base plate owing to phenomenon of local instability in the wall of the column, as depicted in Figure 12(d). In this case, plastic rotations exceeded 45 mrad. Finally, with reference to CB joints, no requirements of a minimum plastic rotation are provided in EN1998-1 [23]. Figure 11. Force-interstorey drift ratio curves and moment-rotation relationships: (a) CBJSEE, (b) CBJSER, (c) CBJINE and (d) CBJINR.

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Background: Prompted by the EN 1090 standard, an important evolution has been observed in recent years about steel structures execution. Laser cutting is appealing for high machining speed and precision in implementation of details with complex geometry, but requires consideration for the effects of the inherent thermal process. Objective: The present study investigates the correlations between material properties altered by the laser cutting process and behaviour of the material and of structural joints subjected to high-cycle fatigue. Method: High-cycle fatigue tests on material samples and on structural bolted connections were carried out in order to correlate the structural response with material properties. For this purpose, hardness and residual stresses were analysed in depth, from the cutting surface inward and specimens processed using different laser cutting parameters and post-annealing treatments were investigated. Results: High-cycle fatigue tests on material samples and on structural bolted connections, processed by laser cutting, show a favourable fatigue behaviour of S460N steel, despite the high values of hardness on cut surface, in agreement with Eurocode 3 fatigue category FAT160 and FAT90, respectively for base material and drilled holes. Conclusion: Structural bolted connections made of S460N steel cut by laser exhibit a favourable fatigue behaviour. Local hardness is an important indicator, favourably complemented by the residual stress distribution to understand the effects of laser cutting and correlate them with the high-cycle fatigue behaviour.

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Computer Numerical Controlled (CNC) laser cutting tools are developing as an alternative to conventional cutting systems thanks to increased accuracy, non-contact processing, higher productivity, less energy demand. An IR camera is utilized to monitor the laser cutting process of a steel plate. Even though the process is very complicated an analytical solution of the temperature field generated on a slab by a point source moving along one direction of the plate surface is provided in order to interpret the temperature field experimentally obtained by the IR camera.

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