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Progressive collapse induced by fire and blast
No full textComprehensive finite element modelling of key elements is essential to improve the robustness assessment of structures subjected to a coupled effect of fire and blast. Focusing the attention on steel structures, a method for a realistic multi-hazard approach is presented. The problem has been investigated at the material level first and then at the structural level. The material level was studied performing a detailed experimental investigation in a wide range of strain rates and temperatures. A typical structural steel, namely S355, has been studied. A Split Hopkinson Tensile Bar equipped with a water-cooled induction heating system was used for the mechanical characterisation at high strain rates (300 1/s, 500 1/s and 850 1/s) and in a wide range of temperatures (20C, 200C, 400C, 550C, 700C and 900C). A Hydro-Pneumatic machine and a universal electromechanical testing machine were used for intermediate (5 1/s and 25 1/s) and quasi-static (0.001 1/s) strain rate tests at room temperature, respectively. Results showed that the S355 structural steel is strain rate sensitive, keeping its strain hardening capacity with increasing strain rates. The temperature effect was studied by means of the reduction factors for the main mechanical properties. Results at high strain rates highlighted also the blue brittleness phenomenon between 400C and 550C. The link between the material and the structural level is a material constitutive law able to take into account the strain rate sensitivity and the thermal softening. The widely used constitutive law proposed by Johnson and Cook was calibrated using the experimental results. A critical review of this material model highlighted a perceptible variation of the thermal softening parameter at different temperatures. Following a fitting approach, a modification of the dimensionless temperature (T*) has been proposed.The structural level was numerically investigated adopting the calibrated material model. Explicit non-linear dynamic analyses of a steel column under fire conditions and followed by an explosion were performed. The commercial code LS-DYNA was used. A method for a realistic multi-hazard approach has been proposed by studying the residual load bearing capacity. The results can be also of great interest to establish the initial conditions that could potentially lead to the onset of progressive collapse in steel framed structures under a combined effect of fire and blast. As expected, the results indicated that the load bearing capacity is influenced by the stand-off distance, the charge size as well as the column boundary conditions. The time of fire loading at which an explosion is triggered is a critical parameter as well
Characterization of natural stone material used in the Nordic eastern urban and costal environment
No full textThe report analyses the main properties pertaining to the durability of Finnish granitoid rocks, based upon extensive field and laboratory data collected during the past ten years. Commercial materials have been tested and compared along ten years of production and their frost resistance assessed according to European standards. Laboratory tests have been coupled with non-destructive methods most used on site assessment as ultra-pulse velocity and Schmidt hammer in order to compare the results of commercial materials with materials on construction site. Evaluation of durability has included petrographic analysis, crack density, and for site exposed material, chemical analysis, to understand the environmental effects on it. The material has generally maintained its original properties. It has natural heterogeneity, and it presents higher interlocked cracking network on the surface of the exposed materials. Site samples in some cases have shown chemical changes due to environmental actions
Development of a 300W 105/0.15 fiber pigtailed diode module for additive manufacturing applications
No full textThe paper reports on the design, manufacturing and preliminary characterization of a new compact and high beam quality laser diode multi-emitter module able to deliver about 300 W in a standard 105/125 fiber with 0.22 numerical aperture and 95% of power is in NA 0.15. The layout exploits a proprietary architecture and uses a plurality of 905 nm and 940 nm chips properly combined through spatial, polarization and wavelength multiplexing. Given its small footprint and low ownership costs, the module has been specifically devised as a direct diode laser source for small/mid size metal powder based additive manufacturing machines
Lean VOC-air mixtures catalytic treatment: cost-benefits analysis of competing technologies
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Il Social Housing a Torino come strumento di sviluppo economico e sociale: l'esempio di una residenza di Social Housing nel centro di Torino
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A scalable middleware-based infrastructure for energy management and visualization in city districts
No full textFollowing the Smart City views, citizens, policy makers and energy distribution companies need a reliable and scalable infrastructure to manage and analyse energy consumption data in a city district context. In order to move forward this view, a city district model is needed, which takes into account different data-sources such as Building Information Models, Geographic Information Systems and real-time information coming from heterogeneous devices in the district. The Internet of Things paradigm is creating new business opportunities for low-cost, low-power and high-performance devices. Nevertheless, because of the "smart devices" heterogeneity, in order to provide uniform access to their functionalities, an abstract point of view is needed. Therefore, we propose an distributed software infrastructure, exploiting service-oriented middleware and ontology solutions to cope with the management, simulation and visualization of district energy data
Einstein farà luce sull'universo oscuro
No full textSi riassume lo stato dell'arte riguardo a materia oscura ed energia oscura nell'universo. Si propone un esperimento per verificare l'effetto del momento angolare dell'alone di materia oscura in cui si ritiene sia immersa la nostra galassia, appoggiandosi ai punti lagrangiani del sistema terra-sole