177,535 research outputs found
FRC Bending Behaviour: a Damage Model for High Temperature
No full textWORKSHOP ORGANIZED BY THE FIB TASK GROUP 4.3, P.G. Gambarova, R. Felicetti, A. Meda and P. Riva (Eds.
Sistema per il miglioramento della capacità di isolamento termico di lastre o pannelli per la protezione al fuoco
No full textSYSTEM FOR IMPROVING THE THERMAL INSULATION CAPACITY OF COATING ELEMENTS FOR FIRE PROTECTION
No full textA system for improving the thermal insulation capacity of coating elements for fire protection comprising: a coating element (10) for the protection against fire; a structure (11) to be protected from the fire, such as an attic, a beam, or a wall; said coating element (10) is placed at a pre-set distance from said structure (11) to form an empty gap (12) between said coating element (10) and said structure (11); an intumescent paint (13) is applied onto the internal surface of said coating element (10)
Residual behavior of steel rebars and R/C sections after a fire
No full textThe mechanical properties of various steel bars exposed to high temperature ("residual" properties) are experimentally investigated up to 850 °C, with reference to a number of steel and bar types (carbon and stainless steel; quenched and self-tempered bars; hot-rolled and cold-worked bars; smooth and deformed bars). The aim is to clarify to what extent the thermal sensitivity of the different bars affects the ultimate capacity of a typical R/C section subjected to an eccentric axial force, past a fire ("residual" capacity). As usual in the design of R/C sections under combined bending and axial loading, the ultimate behavior is represented through the "M-N envelopes", where the materials strength decay due to high temperature is taken into account. The results show that quenched and self-tempered bars (QST), very popular in Europe, are more temperature-sensitive above 600 °C than the carbon-steel bars extensively used in the States and nowadays rarely used in Europe. Furthermore, the best response is exhibited by the stainless-steel bars, provided that they are hot rolled, as it is generally the case for medium- and large-diameter bars. Similar conclusions can be drawn for the sections reinforced with the different bar types. 2009 Elsevier Ltd. All rights reserved
Le prove penetrometriche per la stima della risposta meccanica delle malte nelle murature degli edifici.
No full textA penetration test to study the mechanical response of mortar in ancient masonrty buildings
No full textPulse-Echo Monitoring of Concrete Damage and Spalling during Fire
No full textMonitoring concrete damage and spalling progression in structural members during fire tests (hot conditions) is a central but challenging task, since the high temperatures involved make difficult the implementation of most of the common Non-
Destructive evaluation methods. Hence, an advanced ultrasonic technique – Ultrasonic Pulse-Echo (UPE) – was recently adapted for real time survey in fire test, in order to evaluate the material damage during heating. The UPE technique was implemented at the cold (upper) face of concrete slabs (800x800x100 mm) heated at the bottom face according to the Standard Fire and subjected to biaxial compressive membrane loading. Different concretes were tested, with grades ranging from 40 to 60 MPa, with and without different kinds of fibre (monofilament or fibrillated polypropylene, or steel fibres). Furthermore, different load levels were applied, from 0 to 25% of the original compressive strength. During tests, spalling was generally observed in loaded plain concrete (up to 50-60 mm depth), while only slight scaling was experienced on
unloaded samples or if polypropylene fibre was added. The method proved to be very effective in recognizing the decay of the Ultrasonic Pulse Velocity (UPV) with temperature and the role played by external loading and fibre type
Strutture in acciaio esposte al fuoco: analisi meccanica e verifiche di resistenza
No full textLe strutture in acciaio sono generalmente sensibili agli effetti di un incendio a causa dell’elevata conducibilità del materiale e delle ridotte sezioni trasversali degli elementi, entrambi fattori che comportano un repentino aumento della temperatura. Una volta raggiunta la temperatura di 600°C, le proprietà meccaniche dell’acciaio risultano più che dimezzate rispetto le condizioni ordinarie. Tramite l’opportuna progettazione del sistema strutturale e di protezione è tuttavia possibile ottenere un adeguato comportamento strutturale in caso d’incendio. Tale fase di progettazione deve basarsi su un attento studio ingegneristico che, partendo da una corretta analisi del comportamento meccanico, porti alle opportune verifiche di resistenza tenendo in conto effetti rilevanti quali le azioni indirette dovute alle dilatazioni termiche impedite e il contributo dell’iperstaticità. Nel presente articolo vengono presentati gli aspetti principali dell’analisi meccanica e delle verifiche da effettuare per una struttura in acciaio esposta al fuoco
Explosive spalling in R/C structures exposed to fire: key aspects in experimental testing
No full textExplosive spalling in R/C members exposed to fire consists in the violent expulsion of the hottest layers of concrete, due to the combination of compressive stress and vapour pressure, with the consequent reduction of the bearing cross-section and of the structural fire resistance. Experimental tests aimed at assessing concrete spalling sensitivity can be performed at dif-ferent scales, namely small, intermediate and real scale, with increasing time and cost of testing. The correct level of investi-gation must be defined as the right compromise between efficiency and representativeness of the real case. Starting from the comparison among different test setups at different scales, the main parameters to be considered in planning the experi-mental investigations will be described. On the other hand, with regards to the definition of the mix design, it will be shown how the use of different types of fibre can bring remarkable benefits against spalling
Experimental Methods for Spalling Monitoring During and After a Fire
No full textMonitoring the progress of spalling and moisture front in concrete elements subjected to heating is a challenging task, since most of the available techniques can be hardly implemented in the test furnace. This is a critical issue, because the measurement of temperature and pressure can be not sufficient to define the conditions for spalling if depth and area involved, as well as occurrence time are not known. Generally speaking, monitoring can be performed by means of Real-Time or Post-Event survey. As concerns the former approach, promising results are expected to come from ultrasonic Pulse-Echo and Ground-Penetrating Radar methods, both based on the measurement of the time delay of (ultrasonic and electromagnetic, respectively) echoes reflected by the specimen side exposed to fire. Other methods for Real-Time monitoring can be Digital Image Processing of pictures taken during heating, and Acoustic Emission. As regards spalling survey after fire, laser profilometry, optical size measurement and weighing of the collected splinters can be co-ordinately used to depict some statistical trends of the fracture process due to fire. These methods (except Acoustic Emission) have been – or will be – implemented in the case of fire tests performed on concrete slabs subjected to heating at the bottom face, and the results are discussed in the present paper
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