Iskanje po repozitoriju

A+ | A- | | SLO | ENG

Povzetek: Performance-based structural fire design relies on models that capture material and structural behaviour during heating and cooling. Such models require experimental data, but experiments are often time- and resource- intensive. Optimal Experimental Design (OED) can reduce the number of tests needed by minimizing the variance of parameter estimates. This study demonstrates the use of OED, using D-optimality as the optimization criterion, for an experimental setup that measures the thermal elongation of concrete specimens. In these tests, cylindrical concrete specimens are slowly heated to a predefined maximum temperature while their elongation is being measured. The goal of the experimental campaign is to calibrate a model for the free thermal strain of concrete during cooling. The OED determines the optimal exposure that is expected to result in the lowest variance around the mean values of the parameter estimates. The results of the OED are compared with a baseline experimental design without optimization, showing that the advantages of OED become increasingly evident as the number of experimental runs grows and intuitive reasoning becomes less reliable. In addition, the approach is validated considering real experimental data.
Ključne besede: optimal experimental design, concrete, thermal strain, cooling
Objavljeno v DiRROS: 08.04.2026; Ogledov: 200; Prenosov: 41
Celotno besedilo (1,10 MB)
Gradivo ima več datotek! Več...

Povzetek: Bench-scale fire testing has gained popularity as a highly controllable and cost-effective solution, overcoming many of the shortcomings of traditional large-scale fire resistance tests. Whereas gas-fired radiant panels have demonstrated significant success in this area, the present study introduces a novel High-Intensity Fast-Response Electric radiant Panel (HIFREP). Utilizing electrically operated radiation emitters, it provides more precise and quasi-instantaneous control over the thermal boundary conditions. HIFREP delivers high and stable heat fluxes up to 105 kW/m2 , and, due to the low thermal inertia of the emitters, can rapidly adjust its output to changes in the input. In this regard, the time constant of the emitters has been found to be less than 1 s, both during heating and cooling. It eliminates gas combustion and hence avoids the need for extraction hoods when testing the fire performance of non-combustible materials, making it suitable for traditional structural testing laboratories. The presented High-Intensity Fast-Response Electric radiant Panel also provides a reliable tool for the validation of FEM simulation results by accurately replicating the thermal boundary conditions in structural fire engineering analyses.
Ključne besede: radiant panel, fire testing, heat transfer, radiation, heat flux, thermal boundary conditions
Objavljeno v DiRROS: 16.06.2025; Ogledov: 858; Prenosov: 441
Celotno besedilo (1,98 MB)
Gradivo ima več datotek! Več...

Povzetek: In this study, the effects of natural fire exposure on the post-fire behavior of concrete beams are investigated. The study is based on laboratory tests where three reinforced concrete beams were subjected to fire exposure using an electric radiant panel. This panel enables a precise application of radiative heat exposure closely mimicking natural fire exposure in a safe manner. During the test, the deflections, deformations and temperature changes are measured for all three concrete beams. Additionally, finite element modeling (FEM) is applied to supplement these tests, demonstrating the performance of existing structural fire engineering calculation tools in evaluating the burnout performance of concrete beams. The results of the tests show that the electric radiant panel provide a novel approach for fire simulation which is effective in replicating natural fire conditions, by applying the heat flux as specified in the Eurocode Parametric Fire Curve in a highly controlled manner. The uniformity of the temperature field measured inside the beams and the consistent deformations observed during the heat exposure across all three tests underscores the accuracy of the fire simulation. Furthermore, post-fire assessments reveal that while the exposed beams suffered some reduction in load-bearing capacity, they retained a significant portion of their original strength that was consistent across all three beams. The numerical simulations conducted in this study demonstrate a high level of accuracy in predicting the behavior of the concrete beams during fire exposure. These simulations effectively mirrored the experimental results, validating that they are a valuable tool for assessing concrete structures' performance in fire scenarios.
Ključne besede: concrete beam, fire testing, numerical modeling, radiant panel
Objavljeno v DiRROS: 28.11.2024; Ogledov: 1125; Prenosov: 629
Celotno besedilo (1,80 MB)
Gradivo ima več datotek! Več...

Povzetek: A commonly used approach to represent the thermal load in a compartment fire is the Eurocode Parametric Fire Curve (EPFC), which specifies gas temperatures (or rather adiabatic surface temperatures). Recognizing the significant deviations between real fires and the EPFC framework, the concept of model uncertainty is explored. This study does not aim to assess or improve the EPFC, but introduces a model uncertainty, allowing for reliability-based structural fire engineering (SFE). It presents a stochastic correction factor for the fire load density, based on the maximum temperature in steel sections. The focus is on the fire load density, but in general other parameters can be jointly taken into account as well. This correction factor considers protected and un- protected sections, incorporating variations in section factor and protection thickness. The findings reveal that the fire load density within the EPFC framework can be modified to better represent the severity of fire ex- periments. This approach ensures physical consistency of the obtained compartment gas temperatures, as opposed to alternative approaches for addressing the EPFC model uncertainty. While promising results are evident in this proof of concept, exploration for other types of structural elements and evaluation for structural systems is necessary before integration into design practices.
Ključne besede: structural fire engineering, compartment fires, fire load density, steel structures, reliability, probability of failure
Objavljeno v DiRROS: 17.04.2024; Ogledov: 1753; Prenosov: 473
Celotno besedilo (1,16 MB)
Gradivo ima več datotek! Več...