Fire Technology最新文献

A simple design method typically applies a Fire Resistance Rating (FRR) to structural components in isolation based on their performance in the fire test. This approach naturally assumes that the interaction between these components does not degrade their fire performance. To assess the reliability of this assumption, this paper numerically investigated the fire performance of continuous steel columns, incorporating the effects coming from connected steel beams and composite slabs. A 3-step numerical validation, using ABAQUS and following a recommended general simulation process, confirmed the numerical model's accuracy for this research through agreement with experimental tests. The simulation results founded that the well-designed interior column subassemblage, T4-90, failed to reach the designed FRR. This is due to compression coming from the continuous bending beam through the beam bottom flange, significantly weakening the column performance. Rib stiffeners between column flanges are proposed to enhance resistance to contact forces from beam flanges during severe fires. However, the simulation found that the steel columns with rib stiffeners might fail immediately after reaching the FRR. Thus, this research introduced the concept of 'reserve fire resistance' (authentic fire resistance to FRR) to evaluate structural steel elements' resilience to fires exceeding the specified FRR, aligning with the concept of reserve capacity of structural resilience to earthquakes. Based on this concept, new limiting temperature design equations were proposed and validated for steel columns derived from their performance, which yielded an average reserve fire resistance of 1.30 herein.

Fire protection is a popular solution to slow down the temperature increase in steel elements subjected to fire, and simple equations, such as the mass lumped formula proposed in EN1993-1-2, may be employed to estimate the steel temperature in the cross-section. The EN1993-1-2 formula assumes that the temperature of the exposed insulation surface and the surrounding gas are equal. This simplification may provide inaccurate results for heavily insulated steel sections. Therefore, a new mass lumped formula was derived, accounting for more accurate boundary conditions considering the heat flux impinging the insulation. On these premises, this work evaluates how the new simple formula fares with respect to the EN1993-1-2 formula. In this respect, a comprehensive comparison with the results of 1-D and 2-D analyses considering several insulation materials and thicknesses of insulation and steel is thoroughly presented. The proposal results in being always safe and better estimates steel temperatures relevant in the structural fire engineering context. Its use is particularly recommended for heavily insulated sections, where the ratio between the insulation and the steel heat capacities is higher than 14, and the EN1993-1-2 formula gives unsafe predictions.

This paper presents two facets of rationalizing natural fires in concrete compartments for structural fire safety . The paper proposes the rate of fire growth corresponding to the maximum possible peak temperature in a compartment, followed by an equation to estimate the equivalent severity between the standard and a natural fire using an energy-based approach. Standard fire curves, applied universally for all design conditions may over- or under-predict real compartment fires. Meanwhile, a full-fledged performance-based design is neither practical nor straightforward to employ in every design situation. The Eurocode parametric temperature–time curves enable engineers to account for specific compartment characteristics, including compartment geometry, building materials, fuel load, and ventilation. Given that different structural fire safety design approaches entail varying levels of complexity, this paper presents simple methods to estimate the worst-scenario compartment fire characteristics . Additionally, fire ratings are established only using standard fire curves, necessitating a scientific means of determining an equivalent severity between natural and standard fires. The energy-equivalence approach used in this paper to establish an equivalent fire severity yields more consistent results than traditional equivalent fire severity methods and empirical formulae for concrete compartments. The proposed equations are developed using simulations of compartment fires and provide insights into the ventilation characteristics that result in the worst-case scenario for both the rate of fire growth and the equivalent time.

Composite steel–concrete beams are employed in buildings and bridges, which may experience elevated temperatures in case of fire. The residual capacity of composite members that survive fire depends on the performance of their shear connectors. This study investigates the capacity of shear studs in composite floors with no metal deck after experiencing elevated temperatures. A 3-D nonlinear finite element model of composite push-out specimens was developed. The model was subjected to the ISO-834 standard fire followed by a cooling-down phase, after which displacement-controlled loading was applied to the model until failure. After validating the model based on experimental data, a parametric study was conducted, in which the load-slip behavior of members employing different concrete compressive strengths, slab thicknesses, shear stud heights, stud diameters, and maximum experienced temperatures was investigated. The thickness of the concrete slab was found to have a noticeable effect on the strength of shear studs before and after heat exposure. The AISC specifications, while overestimating the capacity of unheated shear studs in many cases, were found to underestimate the residual strength of shear studs when used with post-heating mechanical properties. A simplified equation was proposed for quick determination of residual strength of shear studs, which may be used for post-fire structural assessment.