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Featured Application: Numerical results to determine the fire resistance of ultra-high-strength steel using different heating rates. Ultra-High-Strength Steel (UHSS) offers several advantages over normal carbon steel, promoting exceptional strength, reducing self-weight, improving fire resistance, enhancing durability, and reducing material consumption. These advantages result in cost savings and sustainable engineering construction. The 3D numerical model is based on Geometrical and Materially Nonlinear Imperfection Analysis (GMNIA) and determines the fire resistance of different cross-section columns. The model is validated with experimental tests, with a maximum relative error of 11%. A parametric analysis is presented, based on 252 simulations, assuming three heating rates, two different cross-sections, two different thicknesses, three lengths, and seven load levels. The fire resistance depends on the heating rate, but the critical temperature is almost equal and independent of the heating rate, if one assumes implicit creep in the constitutive material model. The fire resistance decreases with the load level, as expected. The thickness effect of the hollow section is almost negligible in the fire resistance of UHSS columns. The fire resistance decreases more in higher load levels for slender columns. Columns with Circular Hollow Sections (CHSs) generally show higher fire resistance than hybrid columns in longer columns, but the hybrid columns are subject to much higher loads. New design formulas are presented for the critical temperature of UHSS columns, depending on the load level and slenderness of two different cross-sections. [ABSTRACT FROM AUTHOR] more...

This study investigates the thermal buckling in railway infrastructures, which can cause derailments and safety risks. The research analyses the influence of various parameters on thermal buckling, focusing on misalignment and ballast resistance. Using a finite element model, curved and tangent tracks are simulated, considering rail sections, sleeper materials, fastener stiffness and initial imperfections. Results demonstrate that ballast resistance is the most critical factor, with compacted ballast increasing buckling temperatures by up to 127%. Additionally, rail imperfections significantly impact temperature increases. A new design guide is proposed for operating conditions under different conditions. [ABSTRACT FROM AUTHOR] more...

The Light Steel Frame (LSF) construction system is a method that utilizes light and galvanized steel structures composed of cold‐formed profiles. These profiles come together to create both structural and non‐structural frames, with various coatings. However, in fire situations, the metal structure can be affected, altering its mechanical properties and potentially leading to collapse. This study examined the behavior of a Steel Frame structural panel coated with gypsum boards during a fire, using numerical analyses with the ANSYS software. The results provided insights into the fire resistance of the structure. [ABSTRACT FROM AUTHOR] more...

Light Steel Frame (LSF) walls are widely used in building structures, used as partition walls and load bearing walls. The LSF is usually protected by layers of homogeneous plates or composite plates, with or without insulation materials in the cavity. This investigation presents the experimental and the simulation results of composite LSF walls in reduced scale and full scale, based on variable load levels (20 to 80%). The numerical model is validated with experimental results, at reduced and full scale, both at room temperature and under fire conditions. This modelling technique can follow the thermal and mechanical degradation of the protection layers of the LSF wall and determine the fire rating for load (R) and insulation (I). The fire resistance (R) decreases with the increase of the load level, being the critical temperature of the steel structure presented by the maximum temperature of the Hot Flange (HF). A new proposal is presented for the critical temperature of the LSF, based on the maximum temperature of the LSF during the fire. The insulation ability is also predicted for different protection materials. Relevant conclusions are presented to increase the insulation ability of LSF walls. [ABSTRACT FROM AUTHOR] more...

Most of the studies involving composite slabs under fire follow the standard fire scenario described by the ISO 834 curve, disregarding the cooling-phase. However, recent studies show that this phase is equally important, as it can lead to the collapse of the structure. Therefore, the present research carried out a parametric study, using numerical models, validated through experimental tests, to evaluate the thermal behaviour of the composite slabs components under natural fire. The results showed that the maximum temperatures in the reinforcement bars occur during the cooling-phase, reaching temperatures up to 300% higher than at the heating-phase, on the steel deck occur at the end of heating, and that the concrete thickness above the steel deck influences the temperature of these components. Also, during the cooling-phase, a "heat bubble" effect is observed on the ribs of the composite slabs, where the reinforcement bars are normally placed. These results highlight the importance of considering different natural fire scenarios, in the structural performance and safety of composite slabs, since during the cooling-phase there is still heat transfer between the elements, which can lead to slab failure. New parameters are proposed to find the temperature of each component for different fire ratings. [ABSTRACT FROM AUTHOR] more...

Metal machining is one of the most important manufacturing processes in today's production sector. The tools used in machining have been developed over the years to improve their performance, by reducing the cutting forces, the friction coefficient, and the heat generated during the cutting process. Several cooling systems have emerged as an effective way to remove the excessive heat generated from the chip-tool contact region. In recent years, the introduction of nano and micro-textures on the surface of tools has allowed to further improve their overall performance. However, there is not sufficient scientific data to clearly show how surface texturing can contribute to the reduction of tool temperature and identify its mechanisms. Therefore, this work proposes an experimental setup to study the tool surface characteristics' impact on the heat transfer rate from the tools' surface to the cooling fluid. Firstly, a numerical model is developed to mimic the heat energy flow from the tool. Next, the design variables were adjusted to get a linear system response and to achieve a fast steady-state thermal condition. Finally, the experimental device was implemented based on the optimized numerical model. A good agreement was obtained between the experimental tests and numerical simulations, validating the concept and the implementation of the experimental setup. A square grid pattern of 100 μm × 100 μm with grooves depths of 50, 100, and 150 μm was introduced on cutting insert surfaces by laser ablation. The experimental results show that there is a linear increase in heat transfer rate with the depth of the grooves relatively to a standard surface, with an increase of 3.77% for the depth of 150 μm. This is associated with the increase of the contact area with the coolant, the generation of greater fluid turbulence near the surface, and the enhancement of the surface wettability. [ABSTRACT FROM AUTHOR] more...

This paper presents a finite-element-based computational model to evaluate the thermal behaviour of composite slabs with a steel deck submitted to standard fire exposure. This computational model is used to estimate the temperatures in the slab components that contribute to the fire resistance according to the load-bearing criterion defined in the standards. The numerical results are validated with experimental results, and a parametric study of the effect of the thickness of the concrete on the temperatures of the slab components is presented. Composite slabs with normal or lightweight concrete and different steel deck geometries (trapezoidal and re-entrant) were considered in the simulations. In addition, the numerical temperatures are compared with those obtained using the simplified method provided by the standards. The results of the simulations show that the temperatures predicted by the simplified method led, in most cases, to an unsafe design of the composite slab. Based on the numerical results, a new analytical method, alternative to the simplified method, is defined in order to accurately determine the temperatures at the slab components and, thus, the bending resistance of the composite slabs under fire conditions. [ABSTRACT FROM AUTHOR] more...

This manuscript presents the results of numerical research regarding the thermal buckling on railway tracks. High temperatures may cause thermal buckling on the railways and due to this fact speed restrictions are often issued to reduce the probability of derailments. Railways are subject to thermal and mechanical loads in which, given some circumstances, buckling may take place. Continuous welded rail (CWR) is more prone to this effect than jointed rails since the longitudinal displacement is restrained. This research is focused on the effect of the track gauge, rail profile, initial imperfection amplitude, sleeper's elasticity modulus, torsional resistance of fastenings, and ballast resistance on the thermal buckling of railways. A total of 144 simulations were developed, concluding that the imperfection level and ballast resistance are the most affecting parameters on the buckling temperature. [ABSTRACT FROM AUTHOR] more...

Composite slabs with steel deck combine the load-bearing resistance of the steel deck and rebar with the compressive resistance of the concrete (components). Unprotected composite slabs may be exposed to natural fire conditions from below, and steel reduces its load-bearing capacity during the heating stage. In short fire events, with limited deformations, the composite slabs can recover the load-bearing capacity during the cooling stage. This research presents the validation of the numerical model and the development of a parametric study, to evaluate the load-bearing capacity during the fire event. This method includes a time step procedure, based on the average temperature calculation for each component, including the reduction coefficients applied to the design strength of each material. A new proposal is also presented to evaluate the residual loadbearing capacity. In some circumstances, the residual load-bearing can be reduced by more than 20%. The results showed that the highest variation in the load-bearing resistance of composite slabs occurs when the steel temperatures are between 20 and 600°C, after this temperature, the steel has already lost most of its mechanical strength. Moreover, it was observed that different heating rates and different cooling rates influence the rate of the reduction and recovery of the load-bearing capacity. It was also noticed that the lowest load-bearing capacity of the composite slabs was reached after the end of the heating phase, showing that the stability of the element during the heating phase does not guarantee fire safety during the cooling phase. [ABSTRACT FROM AUTHOR] more...

This investigation analyses the influence of the depth and the distance between studs on the fire resistance of lightweight timber-framed (LTF) walls lined with gypsum plasterboards. The simplified model used to determine the fire resistance in Eurocode EN 1995-1-2 provides very conservative values, as few parameters are considered. The new generation of Eurocode EN 1995-1-2 includes an upgrade of the simplified model, allowing us to predict the fire resistance of LTF wall assemblies more accurately. This separating function method considers the number, the thickness and the material of the protection layers, but does not explicitly consider the variation of the depth and the distance between the studs for the calculation of the insulation time of the assembly, besides including some limitations for both parameters. To demonstrate the influence of these parameters, 36 numerical simulations were carried out using the finite element method previously validated with experimental tests. The results obtained from the parametric analyses confirmed that such parameters affect the fire resistance of the LTF wall assemblies in a significant way. In addition, the results revealed an important contribution in the study of LTF wall assemblies against fire resistance, demonstrating the need for including extra geometric parameters in the simplified model in order to increase the accuracy of current models. [ABSTRACT FROM AUTHOR] more...

Valorization of industrial low-value side-streams are of great interest, contributing to boosts in the circular economy. In this context, lignin side-streams of the pulp and paper industry were oxypropylated to produce biobased polyols and tested in the synthesis of rigid polyurethane (RPU) foams. E. globulus lignins, namely a lignin isolated from an industrial Kraft black liquor and depolymerized lignins obtained as by-products of an oxidation process, were used. RPU foams, synthesized with 100% lignin-based polyols and using a 1.1 NCO/OH ratio, were characterized concerning apparent density, morphology, thermal conductivity, thermal stability, and heat release rate (HRR). Foams containing the lignin-based polyols presented densities varying from 44.7 to 112.2 kg/m3 and thermal conductivity in the range of 37.2–49.0 mW/mK. For the reference foam (sample produced with 100% wt. Daltofoam TP 32015 polyol), values of 70.9 kg/m3 and 41.1 mW/mK were obtained, respectively. The achieved results point out the viability of using the generated lignin-based polyols at 100% content in RPU foams, mainly when depolymerized lignins are used. Moreover, fire retardancy was favored when the lignin-based polyols were introduced. The proposed strategies can contribute to establishing the integrated pulp and paper biorefinery concept where material synthesis (polyols and RPU foams) can be combined with chemical production (vanillin and syringaldehyde). [ABSTRACT FROM AUTHOR] more...