The fire resistance performance of steel beams is of utmost importance to the fire safety of building structures and personnel evacuation. To address the deviation in the assumption of uniform temperature distribution in traditional studies, this study conducted multiple simulation tests. It was found that when the size of the vent was reduced by 50%, the difference in the heating rate in the early stage of the fire was 30% to 50%. Increasing the load ratio from 0.2 to 0.8 can significantly reduce the critical temperature of the steel beam by 15% to 20%, and the corresponding critical temperature is reduced from 670 °C to 565 °C. Based on parametric analysis, a simplified evaluation model of critical temperature for Q460 high-strength steel beams is proposed. The calculation error of the model is less than 5%, which provides a theoretical basis for the whole process of fire protection design. The research achievements break through the limitations of traditional methods and offer innovative approaches to predicting the fire resistance performance of steel beams and their optimized design.

The time–temperature curve serves as a fundamental input for calculating structural fire resistance. Accurate acquisition of this curve is essential for designing structures to withstand fire incidents effectively. In this study, fire test temperature variation data were analyzed to develop a comprehensive understanding of the temperature-rise curve, categorized into three primary phases: Confined Fire Phase, Reignition Phase, and Flashover to Fully Developed Fire. To address non-uniform temperature distribution, a temperature reduction coefficient was introduced into the temperature-rise curve formula. This coefficient was derived by fitting experimental temperature data from multiple fire tests, enhancing the formula’s applicability to compartment fires. Furthermore, accounting for non-uniform temperature distribution along compartment height is critical for accurate thermo-mechanical simulations of structural components. To simplify calculations, layer-specific reduction coefficients were proposed: top area (x ≥ 0.7H): 1.0; middle area (x < 0.7H): 0.73; bottom area (x ≤ 0.4H): 0.34. These coefficients, determined through numerical simulations, exhibit broad applicability. In conclusion, precise characterization of temperature-rise curves is vital for structural fire resistance assessment. The proposed methodology and reduction coefficients improve the robustness and generalizability of thermo-mechanical simulations in evaluating structural fire performance.

To establish the restoring force model of the cross-slanted self-buckling-restrained corrugated steel plate shear wall (hereafter abbreviated as CCSPW), finite element parametric analysis was conducted on the hysteretic behavior of the CCSPW by considering four key influencing factors: the axial compression ratio, aspect ratio, inclination angle, and end plate thickness. Based on the obtained hysteresis curves and skeleton curves, the skeleton curves were dimensionlessly normalized and regression-fitted to establish a trilinear skeleton curve model together with the functional expressions for each loading stage. Furthermore, the stiffness-degradation laws of different loading and unloading paths were analyzed, and the corresponding stiffness-degradation functions were proposed to construct the restoring force model of CCSPW. The restoring force model was verified by comparing the calculated results with the finite element analysis results. The results indicate that CCSPW exhibits favorable energy-dissipation capacity and high bearing capacity; in particular, the energy-dissipation capacity weakens for the specimens with small aspect ratios, for which noticeable pinching of the hysteresis curves is observed. The proposed restoring force model is in good agreement with the finite element results, providing a theoretical reference for the seismic analysis of this shear wall.

A novel thermal conductivity prediction model was developed to address the complex influence of pore structure in porous materials. This model incorporates pore size (d) and a pore distribution parameter (t) to calculate the material’s thermal conductivity. To validate the model’s accuracy, geopolymer foamed concrete (GFC) samples with varying pore structures were fabricated. These utilized ground granulated blast furnace slag (GGBS) as the precursor, a mixed solution of sodium hydroxide (NaOH) and sodium silicate as the alkaline activator, and sodium stearate (NaSt), hydroxypropyl methylcellulose (HPMC), and sodium carboxymethyl cellulose (CMC-Na) as foam stabilizers. Conventional pore size characterization techniques exhibit limitations; consequently, this research implements a high-fidelity machine vision-driven image analysis methodology. Pore size measurement is achieved through a combined technical approach involving equivalent diameter modeling and morphological optimization. The feasibility of the proposed theory is validated by our experimental data and data from previous literature, with the error between experimental and theoretical values maintained within 5%. The value of t increases with increasing porosity and increasing disorder in pore distribution. Based on the experimental data obtained in this study and the research data from previous scholars’ studies, the t value for porous materials can be categorized according to porosity: when porosity is approximately 30%, t ≈ 0.9; when porosity is 55~65%, t ranges from 1.2 to 1.3; and when porosity is approximately 80%, t ranges from 1.9 to 2.2.

During fires, the temperature difference between indoor and outdoor environments induces out-of-plane deformation in steel studs. Due to the differential coefficients of thermal expansion between panels and steel, the panels exert a restraining effect on the studs. However, there remains a lack of systematic experimental and theoretical models addressing the failure modes, restraining mechanisms, and synergistic effects of various panels on steel studs. This study conducted high-temperature bending tests to compare the failure modes, load–displacement curves, and key mechanical parameters (peak load, elastic stiffness) of connections combining steel studs with three types of panels: autoclaved lightweight concrete (ALC) panels, fire-resistant gypsum boards, and medium-density calcium silicate board. The research clarifies the constraining effect and temperature sensitivity of different panels. Based on experimental data, a bending constitutive model was developed to quantify the attenuation of the out-of-plane constraining effect at elevated temperatures. The results indicate that the load–displacement curves exhibit three distinct stages: Elastic Ascending Stage, Elastoplastic Ascending Stage, and Post-Peak Stage. A two-stage bending constitutive model was proposed and formulated. Comparison between numerical simulations and experimental specimens in terms of failure modes and characteristic parameters demonstrated that simplifying the panels as spring elements, with stiffness defined by the proposed bending constitutive model, yields errors within 15%, confirming the accuracy of the model. This study systematically investigates the influence of sheathing panels on the high-temperature out-of-plane mechanical behavior of cold-formed steel studs, innovatively proposes a two-stage bending constitutive model, provides theoretical and data support for cold-formed steel structural fire-resistant design, and offers new perspectives and methodologies for future research.