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.

Ultra-High-Ductility Engineered cementitious composite (ECC), derived from systematic micromechanical design, is a fiber-reinforced cementitious material exhibiting high ductility under tensile and flexural loading. As a critical mechanical index for civil engineering materials, flexural strength is irreplaceable in the design of flexural members and the assessment of structural safety. This paper reviews the influence of water-to-cement ratio, fiber volume fraction, and cement-to-fly-ash ratio on the mechanical performance of ECC, with particular emphasis on the governing law of flexural strength.

An investigation into the influence of different fiber types on the flexural performance of cementitious matrices should not only focus on the effects of individual fibers but also consider the hybridization effects between different fibers. To evaluate the flexural behavior of fiber-reinforced cementitious composites, referred to as Engineered Cementitious Composites (ECC), this study selected two types of synthetic fibers-polyethylene fiber (PE) and polypropylene fiber (PP)-as the experimental variables. The equivalent flexural toughness and equivalent flexural strength were analyzed through standardized flexural testing. The results indicate that specimens incorporating solely PE fibers exhibited superior performance, achieving Class I ratings for both equivalent flexural toughness and strength. In contrast, specimens containing a hybrid blend of PP and PE fibers demonstrated relatively lower performance, failing to meet Class I criteria for either parameter.

Ultra-high Ductility Engineered Cementitious Composites (ECC), a class of ultra-high ductility cement-based concrete materials, are fiber-reinforced composites systematically engineered through micro-mechanical principles to achieve exceptional strain capacity under both tensile and shear loading conditions. ECC materials have been extensively implemented in civil engineering applications due to the ultra-high ductility and crack resistance. In order to meet the needs of actual engineering appliances, it is necessary and crucial to develop and apply macroscopic constitutive models with high efficiency to predict the mechanical behavior of ECC. Consequently, this paper selects several existing compressive constitutive models of ECC and evaluates the performance of these models. All the selected models are empirical and phenomenological models which are established to describe the macro-mechanical properties of ECC for the convenience of practical engineering. It can be concluded that Model I in this study produces more accurate predictions compared to other existing models based on the collected experimental results.

Up to now, many models of fiber reinforced polymer (FRP)-confined concrete cylinder (or concrete circular column) have been established to predict the constitutive relationship with strain-hardening behavior. This investigation concentrates on the performance of the selected conventional type of FRP confined concrete cylinders, especially for the prediction of the second stiffness, E ₂ , of stress-strain curve. In order to efficiently evaluate prediction level, test data including unconfined concrete strength ranging from 22.7 to 169.7 MPa, circular column diameters covering 100∼610 mm, and FRP layer up to 15 plies, is gathered. The comparison between test data and collected models demonstrates that some models can effectively predict axial properties of E ₂ for concrete circular columns strengthened by conventional type FRP jackets.