ANALYSIS OF CARBONIZED SPEED AND RESIDUAL SECTION OF STEEL-TIMBER CONNECTION

The demand for steel-timber hybrid structures is increasing, particularly in mid-rise and high-rise buildings. In these hybrid systems, connection hardware playsacrucial role; however, its high thermal conductivity can create vulnerabilities at the joints under fire conditions. To address this issue, this study evaluates the thermal distribution of connection hardware with fire-resistant coatings using finite element analysis (FEA). Based on previous studies, five analytical models were developed, incorporating key variables such as the presence of connection hardware, the application of fire-resistant coating, and coating thickness, all subjected to a 3-hour fire exposure scenario. The analysis results indicate that connection hardware accelerates the formation ofachar layer at steel-timber joints. However, fire-resistant coatings were found to significantly reduce the char rate and thickness of timber, thereby enhancing fire resistance performance. Notably, as coating thickness increased, the char layer formation within the timber was delayed, leading toagreater residual cross-sectional area. In specimens with a 15 mm fire-resistant coating, the steel temperature remained below its critical threshold throughout the 3-hour fire exposure, demonstrating the feasibility of achieving 3-hour fire resistance performance. Furthermore, by analyzing the char thickness per unit time through differential charring rates, this study suggests thatamore accurate fire resistance design can be achieved compared to traditional methods.