Experimental and numerical investigation on fire resistance of PEC members with fire protection

This study investigates the fire resistance of partially encased composite (PEC) members through experiments and finite element (FE) analysis. Fire tests were conducted on three T-shaped PEC beams and six rectangular PEC columns, each with fire-proof coating, exposed to the ISO 834 standard fire curve. Results showed that all beams experienced flexural deformation and concrete cracking, and satisfied the two-hour fire resistance requirement. FE models were developed to simulate temperature development, distribution, and thermo-mechanical behavior, with numerical results matching experimental outcomes. A parametric study was conducted to investigate the effects of coating thickness, section dimensions, and load ratio on temperature development and fire resistance. It was found that increasing the coating thickness from 7.0 mm to 11.0 mm reduced the peak temperature by approximately 150°C after 3 hours of fire exposure. Additionally, the load ratio significantly impacted the fire resistance of PEC beams, while section dimensions had minimal influence. Based on these findings, a practical design method for predicting the load capacity of PEC beams under elevated temperatures was proposed, showing good agreement with experimental and FE results.