火灾后部分预制蜂窝型钢超高性能混凝土开孔梁受弯性能试验研究OA

To optimize the pipeline layout and enhance the mechanical behavior,constructability,durability,and fire resistance of steel reinforced concrete beams,this study proposed a novel partially precast castellated steel reinforced ultra-high performance concrete(UHPC)beam with web openings(OPPCSRC beam),which integrated castellated steel,hybrid-fiber reinforced ultra-high performance concrete(H-UHPC),and prefabricated composite construction techniques.Flexural behavior tests were conducted on two partially precast castellated steel reinforced UHPC beams(PPCSRC beam)and four OPPCSRC beams under room-temperature and post-fire conditions.The effects of fire exposure,web openings,and opening-reinforcement configuration on fire-induced damage characteristics,temperature field,and mechanical behavior of the beams were investigated.The results indicate that the post-fire and room-temperature specimens exhibit identical failure modes.Fire exposure causes significant reductions in flexural capacity,stiffness,and ductility by 9.7%-18.6%,27.2%-35.3%,and 5.4%-41.4%,respectively.The reductions in flexural capacity and stiffness are similar for OPPCSRC and PPCSRC beams,whereas the ductility deterioration is markedly more severe for OPPCSRC beams.Although the opening-reinforcement configuration effectively improves the room-temperature flexural behavior of OPPCSRC beams and significantly mitigates the post-fire reduction in flexural capacity,its ability to restrain stiffness and ductility degradation remains limited.Based on temperature-field finite element analysis,the beam cross-section was divided into several temperature zones.Using an area-weighted average method,a comprehensive reduction coefficient for concrete strength was determined.Finally,a flexural capacity calculation method for PPCSRC and OPPCSRC beams at room temperature and after fire exposure was proposed.The calculated results exhibit good agreement with the experimental data.