Flexural Performance Of Hybrid Fiber-reinforced Self-consolidating Concrete Beams Before And After High Temperature

Fire is one of the most serious disasters for tunnels. Serious casualties, great social influence and economic losses will be suffered during and after fire exposure in tunnels. Lots of tunnel fire cases show that fire often leads to spalling and degradation of mechanics performance of the tunnel lining structure, thus causes serious damage on tunnel lining structure, reduces the bearing capacity of structure, safety and durability. However, tunnel lining structure is difficult to dismantle, along with the more and more use of fiber reinforced self-consolidating concrete (FRSCC) and hybrid fiber reinforced self-consolidating concrete (HyFRSCC) in the tunnel lining segment, to quantify the degree of high temperature degradation of tunnel segment after fire is of great significance. Based on the National Natural Science Fund Project (51078058):Influence of hybrid fibers on crack and mechanical properties of tunnel segment and the National Natural Science Fund Project (51478082): Performance and mechanism of a new type hybrid fiber reinforced cementitious composite based on multi-level structure, spalling behavior and flexural performance of FRSCC and HyFRSCC beams during and after fire exposure were investigated in this dissertation.The main contents are as follow:(1) Flexural performance and fiber effect of simply supported HyFRSCC beams before fire exposure was investigated. The main innovative work is to propose a new calculation model by taking the effects of hybrid fibers into consideration for ultimate bearing capacity of simply supported HyFRSCC beams, for crack width and deflection of simply supported HyFRSCC beams at room temperature.(2) Symmetric inclination beam was employed to simulate the mechanical characteristics of tunnel segment. Flexural performance and fiber effect of symmetric inclination HyFRSCC beams before fire exposure was investigated. The main innovative work is to propose a new calculation model by taking the effects of hybrid fibers into consideration for ultimate bearing capacity of symmetric inclination HyFRSCC beams before fire exposure.(3) Spalling of HyFRSCC during fire exposure was investigated based on the vapor pore pressure theory. The main innovative work is to take the lead in carrying out the experimental test of HyFRSCC exposed to fire. Meanwhile, a vapor pressure prediction formula which takes the effect of hybrid fibers into consideration was proposed.(4) Temperature field and isotherm of HyFRSCC during fire exposure were investigated by experimental test and numerical modeling method.(5) Spalling of HyFRSCC during fire exposure was investigated based on the vapor pore pressure theory. The main innovative work is to take the lead in carrying out the experimental test of HyFRSCC exposed to fire. Meanwhile, a vapor pressure prediction formula which takes the effect of hybrid fibers into consideration was proposed.(6) Flexural performance and fiber effect of simply supported HyFRSCC beams after fire exposure was investigated. The main innovative work is to propose a new calculation model by taking the effects of hybrid fibers into consideration for ultimate bearing capacity of simply supported HyFRSCC beams after fire exposure.(7) Flexural performance and fiber effect of symmetric inclination HyFRSCC beams after fire exposure was investigated. The main innovative work is to propose a new calculation model by taking the effects of hybrid fibers into consideration for ultimate bearing capacity of symmetric inclination HyFRSCC beams after fire exposure.