Finite Element Analysis Of Fire Resistance Performance Of Fiber Reinforced Concrete Members With Conventional Rebars

The frequent occurrence of fire accidents has caused domestic and foreign scholars to attach great importance to the research on the fire resistance of concrete components.In addition,high-performance concrete and ultra-high-performance concrete,which are widely used at present,are prone to spalling or even burst under fire.As a result,the fire resistance of concrete components is reduced.The incorporation of fibers not only inhibits the occurrence of concrete bursting,but also significantly improves the residual tensile performance of concrete,which in turn affects the fire resistance of concrete components.Scholars at home and abroad have relatively little research on the fire resistance of reinforced fiber reinforced concrete components under fire,and the cost of fire resistance test of the components is high and the operation is difficult.Therefore,based on the experiments reported in the literature,the finite element analysis of the temperature field and deformation properties of fire-exposed reinforced fiber reinforced concrete members is carried out and the influence of different parameters on them is studied,which provides a theory for the fire resistance analysis and design of reinforced fiber reinforced concrete members.The main research contents and conclusions are as follows:(1)Sort out and summarize the domestic and foreign literature on the thermal parameters and mechanical parameters of steel bars and fiber concrete at high temperatures.The most important thing is that the incorporation of fibers will improve the tensile properties of concrete to a certain extent,and the tensile stress-strain relationship of fiber concrete must consider the influence of fibers.Therefore,when considering the tensile stress-strain relationship of fiber reinforced concrete at high temperature,the tensile stress-strain relationship model recommended by the European Model Code is improved.Select reasonable parameters to establish a two-dimensional(2D)finite element model of reinforced fiber reinforced concrete beams,and use Python to carry out computer programming to perform finite element analysis on the fire resistance of the beam,and obtain the bending moment-curvature relationship curve of the beam mid-span and calculate it based on the principle of virtual work.The deflection of the beam in the middle of the span is compared with the existing literature test data to verify its rationality.The steel bar temperature and component deformation limits are used as evaluation indicators to analyze the fire resistance performance of reinforced fiber reinforced concrete components.The study found that the fire resistance of reinforced fiber reinforced concrete beams should adopt the deflection limit of the beam in the middle of the span as the failure criterion.(2)With the aid of ABAQUS finite element software,a three-dimensional(3D)finite element analysis was carried out on the fire resistance performance of fired reinforced fiber reinforced concrete beams using the method of thermal and mechanical sequential coupling.The analysis results of the 2D finite element model and the 3D finite element model are compared,and the results show that the analysis results of the 3D finite element model are closer to the experimental results.Based on the applicability and accuracy of the 3D finite element model,a parameter analysis of the temperature field and mid-span deflection of the beam section is carried out.The main influencing factors of the temperature field of the beam section are different heating curves and the thickness of the protective layer,and the main influencing factors of the deflection of the beam in the middle of the span are the load level and the fiber content.Compare the deformation curves of concrete beams without fiber and concrete beams with fiber.The results show that adding fibers to concrete can effectively reduce the mid-span deflection of the beam,increase ductility,and improve the fire resistance of reinforced concrete beams.The verification of the 3D finite element model of the reinforced fiber concrete slab shows that the established finite element model is also applicable to the reinforced fiber concrete slab.(3)With the aid of ABAQUS,a finite element model of reinforced fiber reinforced concrete column is established,and the temperature field and axial deformation of the column section are analyzed.The main influencing factor of the temperature field of the column section is the fire surface,and the main influencing factor of the axial deformation of the column is the reinforcement ratio and the axial compression ratio.