Reliability Analysis Of Reinforced Concrete Beams Strengthened With Bonded Steel Plates After Fire

As a traditional reinforcement method,steel-bonded reinforcement method has been widely used in reinforcement engineering.At present,steel-bonded reinforcement method has a very mature understanding.However,due to the complexity of mechanical properties of reinforced concrete members after fire,there is little research on the reliability of steel-bonded reinforcement of reinforced concrete beams after fire.It is very important to study the reliability of reinforced concrete beams strengthened by bonded steel plates after fire for guiding the reinforcement and repair of reinforced concrete structures after fire.In order to calculate the bearing capacity reliability of reinforced concrete beams strengthened with bonded steel plates more accurately,this paper considers the influence of different strengthening schemes,thickness of concrete protective layer,load-effect ratio and fire time on the reliability of reinforced concrete beams strengthened with bonded steel plates after fire,and conducts in-depth research and analysis.The specific research contents and results of this paper are as follows:(1)The thermal performance formula of reinforced concrete members after fire is introduced,and ABAQUS is redeveloped by programming in Python language.The calculation method of the maximum temperature field of reinforced concrete members after fire is proposed,and the method is verified in detail in the actual fire situation of reinforced concrete members.The results show that the method of calculating the maximum temperature field of reinforced concrete members after overfire can accurately calculate the maximum temperature of reinforced concrete members after overfire,which is the basis of subsequent reliability calculation.(2)The formulas of material properties and flexural capacity of reinforcedconcrete members after fire are introduced.The formulas for calculating flexural capacity of reinforced concrete beams strengthened by bonded steel after fire are derived.Based on the calculation method of the maximum temperature field of overfire proposed in this paper,different load-effect ratios,fire time,thickness of concrete protective layer and thickness of reinforcing steel plate are considered.The influence of steel plate thickness and other factors on the reliability index of flexural bearing capacity of reinforced concrete beams is analyzed by using MATLAB software.The reliability of the flexural capacity of reinforced concrete beams was calculated and analyzed.The results show that the reliability index of the flexural capacity of reinforced concrete beams decreases with the increase of the load effect ratio,increases with the thickness of the strengthened steel plate,and decreases with the increase of the fire time.Moreover,the thickness of concrete protective layer can delay the decline of flexural capacity of reinforced concrete beams in fire to a certain extent.(3)Considering the influence of hoop plate specification,fire time,load effect ratio and concrete protective layer thickness on the reliability of reinforced concrete beam shear capacity,and analyzing and calculating,the results show that the shear capacity reliability index of reinforced concrete beams as the load effect ratio increases,it decreases as the pitch of the reinforced ferrule increases,and decreases as the fire time increases.The thickness of the concrete protective layer can alleviate the mechanical properties of the stirrup to a certain extent in the fire,but the impact on the shear reliability index is not great.