Research On Mechanical Properties Of Steel Structure Reinforced By Fiber Reinforced Polymers

Featured by the light weight,explicit stress path and high tensile strength(2-10 times higher than that of steel),Fiber Reinforced Polymers(FRP)have been extensively applied in steel structure reinforcement technology.As the damaged steel structure cannot be simply replaced by the new ones to realize environmental protection and resource saving,the technology of reusing the damaged steel structure through reinforcement was born and has been developed favorably in China.FRP reinforced steel structure technology enjoys a broad application prospect thanks to its capacity of avoiding secondary stress,superior durability,simple construction,etc.By taking the structural form of the reinforced steel structure with FRP as the research object,this paper studies its mechanical properties by a method that combines experimental study,theoretical analysis and the finite element modeling calculations.The main contents are as below:Static loading tests were carried out against 1 unreinforced testpiece and 7reinforced testpieces with FRP in order to study the mechanical properties of reinforced axial compression steel column with FRP and finally the load-displacement relation curve of the 8 testpieces was obtained.By analyzing the curve it can be seen that the ultimate bearing capacity of the testpiece after reinforcement was improved significantly.This paper also analyzes the influence of parameters such as the number of FRP layers of the reinforced column,the initial load degree and the reinforcement mode on the bearing capacity.This paper derives the bearing capacity formula of FRP reinforced axis compressed steel structures based on the static loading test of the existing reinforced columns,which means deriving its bearing capacity formula using a method combining the equivalent section method with China’s current codes,and simulating the reinforced components with different sections using ABAQUS software to verify the feasibility of its bearing capacity formula.The calculation formula of FRP reinforcement bearing capacity that was finally obtained through correction is found,which therefore brings certain reference value for actual projects.FEM was carried out against the process of destroying the reinforced testpiece by force in the test using the ABAQUS software.By comparing the FEM results with the experimental results,the model was verified basically reliable.After analyzing theparameters that affect the bearing capacity of the FRP reinforced axis compression steel column such as the number of FRP layers and steel pipe width-thickness ratio based on the built FEM,it can be seen that the number of FRP layers shall be determined by considering the impact of economy and cost performance,so as to finally obtain the optimal number of reinforced layers.To study the mechanical properties of steel beams reinforced with FRP,this paper analyzes and studies the FRP stress distribution formula in FRP reinforced steel beams based on the experiments in the references and also establishes a basically accurate FEM for the steel beams reinforced with FRP by referencing the experimental study in references.After analyzing the parameters that affect the bearing capacity of damaged steel beams reinforced with FRP based on the FEM,such as the number of FRP layers and damage length,it can be concluded that a FRP length that could exerts the optimal performance ratio is required instead of a totally paved FRP length to avoid waste;the FRP reinforcement effect is significant,and the bearing capacity even exceeds the bearing capacity of the intact and unreinforced steel beam.The damaged steel beam should be reinforced instead of being replaced directly.