Research And Analysis On The Flexural Performance Of H-shaped Steel Beams Strengthened By Prestressed Carbon Fiber Reinforced Plastic (CFRP) Plates

Steel structure has many advantages,such as light weight,high strength,good plasticity and toughness,superior seismic performance,short construction period and easy indust-rialization of construction industry.It is widely used in civil buildings,bridges,pipelines and masts.Recently,with the increase of service time,the accumulation of damage,the im-provement of load grade and the change of service function,etc.Components do not meet the requirements of normal use and have potential safety hazards.It is necessary to reinforce the original components.Prestressed CFRP plate has many advantages over traditional rein-forcement measures in strengthening steel structures.At present,the research and application of CFRP plate in strengthening and repairing concrete structures are mature,but there are still many problems to be explored in strengthening and repairing steel structures.Therefore,this paper studies the strengthening of four-point bending steel beams with pre-stressed CFRP plates In this paper,the effects of various parameters on the interface stress,bearing capacity and stiffness of CFRP plate after reinforcement are analyzed.The main contents are as follows:(1)The research background of H-section steel beam strengthened by prestressing CFRP plate is briefly described.Summarize the existing research results at home and abroad from three perspectives of theoretical analysis,experimental research and finite element simulation.It is found that few studies have been carried out on H-shaped steel beams strengthened by prestressing CFRP slabs.Therefore,the content of this paper is determined by summarizing.(2)The calculation formula of interfacial stress is deduced by using elastic theory.The effects of thickness,width,length,prestress,modulus of elasticity and thickness of adhesive layer on interfacial shear stress of CFRP plate are analyzed.The results show that the interfacial shear stress in the midspan is very small,approximate to zero,and can be neglected.However,there is a serious stress concentration in the range of 100 mm at the end of CFRP plate.The maximum shear stress at the end of CFRP plate increases with the increase of the thickness,length and prestress of CFRP plate,and decreases with the increase of the thickness of adhesive layer.Therefore,attention should be paid to adjusting these values in design to avoid excessive interfacial shear stress and to influence reinforcement performance.In addition,the effect of stress concentration can also be reduced by installing anchorage at the end of the interface to avoid cracking.(3)The modeling steps of finite element software ABAQUS are described.By carefully reading the relevant literature,the modeling method and the simulation method of prestressing force of H-section steel interface strengthened by prestressing CFRP plate are determined.Finally,the validity of the model is verified by comparing the experimental values in the existing literature with the results of the finite element model,which shows that the model can be used in this study.(4)Using the finite element modeling method determined in this paper.ABAQUS software is used to analyze the effects of length ratio,width ratio,thickness ratio,clastic modulus ratio and prestress level on ultimate bearing capacity and stiffness after reinforcement.The optimum range of some parameters is given for engineers.(5)Based on the formulas for calculating the bearing capacity and deflection of ordinary steel beams,the strengthening coefficient of bearing capacity and stiffness are introduced.The ultimate bearing capacity and stiffness of H-section steel beams strengthened with pre-stressed CFRP slabs are calculated by ABAQUS software.Simplified formulas for calculating the reinforcement coefficient of bearing capacity and stiffness are obtained by nesting method,and the correctness of the approximate formulas is verified.