| The development of large-span space structure to Super-large-span space structure is faced with such problems as large proportion of structure self-weight,limited service life,easy corrosion and high maintenance cost of traditional materials.Using the characteristics of CFRP,such as light weight,high strength and good durability,CFRP-steel tube composite specimens are formed,which can effectively improve the structural properties of steel tubes.There are many studies on CFRP-steel tube composite specimens by scholars at home and abroad,but most of them are short columns or long columns.There are few studies on full-scale specimens,and a complete set of systematic results has not yet been formed.In this paper,through experimental research and finite element analysis of full-scale specimens,the mechanical characteristics of this new type of components are obtained.Firstly,the mechanical properties of CFRP-steel tube composite specimens under axial load were studied.Eight specimens were tested under axial tension and 15 specimens were tested under axial compression.The effects of the number of fiber layers,the length of end thickening section and the direction of fiber on the bearing capacity and failure modes of axially tensioned and compressed composite specimens are studied.The experimental results of axial tension show that the number of CFRP layers has a great influence on the strength and ductility(secondary stiffness)of the specimens when the length of the endthickening section reaches a certain limit,and the failure of the composite specimens eventually shows that CFRP breaks,and then only the steel tube is subjected to force,and the overall ductility performance is better.The results of axial compression test show that CFRP can improve the strength and stiffness of composite specimens to a certain extent,while the direction and layers of CFRP have a greater impact on the bearing capacity and failure mode of components.Secondly,based on the finite element analysis software ABAQUS,a refined finite element model of CFRP-steel tube composite specimens is established.The results of finite element simulation are compared with the experimental results,and they are in good agreement.The finite element model can accurately predict the mechanical properties of CFRP-steel tube composite specimens.Based on the above finite element model,the deficiencies of the experimental research are supplemented,and the stress and strain distributions of CFRP and steel tube in full length,as well as the law of stress development and variation with load are studied.The results of finite element analysis under axial tension show that when the number of CFRP layers is within a certain range,the increase of CFRP layers can significantly improve the bearing capacity of specimens,and the existence of end-thickening section changes the stress distribution of steel tube and CFRP in composite specimens.The results of finite element analysis under axial compression show that increasing the number of CFRP layers in a certain range does not significantly improve the stability bearing capacity,but the order of CFRP bonding has a great influence on the stability bearing capacity;for the same CFRP bonding mode,the larger the slenderness ratio,the greater the improvement of the stability bearing capacity.Finally,based on the experimental research and numerical simulation results,the stress mechanism of composite specimens is analyzed in detail.Based on the CFRP-steel tube composite specimens stress model,the converted section method,Perry formula and China's "Steel Structure Design" of CFRP reinforced steel structure design guidebook "Code for Metal Structures Reinforced by External Fiber Reinforced Materials" compiled by CIRIA,UK are used.According to the calculation method of the bearing capacity of pure steel tube in the Standard,the correction coefficient of bearing capacity is put forward,and the calculation formula of the bearing capacity of CFRP-steel tube composite specimens is deduced.The results show that the theoretical formula can well predict the bearing capacity of this kind of composite specimens,and can provide useful reference for engineering application. |
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