| The biggest problem faced by buildings is the natural disasters,such as the impact of fire,earthquake,acid rain and other corrosive effects,which will lead to damage the building.Researchers put forward the composite structure to solve it.The composite structure is a structure that mixes two or more materials of different properties.The structure can make full use of the advantages of different materials and play the bigger role.Concrete-filled steel tube structure is common in practical engineering,but it also has many shortcomings because of its own characteristics,we should explore other materials to improve the concrete-filled steel tube structure.CFRP is a kind of microcrystalline graphite material which is prepared by carbonization and graphitization of organic fibers.The specific strength and specific modulus of CFRP are large and it has good corrosion resistance and designability.Therefore,the combination of CFRP materials and concrete-filled steel tube structure can not only reduce the steel consumption and engineering cost,but also prevent the steel tube from being corroded and increase the service life of the structure.In this project,the flexural torsional hysteretic behavior of square section and circular section CFRP concrete-filled steel tube will be studied.Each group of the test is set up with 9specimens,a total of 18 specimens;Then three parameters are set,moment ratio,longitudinal carbon fiber layer number and transverse carbon fiber layer number,to analyze the test results and various indicators of the specimens;Finally,two different sections are compared,the conclusions are as follows:1.For square section and circular section specimens,it decreases with the increase of moment ratio,and also increases with the increase of transverse CFRP layers.However,under the influence of the number of transverse CFRP layers,the maximum increase of the bearing capacity of the specimen is located in the load-bearing area.For the square section specimen,the maximum difference of the increase is located in the tension area,which is about 10.9%,while for the circular section specimen,the maximum increase is located in the compression area,which is about 8.9%.The influence of the number of longitudinal CFRP layers on the specimens with different sections is different: for the square section specimens,the influence on the bearing capacity of the specimens is more obvious when the rise tends to be gentle in the later stage of the test,and the bearing capacity decreases with the increase of the number of longitudinal CFRP layers,and the maximum decrease is in the compression zone,which decreases by about 8.8%;for the circular section specimens,the bearing capacity of the specimens is also affected when the rise tends to be gentle in the later stage of the test However,the bearing capacity increases with the increase of the number of layers,and the maximum increase is in the tensile zone,which increases by 6.5%.2.For square section specimens,regardless of the bending moment ratio m,the three direction strains are hysteretic curves,that is,the tension and compression of the specimens occur alternately;For circular section specimens,regardless of the bending moment ratio m,the 45 ° direction tension and compression of the steel tube occur alternately,the transverse direction of the steel tube is always in tension,and the longitudinal direction of the steel tube is sometimes only in compression,and sometimes in tension and compression.3.For square and circular section specimens,CFRP can delay the tube buckling and improve the ductility.4.For the square section specimens,when the moment ratio increases,the stiffness decreases and then increases.CFRP layers have no effect on the stiffness;For the circular section specimens,when the moment ratio increases,the stiffness increases and then decreases.The stiffness also increases when the number of transverse CFRP layers increases,at the same time,longitudinal CFRP layers affect the stiffness too. |
