Research On Axial Compression Performance Of Steel Reinforced Recycled Concrete Columns Of Restrained By CFRP Strips

In recent years,China's construction industry has shown a high-speed development trend.With the development of buildings,a large amount of construction waste is produced.These building wastes are buried and stacked at will.At the same time,as one of the important building materials,concrete materials are also widely used,resulting in a large number of natural resources being exploited.On the one hand,the research and application of recycled aggregate concrete materials solve the problems of pollution and destruction of ecological environment caused by construction waste.On the other hand,it reduces the consumption of non renewable resources to a certain extent,which is of great significance to the strategy of building an environment-friendly society and realizing sustainable development in China.In addition,carbon fiber reinforced polymer(CFRP)is a new material for structural strengthening,which has the advantages of high strength,lightweight,good corrosion resistance and durability,and is widely used in engineering construction.In this paper,a new type of steel reinforced recycled concrete columns restrained by CFRP strips is proposed,which is not only green and environmental protection,but also has the advantages of high bearing capacity and good ductility of steel reinforced recycled concrete composite columns.In addition,the existence of CFRP strips makes the internal recycled concrete in three-dimensional stress state when it is subjected to axial load,which delays the compression and bending of internal steel,and further improve the bearing capacity and deformation capacity.Therefore,it is necessary to carry out experimental research and theoretical analysis on this kind of structure.In this test,nine steel reinforced recycled concrete columns are taken as the foundation specimens,and two layers of CFRP carbon fiber strips are wrapped outside the columns to form the specimens of the steel reinforced recycled concrete columns restrained by CFRP strips.It is tested under axial compression.The effects of the test parameters such as the replacement ratio of recycled coarse aggregate,strip spacing,strip width and recycled concrete strength on the axial compression properties of the specimens were studied.Through the test,the failure process and failure mode of the specimen under the axial load are observed,and the load displacement curve,the load strain curve of each part,the transverse deformation coefficient curve and the performance indexes of the specimen are obtained.The influence of recycled coarse aggregate replacement rate,strip spacing,strip width and recycled concrete strength on the axial compression performance of specimens is mainly analyzed.The results show that the failure modes of recycled concrete columns confined by CFRP strips under axial compression are almost the same.The section steel first reaches the yield state,then the longitudinal bars and stirrups yield one after another,the recycled concrete is crushed,and the transverse deformation of the specimen is intensified.Finally,the CFRP carbon fiber strip was broken,resulting in the loss of the bearing capacity of the specimens and declared to be damaged,which was brittle.At last,on the basis of the test,the bearing capacity of the specimens under axial compression was calculated by using the unified strength theory and the formula in the relevant American codes.And the two calculated values are compared with the test values.The results show that the two results are in good agreement and the error is small.The above conclusions can provide a theoretical reference for the engineering application of the axial compression columns.