Experimental Study On Mechanical Properties Of Cylinders Circularizing From Square Columns That Wrapped With CFRP

Fiber reinforce polymer(FRP)has the advantages of light weight,high strength,corrosion resistance,and is widely used in civil engineering.Both results of the domestic and foreign scholars' prove that FRP reinforcing concrete structures have superior performance.Square columns has been widely used for its economy,shear performance and easy to be hide.With the development of urbanization and urban renewal,some of the original buildings rebuild.In order to avoid wasting,most of buildings continue to be used after different ways of strengthening,using carbon fiber cloth material reinforced beams bearing component is one of the most effective way of strengthening.When constraining square columns by steel or FRP materials,only some areas are effectively confined,and easily destroyed in the corner due to stress concentration.For easing the stress concentration degree,people adopt civilizing before reinforcing.Relative to the FRP constraint columns,the effect of constrain is still not as good as circular cross section column for its uniform constraints.In consideration of the mechanical property of arc treatment columns,this paper studies the effect of different space of CFRP stripe and different strength of concrete to strengthening columns that circularizing from square columns,and searches the size effect of arc treatment columns.This paper includes two parts,mechanical properties and size effect of circularizing columns.In the study of mechanical properties,stress mechanism of columns wrapped with CFRP was investigated.Based on the cylinders that were circularized by C30 and C60 concrete from square columns,stress-strain curves obtained,effects of layers of CFRP and concrete strength in the space of 30mm,45mm,90mm..In order to compare the bearing capacity of square and circular arc column that wrapped with CFRP,this paper gives out the residual bearing capacity Ps,which surplus after the deduction of the bearing capacity of surrounding four pieces of circular concrete bearing capacity by Peak stress PMax of arc treatment columns,namely Ps = PMax—PK.The experimental results showed that the value of Ps is bigger than the bearing capacity of related square columns'.Arc processing square column will help to improve the efficiency of strengthening.In the study of size effect of arc treatment columns,three sizes were conducted.Results showed that size effect were more obvious with the increase of the size and number of the parcel layer increased.Compared to the small size columns,when wrapped with two layers of CFRP,the big size arc treatment column's stress reduced up to 46%.