Cyclic Tests Of GFRP-Reinforced Crumb Rubber Concrete Columns

GFRP bars have good corrosion resistance that are used to replace steel bars to solve the durability problem of concrete structures caused by steel bar corrosion.However,GFRP bars are linear elastic materials without plastic energy dissipation,which results in poor ductility and energy dissipation capacity of GFRP reinforced concrete column.Crumb rubber concrete(CRC)is a new type of environmentalfriendly concrete material,which is made up of Portland cement concrete added with rubber particles,with good ductility and energy dissipation.The combination of CRC and GFRP bars is aimed to improve the low energy consumption and poor ductility of GFRP reinforced concrete column,which can further promote the application and development of FRP reinforced concrete structures.(1)Five groups of the CRC replacement percentage of 0%,5%,10%,15% and 20%were prepared by optimization of mix design and the related material properties were tested.The test results show that the rubber particles increase the peak strain and limit strain of concrete,and show better ductility and energy dissipation capacity;The calculation formula of parameter β values in Carreira-Chu constitutive model is modified that a variable considering the influence of rubber content on the constitutive model was added into the formula.(2)Completed full-scale pseudo-static test of seven GFRP reinforced ordinary concrete and rubber concrete columns,and all columns reach ultimate bearing capacity by the concrete in the compression zone is crushed without premature failure of GFRP bars.The test results show that using rubber concrete in GFRP reinforced concrete columns can improve the ductility and energy dissipation capacity of GFRP reinforced concrete columns.When the rubber content is 5% and 10%,the ductility coefficient increases by 51% and 87% respectively.Both increasing the reinforcement ratio and decreasing the stirrup spacing can improve the deformation capacity of the cloumns.(3)The finite element software OpenSees is used for model verification and parameter analysis of GFRP reinforced crumb rubber concrete columns.The results show that increasing the longitudinal reinforcement ration can improve the bearing capacity and deformation capacity of columns.By increasing concrete compressive strength,column bearing capacity can be improved,but the descending section of the skeleton curve will be steeper.By increasing axial load ratio(0.1～0.3),will reduce the column bearing capacity and deformation capacity.(4)Based on the calculation theory of ultimate bearing capacity of steel reinforced traditional concrete column,the formula of ultimate bearing capacity of GFRP reinforced CRC column is derived.It mainly includes considers the contribution of GFRP longitudinal bars in the compression zone,the modification of the parameters of CRC equivalent stress and the derivation of the limit reinforcement ratio,etc.The calculation formula is in good agreement with the test results.