Experimental Study On The Axial Compression Ratio’s Impact On Unbonded Partially Prestressed Concrete Column’s Seismic Performance

The earthquake is one of the natural disasters which has seriously bad effect on human’s lifeand property safety. After the earthquake,the structure or the specimen’s residual deformationdetermines its maintenance costs and technical difficulties, Configuration of unbondedprestressed steel strand in the concrete column can improve the structure’s displacementrestoring capacity, reduce the structural residual deformation after the earthquake. But at presentthere are limited studies on the comprehensive seismic performance of unbonded partialprestressed concrete column In the field of engineering,so this limits its application anddevelopment.The paper produced five tested columns, which are totally divided into two groups,thevariables of two groups are applied axial compression ratio and pre-axial compression ratio,analyses the impact of two variables on specimen’s crack development, the bearing capacityvalues(Cracking load, yield load and ultimate load),capacity degradation, stiffness degradation,ductility development, energy dissipation capacity, recovery performance, prestress loss andultimate stress increment,and based on the test data, ultimate stress increment calculationformula of every country’s norms has been checked.The research results show that:when the applied axial compression is small,throughincreasing applied axial compression ratio to a certain extents can delay the specimen crackingand yield, pre-axial compression ratio of the specimen has little effect on cracking load and yieldload; the column which has bigger applied axial compression ratio has high initial stiffness, but ithas poor ductility, small reset ability and small ultimate stress increment. the column’s energydissipation capacity can be significantly improved by increase applied axial compression ratio toa certain extent; the column which has bigger pre-axial compression ratio has high stiffness andultimate stress increment,but its energy dissipation capacity is small; pre-axial compression ratiohas little effect on the ductility; for stress increment assessment, it is proposed to use formula ofCanadian norms A23.3-94,or change related parameters of our country’s formula of norms“Technical specification for concrete structures prestressed with unbonded tendon”(JGJ/T92-93).