Study On Stress Behavior Of Unbonded Partially Prestressed Beams With 600MPa Steel Bars

600MPa steel bar,which is a new type of high strength steel bar,has good mechanical properties.Under the same situation of bending capability,steel bar's dosage can be reduced by using 600 MPa steel bar,which has good economical and social benefits.Adding high strength steel bar into ordinary concrete beam may lead to the component crack too wide and excessive deflection.Unbonded partially prestressed structure can postpone the crack appear and reduce the deflection of structure.Therefore,it is necessary to study the application of 600 MPa steel bar in this structure.In this paper,five unbonded partially prestressed concrete beams are tested to study the the influence of non-prestressed reinforcement ratio and strength of concrete on mechanical properties of tested beam.This thesis analyzes the prestressed loss,ultimate stress increment cross-sectioanl crack resistance,normal section bending bearing capacity,crack,deflection,and ultimate stress increment of tested beam.It also uses ANSYS finite element software to make the nonlinear analysis of tested beam,and then uses calculate results to verify the test results.The results show that increasing the non-prestressed reinforcement ratio can reduce the crack resistance and ultimate stress increment of tested beam,and improve its bending property;Increasing the strength of concrete can improve the crack resistance,bending property and ultimate stress increment of tested beam;The prestressed loss,cracking moment,ultimate flexural strength,crack spacing,maximum crack width and stiffness before cracking of unbonded partial prestressed concrete beams with 600 MPa steel bar can be calculated by the formula in GB50010-2010;ANSYS finite element method can simulate cracking load and ultimate load of tested beam accurately.It also can effectively simulate the deflection and the stress of presstressed steel's changing situation of tested beam,which under the action of three points load.