Study On Stress Behavior Of Unbonded Partially Prestressed Concrete Beams With HRB500 Steel Bars

Unbonded prestressing concrete (UPC) beam has the advantages of simple construction technology, excellent structure and easy maintainance. However, its application is limited duo to its lower ultimate bearing capacity from self structure performance. As one type of new brand steels with good performance, the rebar Graded HRB500 will be used to improve the capacity of UPC beam. That is the emphasis discussed in this paper.Through testing the flexural behavior of five experimental beams (non-prestressed reinforcement beams with HRB500 and normal), the paper mainly consider the influence non-prestressed longitudinal reinforcement strength and reinforcement ratio cause on the bending capacity, prestressed reinforcement ultimate stress increment, ultimate bearing capacity, development rule of deflection, cross-section crack resistance and crack spacing. It also check the applicability according to the test result and formula defined in the code.The results show that HRB500 non-prestressed reinforcement can significantly improve not only the increment of ultimate bearing capacity but also the normal section's bending resistance of UPC beams; When yield strength of HRB500 rebar is 450Mpa, it's checked that the emergency capacity is enough under the present code. There is a linear relation between limit stress of rebars used in UPC and mid-span deflection. We can derive the proposed formula for calculating the increment of limit stress from the fitted formula.