| The unbonded partially prestressed concrete (UPC) is an important branch of post-tensioned structure and its construction of simple and quick, good mechanical properties, significant economic benefits, etc. has been recognized. With mature production technology of high-strength materials, applied high-strength steels to UPC is bound to be a trend. At present, experimental and theoretical analysis of UPC beams with high-strength steels under fatigue condition is no one in the study.This test produced four UPC beams with same size which are divided into two groups, and each group produced two identical beams. Each group has one beam to do the fatigue test, the other to do static destruction test, and both for comparison. this article has done the following work.1. The status of fatigue test research of the existing partially prestressed concrete structure (bonded and unbonded structure) has been systematic analyzed. At the same time, summarized and compared the fatigue characteristics.2. Fatigue test on two beams and static destruction test on the other two beams are made. During the experiment, observed cracks and measuring deflection, concrete section strain, steel strain and strand internal forces. Comparative analysis on the law of crack, deflection, strain of concrete at compression zone, strain of steel at tensile zone and internal forces of steel strand.3. UPC beam fatigue residual deflection and deflection calculation formula were deduced with test data.The study indicates the followings:The nature of the force of UPC beams with high-strength steels is reliable and its test phenomenon is similar to UPC beams with ordinary strength steels. Bearing capacity of beams decreased by 12.9% after repeating loading test. Dynamic effect must be considered under repeating loading. Calculation formula of the short-term stiffness under dead load still uses the formula in procedure. The fitting formula of residual deflection and deflection is compatible with real conditions. |
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