Study On Fatigue Behavior Of Partially Prestressed Concrete Beams With HRB600 Grade Steels

HRB600 grade steel enjoys a lot of advantages, such as good ductility and high strengt h. It was applied in many cons truct ion proj ects as a new reinforcement ma terial in foreign count ries. I n China, most experimental s tudie s focused on the configur ati on of HRB500 grade steel in reinforced concrete str ucture. The application of HRB600high-strength stee l a nd experimental st udy on i t were st ill in t he i nitial stage, while t he study on applying HRB600 grade steel a s non-prestressed re inforcement of partially prestressed conc r ete beams is still bl ank.The experime nt produced a total of four test beams, two of which were used t o do static load test, the other t wo of which we re used to do fatigue test. The cha nge characteristic s of HRB 600 grade st eel in partially prestressed concrete beam we re analyzed.Other after fatigue loading changes in char acteristics of pres tressed concret e beams cracking degre e, carrying capacity, c oncret e, non-prestressed tendons, strand and deflection were also analyzed.Experiment al studies shows: The number of cracks and beam deformation of experimental beams in static load damage test aft er c yclic loading was gre ater tha n those in static loa d damage test without cyclic loading; after prestressing was put in the tension zone of bea m, the neutral axi s of beam fell down, and the neutral axis of test beam moved up with t he effect of cyclic loading. This is bec ause under t he load effect, stra in changes of concrete in compression zone are smal ler than the strain changes of non-prestres sed te ndons a nd tendons in tension zone. Whether t est beams was pre-spl it or not before cyclic loa ding, the movement of neut ral axi s of beam was very small after cycl ic loading and ther e was still prestressed in test beams, whic h indi cat ing that the fat igue resistance of prestressed concrete beams is very well. Both theoretical ana lysis a nd real phenomena proved that t here was no fatigue damage happened i n the concrete in compression zone,HRB600 grade steel and pre str essi ng strand after 2 million l oad cycles.