Abstract: By simulating different floating curve radiuses of the prestressing forces way,the experiment on spalling stress is done with six experimental beams.The analysis shows that the main factors which influence the spalling stress are as follows:the stressing force of prestressing bundle,the curve radiuses of the way,the structural rigidity of the center line of the way and etc.The results of the experiments show that the deterioration curve of the balks basically coincides with the center line of the bellows.