Abstract:

In order to effetively detect the tension of vertical prestressing bars to improve the construction quality and to solve the engineering problem of the cracking at box girder webs caused by vertical excessive prestress loss, the exposed section of fine rolled twisted bar was assumed as a cantilever beam based on the dynamic theory, and the anchoring section of vertical prestressed steel was simulated by one rigid arm and two elastic supports. Then, the plane elastic supporting model was established. The nonlinear model between tension P of fine rolled twisted bar and elastic support stiffness K was put forth based on the experiment data of this model. The proposed method was verified by model test and a method based on flexural rigidity of the exposed segment in the anchorage zone, and this method was applied in the actual bridge engineering. The nondestructive detection method of vertical prestressing was used at the construction period of box girders, the qualified rate of vertical prestress increased from 58.0％ to 96.8％, and the construction quality of vertical prestressing was effectively improved. Based on this research, the engineering measures were proposed to improve the anchor plate mounting precision.

Key words: box girder, fine rolled twisted bar, vertical prestressing, plane elastic supporting model, model test, nonlinear, non-destructive test, anchor plate