Nonlinear Analysis Of PC Box Girder Strengthened By External Prestressing

In the process of bridge operation, a lar ge number of bridges m ore or less appears different degrees of disease. It has serious influence on the safety and durability of bridges,so they need to be reinforced. This m ethod is put external prestressing tendons outside the bridge’s body, tendons anchor firmly in bridge beam two ends, and exert axial pressure and curve to beam to offset part of the internal force produced by the loading,thus im prove the stress state and bearing capacityof structure,crack resistance and reduce the deformation.This article mainly carried on the following work:(1)From the design, construction and operation management and other aspects to analyze the causes of diseases of the curr ent bridges, comparing the advan tages and disadvantages of the commonly used reinforcement techniques.(2)Researched on th e basic principle of external prestressing reinforcement, the internal force of the structure and the calcu lation formula of stress increm ent. From the cross-section balance, the overall coordination of deform ation deduced the external prestressing tendons stress increment formula.(3)The study was carried out in further inve stigation of the sim ply supported box beam strengthened by external prestressing through thirteen three-dim ensional finite element model established by Midas FEA. Exte rnal prestressing reinforcement process is simulated by constru ction stage for nonlinear analysis. Researched and analyzed on the effect of depth-span ratio, comprehensive reinforcement ratio, the tension control stress and other factors on the force performance bearing capacity, deflection and crack extension.(4)Combining theory with practice in this paper, a four span continuous box girder bridge is reinforced by external prestressing and presents the desi gn idea and the m ain processes of calculation. According to th e principle of equivalent rigidity, it can be transformed to be a simply supported beam bridge with the same span. The m echanical properties, the deform ation behavior and the crack extension of the box beam was compared before and after reinfo rcement. The practical exam ple illustrates external prestressing reinforcement technology can achieve the desired effect,which can be used for reference in similar projects.