Spatial Effects And Web Stress States Of PC Box Girder Bridge By Cantilever Erection

Today, structural models with the plane frame elements are mainly used in the design and analysis of prestressed concrete box-girder bridges, but it cannot reflect the characteristics of spatial and local effects of this type of bridge. On the other hand, large general-purpose structure analysis programs for physical units (such as ANSYS), although characterized by its powerful functions and high versatility, can hardly perform analog computation such as prestressing, live load and concrete shrinkage and creep without secondary development when they are used to analyze prestressed concrete bridges. To overcome this shortcoming, Jiangsu Province Communication Planning and Design Institute has developed with years of efforts the "Refined Numerical Analysis System for PC Box Bridges" (abbreviated as RNAS-PCBB), which can be used to perform refined analysis of physical elements of prestressed concrete bridges with good effect.This paper, in conjunction with the core principle and application practice of the RNAS-PCBB, expounds the considerations in selecting the constitutive model of concrete and reinforcement in the analysis of prestressed concrete box-girder bridges, and discusses the analog method of prestressing in a 3D physical FE model using ANSYS and the 3D physical modeling method for prestressed concrete box-girder bridges.The paper, with prestressed concrete box-girder bridges as the objects of analysis and study, and using a project as an practical example, built a full-bridge space analysis model to perform stress state analysis for critical parts by taking into account such loading conditions as 3-direction prestressing actions. It discussed the shear lag effect at sections of different locations along the longitudinal direction of the bridge. In the model, consideration has been taken for the eccentric action of load on lanes and the varying laws of live load normal stress eccentric load coefficient in the longitudinal direction of the bridge. It has also analyzed the correlation of web bundle association form and stress distribution, and pointed out the important role of web vertical prestress and lower bending bundle in reducing the main tensile stress in the web. Finally, it studied the stress distribution of base plate and partial area of toothed plate under the action of prestressing force, and proposed the construction design provision to prevent cracking of the base plate and toothed plate in construction and in service. The research conclusions are of good application reference value in improving the design of prestressed concrete bridges.