A Study On Application Of Three-dimensional Prestressed Concrete In Sheng Li Bridge

Nowadays, three-dimensional prestressed concrete successive box girders have been used for construction of highways, roads and streets in cities and railways since they have a number of key advantages such as strong integrity and rigidity, very little deformation, earthquake resistance, few expansion seams on surface of bridge and making driving comfortable, etc. The history of the use and development of three-dimensional prestressed concrete box girder techniques in China is still very short. It is of great significance to promote use of this new construction technology.The three-dimensional prestressed concrete box girder techniques is an advanced technology and there is difficulty of construction. This study discusses the key techniques of preventing over-length concrete cracks and provides references for promoting use of milled mineral powder by experiments in the Shengli Bridge Project on properties such as anti-permeability, carbonation resistance, freeze-thaw resistance, mechanical property and alkalinity of the high performance cement made up from milled mineral powder.At present there is not a complete set of specifications for the design and construction techniques of the three-dimensional prestressed concrete box girders. This study discourses the design principles of the three-dimensional prestressed steel on the basis of previous researches in combination with the features of Shengli Bridge; it analyzes the tension sequence and elongation of three-dimensional prestressed steels, strand pricking of over-length three-dimensional prestressed steel and construction difficulties of three-dimensional prestress tension; and it also proposes some key techniques and process of construction for the reference of construction project of the same kind.This study analyzes and studies causes of some defects in the building and using of prestressed concrete bridges, it points out that structure cracks beyond the permission of design represent defects of bridges, and analyzes some causes of cracks. Preventive measures against bridge cracks are discussed and suggestions on ways to deal with concrete cracks are also put forward.