Analysis Of The Influence Of Lateral Restraint On Prestressed Concrete Statically Indeterminate Structures

Prestressed technology is widely used in large-span statically indeterminate concrete structure. When tensioning prestressing tendons, because of the larger lateral stiffness, the vertical components (such as column, wall and so on) could generate lateral restraint for horizontal components. If the impact of lateral restraint was neglected, the theoretical analysis value of bearing capacity for horizontal components would be larger than the real ones, so it would lead to potential safety problems. Therefore, the analysis of lateral restraint for prestressed concrete statically indeterminate structure has great theoretical significance and application value.This paper firstly analyzes prestressing effect of statically indeterminate concrete structure, and shows the procedure block diagram of calculating loss of prestress based on the new code; then deduces the calculation formula of lateral restraint for statically indeterminate structure by two methods: One is according to deformation coordination conditions without considering the angle; the other is using the relevant knowledge of matrix displacement method and D value method, which neglect axial deformation and consider the angle of column ends. The paper deduces modulus of lateral restraint for one-storey & one-span structure, one-storey & double-span structure and one-span & double- storey structure respectively by the above two methods; at last the engineering project and the effect factors of lateral restraint for frame beam are simulated numerically by the finite element program SAP2000, the following conclusions are obtained:1. Through the numerical simulation results of lateral restraint for frame beam in engineering project, finite element numerical analysis results is close to theoretical calculation results, and closer to theoretical value by deformation coordination method, which suggests that the angle of column ends are very small, and because of which it can be neglected when calculating the influence of lateral restraint for statically indeterminate structure.2. Through the numerical simulation results of lateral restraint effect factors, the loss of lateral restraint for frame beam will increase gradually with the decreasing of linear stiffness ratio of beam to column, the increasing of span numbers of frame structure and the decreasing of eccentricity of prestressing tendons. Nevertheless, the pre-applied force has little effect on the loss of lateral restraint, and the order of tensioning prestressing tendons also has a certain impact on it.3. Through the finite element analysis,the paper proposed reducing loss of lateral restraint for statically indeterminate structure from four aspects, which include increasing linear stiffness ratio of beam to column, reducing span numbers of frame structure, choosing the order of tensioning prestressing tendons reasonably and conformation measures.