The Study On Design Method Of Prestressed Tendon Layout Of Long-span Prestressed Concrete Continuous Rigid Frame Bridge

The box girder bridge constructed by cantilever method has many advantages such as large spanning capacity and good comprehensive performances.In recent years,it has become the main type of bridge spanning rivers.However,with the increase in operating hours,many large-span continuous rigid-frame bridges have experienced problems with large mid-span down warping deflection.Therefore,this paper focuses on the design of the bundle design method of large-span continuous rigid-frame bridges which aims at reducing the mid-span deflection.(1)This paper demonstrates the problems and research status of prestressed concrete continuous rigid frame bridge at home and abroad,and summarizes and analyzes the development course and development trend of continuous rigid frame bridge;(2)This paper summarizes the current methods and research status of continuous rigid frame bridge design research.In accordance with this,a series of practical methods to design the box girder bridge longitudinal prestress distribution bundles is proposed.The method is designed to enable the design of prestressed concrete bridges to achieve load balancing and to meet design specifications.(3)By using the theoretical derivation and numerical simulation of the finite element software,the relationship between the tension length of the longitudinal backplane bundles and the mid-span bending moment is demonstrated,and the conclusion is drawn that the span length of the mid-span backplane bundles should not exceed half of the mid-span span length.A distribution design method for the backplane bundle is proposed.(4)Based on the "zero load moment method with dead load",the design method of three groups of bundles for the roof plate is proposed.By design of fitting distribution bundles for multiple bridges,the design effect of reducing the mid-span deflection can be achieved.In addition,after the statistical analysis of pectoral plate of several bridges,the design principles of pectoral plate bundles is determined,and a simple design method for pectoral plate bundles is developed.(5)By using the “feasible region” to make targeted adjustments to the initial bundles,an iterative method of adjusting only the backplane bundles and an iterative method of simultaneously adjusting the backplane bundle and the roof bundle are proposed.(6)The proposed bundle design method is used for trial bundle design,and the design status of the bridge is reasonable and the mid-span deflection is small.Therefore,it is verified that the bundle design proposed in this paper is a simple and practical design method.(7)Further study is made on the effects of roof bundle,mid-span backplane bundles,and side-span backplane bundles on the deflection of the bridge,cross-middle section stress,and fulcrum section stress,and the contrastive analysis is made to the design effect of replacing the backplane with external bundles and hybrid bundles.In addition,the influence of side-span backplane bundles on the mid-span deflection is discussed as well.In this dissertation,the research results can provide the bridge design with practical reference.