Study On Control Criterion Of Differential Foundation Settlement And Comparison And Selection Of Transverse Connection Structure Of Prefabricated Box Girder Widen

This paper is based on the project ‘Study on the Safety Assessment and the Key Technology of the Assembled Box Girder Based on Cracking Damage',which is a traffic construction science and technology project from Shanxi Province.Adopting an in-depth research on selection of transverse connection,control standard of foundation settlement,and so on which questions encountered fabricated box girder bridge widening in Long Han highway reconstruction project by combining testing on site,literature review and numerical analysis.The main work and achievements as follows:(1)Summarized in detail transverse connection mode and structural form between girder which be applied to broaden small fabricated box girder bridge,and systematically analyzed their advantages and disadvantages.It settle the basis for the go-on study.(2)The influence of different connection modes on the force of hybrid structure after widening of bridge is studied.The result shows that different transverse connection such as hinge,semi-rigid connection,weak rigid connection,strong rigid connection,has little effect on the internal forces and deflection caused by live load.However,it greatly reduces the internal force and deflection of the boundary beam of old bridge.From the contribution of the transverse connection to the force of the old bridge,the connection of the strong rigid connection mode is the biggest,and the hinge connection mode has the least influence.(3)The influence of different connection modes on the splice position and the stress of the main beam caused by uneven settlement of the old and new bridge foundation and the control standard of settlement difference between the old and new bridge foundation are studied.The results show that the strong rigid connection is not conducive to the force of the main girder,but the semi-rigid connection and the hinge connection is not conducive to the force of the splicing part.We recommend using weak rigid connection to broaden the assembly type box girder.Based on the performance of superstructure,this paper proposes that the standard value of settlement difference between old and new bridges under the weak rigid connection widening mode is 5mm.(4)The settlement monitoring of pier in construction stage before and after new and old bridge splicing is carried out,and the grey model is used to predict the settlement law of spliced pier.The results show that the settlement of each pier is stable after one month,and the average accumulative settlement is not more than 1mm.The final predicted settlement value of the pier after 6 months is within the control standard of the settlement difference between the old and new bridges proposed by the finite element analysis.