Analysis And Research On The Shrinkage, Creep And Settlement Influence In Old Bridge Rebuilding Projects

With the development of China's infrastructure and transportation industry, there will be an increasing number of bridge rebuilding projects. Our current and future tasks are rebuilding old dangerous bridges to restore or improve their carrying capacity and ensure the transportation safety.This paper explores some problems in widening bridges, such as the concrete shrinkage and creep, the horizontal connection and the settlement difference. Some rules are summarized to provide as references for the future research in this area. This paper includes:(1) The analysis of common methods, which are used in bridge widening, shows that if it is bilateral widening, usually the upper structure is splicing, substructure is not connected to make joints in bridge deck formation; for unilateral widening bridges, generally, a new bridge is parallel built to the existing bridge;(2) Based on the comparative analysis of various patterns of concrete shrinkage and creep, such as CEB-FIP, ACI209, BP, GZ (1993) and GL2000, here comes various applied conditions.(3) After doing the analogue computation of hollow slab bridges, t-shaped bridges and box-type bridges by using finite element software(Midas Civil), results show that, due to different concrete shrinkage and creep paces of old and new bridges, which will produce huge additional internal forces at edge beams and connections of the new and old bridges, while the remaining main beams produce smaller additional internal forces. In view of the above issues, this paper raises some solutions, such as delaying the placement time of new and old bridge connections, the usage of high-performance materials to improve the structure of the force.(4) Through the research on prestressed concrete beams in case studies, results show that the changes of creep deflection are more sensitive to the surrounding environment. The deflection will increase with lower humidity and vice versa.(5) After doing analysis and calculation on the t-beam bridge by using Midas Civil software, this paper proposes measures to control the settlement difference, such as applying smaller settlement of pile foundation to the widening part of the new bridge, delaying time on pouring new and old bridge joints and limiting the poured settlement in 5mm to reduce the settlement difference of old and new bridges.(6) The above research results are applied to the bridge widening design project in Beijing to Shijiazhuang segment of the extension of Beijing, Hong Kong and Macao.