Modeling And Analysis Of Mechanical Behaviour Of Bridge Structure Bending Strengthened With FRP

Concrete cracking of highway girder bridges is a poluar problem. As a result,repair/strengthening of such bridges with cracks has become a hot research topic in thebridge strengthening field. Due to the advantages of fiber reinforced polymer (FRP)material, FRP have found increased applications in bridge structures in recent years.Among different strengthening techniques, externally bonding (EB) FRP to the concretesurface is the most common application. Existing studies have showed that EB FRP cannot only enhance the strength of the concrete structure but also increase its stiffness. Theeffectiveness of EB FRP system is largely dependent on the FRP-to-concrete bondedinterface (interface), thus, accurate simulation of the behaviors of the interface is a keyissue for a bettern understanding of the behaviors of the FRP strengthened structures.Against the above background, the study presented in this thesis aims to investigate thethe behaviors of RC bridge structures flexually strengthened by FRPs, based on thekNowledge obtained from existing studies. The main contents covered by this thesisinclude:Firstly, FE analyses were conducted for the published standard highway I-level8mcored slab bridge structure (released by the Ministry of Communications of China) withand without EB FRP. The numerical results showed the FE model used is capable ofaccurately modeling of the behavior of the bridges structures with and without FRPstrenghtening. Secondly, the verified finite element modeling approach was then used tosimulate the behaviors of one prestressed continuous box girder with and without FRPstrenghening. Based on the numerical results merits and demerits of the strengtheningmethod were summarized, based on which some valuable suggestions were proposed forthe actual application of FRP in such type of bridge.The results presented in this thesis showed that EB FRP is very effective in theflexural strengthening of bridge structures, especially in enhancing the ultimateload-carrying capacity of the bridge. It was also found that concrete compressive failure isa typical failure mode for the bridge structure strengthened with FRP; in such acircumstance, the strength of FRP material has little effect on the strengthening effect. Asa result, the optimized use of FRP in strengthening is an important issue to be explored asthe utilization ratio of FRP materials will be reduced when large amount of FRPs areinappropriately used. The results of pre-stressed continuous box girder showed that effectof the FRP strengthening is rather limited as assessed by the stress level, and thestrengthening effect of FRP is significantly increased when pre-stressed, showing thatpre-stressed FRP may have a broader application in strengthening bridge structurres.