Reserch On Disease And External Prestressing Reinforcement Technology For Concrete Bridges

In this paper,for a concrete beam bridge in Tianjin as a engineering example, itsdiseases was analyzed，and the technical condition of ssuperstructuree and bridgedeck system of bridge were evaluated. According to date measured and calculationmodel of MIDAS Civil,natural frequency of beam was evaluated.Based on the bridge detecting data, the bridge check coefficient,bearing capacitydeterioration coefficient； the cross-section reduction coefficient and Vehicle loadcorrection coefficient were considered, the structural resistance effect and load effectwere respectively corrected in limit state equations，The calculation results show thatmain beams meet the requirements of the original design load.For older concrete beam bridge in service, During to the influence of load，temperature and other factors,early concrete bridges constructed could occur withdifferent levels of damages and diseases. The bridge bearing capacity can not meetthe current specification requirements. Reinforcing old concrete bridges withexternal prestressing could improve performance and increase the carrying capacity.When old concrete bridge was reinforced by external prestressing, loadingreinforcement had been existed. In its design calculations, the biggest differencebetween newly-built and reinforcing old concrete bridges is that the impact of theforce on different stages should be considered. On the basis of the principle of forcemethod, the stress-increment in normal section bearing capacity formula waseducated for external prestressing tendon without turning point. The calculatingmethods of crack resistance were put forward on different stages. Externalprestressing reinforcement design was given. The technical characteristics andapplications of external prestressing reinforcement were described in prestressingsteel material properties performance and related conditions.Comparing external prestressing reinforcement plan with girder replacement plan in projectcost and traffic period interrupted,external prestressing reinforcement plan was recommended.This paper is valuable in carrying capacity of old bridges and design and construction ofconcrete beam bridge reinforced by external prestressing.