The Research On Nanjing Shijiu Bridge Upper Structure Reinforcing Design

Since the reform and opening up, our country fruits in the field of bridgeconstruction. However, with the new engineering construction, a lot of old bridgesare in urgent need of strengthening at the same time, especially in some low gradehighway. A large number of small and medium span bridges lack bearing capacitycaused by a lack of design load and lack of maintenance. Therefore, if we can find asuitable reinforcement for small and medium span bridges, we can not only save alot of investment, make effective use of resources, but also obtain better socialbenefit.The paper taking Nanjing Shijiu bridge as an example, do some research on thethe bridge upper structure reinforcement. The main content includes:1, discusseshow to carry on the appraisal of old bridge bearing capacity;2, use Midas civilsoftware to calculate the old bridge reinforcement target;3, the reinforcement designfor Nanjing stone bridge is based on specifications for design of highway bridgesreinforcement, using the method of enlarged cross section, pasting steel plate,pasting carbon fiber and applying external prestressing;4, the reinforcement effect issimulated with ANSYS software;5, using the value engineering to analysis thereinforcement scheme, considering the construction cost, closed transportation costs,maintenance costs, and find the most valuable reinforcement scheme.Finally, the paper gives the conclusion:1, Enlarged cross section methodincrease the coefficient of bearing capacity, and the construction cost andmaintenance cost is the lowest, when traffic is not big that we cannot consider closedtraffic impact, increasing section method would be a most valuable method ofreinforcement;2, Pasting steel plate method would be taken into account when thetraffic must be closed in the medium and small span beam system bridgereinforcement at present. Pasting steel plate method is one of the most valuablereinforcement method, and the construction technology is easy to promote.3,Pasting carbon fibre. Its construction cost is higher, but the later maintenance cost isless. When we need to close the traffic, it is also a kind of convenient method. Whatis insufficient is that its own strength cannot be obtained to give full play and the increasement of bearing capacity is limited. If prestress can be added into carbonfiber, this method can greatly improve the bearing capacity of the structure. It will bethe most valuable reinforcing method.4, External prestressing reinforcement bychanging the original structure stress system, can greatly enhance the structurebearing capacity, and the maintenance costs less than pasting steel plate method. Thereinforcement method is also a kind of high deficiency method in the bridge ifmaterial strength demand is suitable. There will be a lot of stress concentration in theanchor plate and steering block position. Local damage may occur and cause thestructure damage. For the bridge which is in a good keep, external prestressreinforcement will be comparable to pasting steel plate method.5, With thedevelopment of science and technology, the optimal reinforcement scheme for smalland medium span bridges will be constantly changing. But, we can still analysis themethod for concrete bridge reinforcement case through the value engineering, andfind a best-value reinforcement scheme.