The Study On The External Prestressing Applied On The Reinforced Concrete Continuous Curved Girder Bridge

With the rapid development of Chinese national economy, the flyovers andviaducts play more important roles in cities. The significance of curved girder bridge,which is an important part of them, has gradually been acknowledged by the bridgeengineers. The construction of curved girder bridge has been more than30years ofhistory in China. With the increment of the bridge’s service period, the diseases ofconcrete curved girder bridges have been reflected gradually. The mechanicalcharacteristics of curved girder bridge are different from the characteristics of ordinarystraight girder bridge. Therefore, this paper starts from the mechanical characteristics ofcurved girder bridge to analyze the main diseases of curved girder bridge and its causesand to explore the effects of external prestressing technique on mechanicalcharacteristics. The paper has completed the following aspects of content:In accordance with the actual conditions of the background bridge,the paperestablishes bridge finite element model to analyze the distribution characteristics of theinternal force, deformation and stress of each main girder under the gravity action.Under the gravity, for the curved girder bridge with the same girder cross section, thebending moment, deformation and support pressure of outside girders are larger thaninside ones. In certain cases, the inside supports may be under tensile forces, whichshould be taken into consider both in design and construction.In view of the diseases of the background bridge, the paper analyzes the reasons ofdiseases by finite element software. The results show that, under the temperature loadeffect, the failure of limited blocks leads to the thing that the main girders cannot free tomove both in the longitudinal and transverse directions, which causes large stresses andmany fractures on the bottom of the girders.The determination of ultimate bearing capacity is the key to the externalprestressing technique, which based on the ultimate stress increment of externalprestressed tendons. By comparing the stipulate of the ultimate bearing capacity indifferent countries and combined with the actual characteristics of curved girder bridge,this paper educes the modified formula of ultimate bearing capacity in the curved girderbridge and extends it to the condition of using one or two deviators.This paper uses finite element model to analyze the effects of external prestressing on mechanical characteristics of curved girder bridge and reaches the conclusion thatexternal prestressing has the capacity to decrease the midspan bending moment anddeformation, to reduce the bending moment at the top of the piles and to cause largestresses on the bottom of the girders.In the end, by comparing the influence of setting different deviator number, thispaper comes to the conclusion that larger quantity of the deviators means the externalprestressed tendons are more close to the line shape of the girder and the effects ofexternal prestressed tendons are greater.But its structure is more complex.