Research On Long-Term Deformation Of Long Span Rigid Frame-Continuous Bridge

With the development of transportation, the construction techniques and scale of long span concrete beam bridge in China have been reached to advanced levels in the world. With the age increasing, many concrete girder bridges are suffered from main girder extensive cracking and excessive vertical deflections in the mid-span, which seriously influence the operation safety and service life of the bridge.Relying on National High-Tech Research and Development Program (863 Program) of long-term deformation and cracking-control technology of the long-span concrete bridges, the main factors influencing deformation of rigid frame-continuous box-girder bridge are researched in this paper. The main works and results are shown as follows:(1) The foreign and domestic developments of prestressed concrete rigid frame-continuous box-girder bridge are researched, and the common disease and its influencing factors of long span concrete beam bridge are discussed in this paper.(2) Taking Dongming Yellow-River Bridge as a calculation example, a space model of long span prestressed concrete rigid frame-continuous bridge is established by using finite element analysis (FEA) method. The influence of vertical prestressing loss, shrinkage and creep of concrete, temperature change and unequal settlement of pier on this bridge is analyzed. The analysis results indicate that:The more vertical prestressing loss, the bigger deflection grows. In addition, the influence of vertical prestressing loss of top slab on long-term deformation is more obvious than the one of bottom plate; The shrinkage and creep of concrete is the major cause to long-term deformation of bridge, which is also influenced by environment relative humidity and loading-age greatly; The effect of overall temperature change on structural alignment is tiny, but the influence of unequal settlement of pier on the bridge should not be ignored.(3) To research the fatigue damage of rigid frame-continuous bridge under vehicle load, the fatigue test to prestressed concrete bridge is taken in laborary. Based on the test data, the fatigue damage of prestressed concrete structure and stiffness reduction of prestressed concrete bridge under the reaction of repeated load are analyzed. Applying the test results on Dongming Yellow-River Bridge, the influence of stiffness reduction on long-term deformation of main girder is discussed. The degree of the influence of various factors to the bridge deflection is also discussed(4) Based on the analysis of this paper, some suggestions are proposed to reduce the long-term deformation of rigid frame-continuous box-girder bridge.