Research On Temperature And Creep Effects Of Large-span Prestressed Concrete Bridges

When large-span prestressed concrete bridges are subjected to temperature load or concrete creep action, very large internal force will arose within the structure, and which will weaken the resist-cracking performance of its sections and temperature cracks can be produced. Thus, the safety and durability of the bridges may be seriously affected. The work based on the former researches, taking a typical three-span prestressed concrete rigid frame bridge and a prestressed concrete cable-stayed bridge as the background, the influence of temperature load and concrete creep on the bridge structure is analyzed.Based on heat transfer and FEM theory, the influence of temperature load and concrete hydration heat as well as its distribution on this type of bridges is researched and analyzed by adopting different models of temperature load in the codes of various countries. The results show that for prestressed concrete continuous bridges, the results obtained by the calculating modal in Chinese national code "General Code for design of Highway Bridges and Culverts" (JTG D60-2004) is more reasonable; fairly large tensile stresses will arose at the bottom of the girder because of temperature increasing, and it is even larger than the effects of live loads sometimes. Moreover, there is fairly large lateral tensile stress at the bottom of the top flange of box girder and some other members because of the nonlinearity of the temperature varing along the height and the spatial variation, similarly there is fairly large temperature stress at the cantilever flanges.The influence of concrete creep on bridge structure under the construction and operation stage for prestressed concrete continuous rigid frame bridge and cable-stayed bridge is also analyzed. Especially in the analysis of cable-stayed bridge, by comparing theoretical values with testing data, the computing formula in the code CEB-FIP is considered to be more ascendant in reflecting the influence of concrete creep on bridge structures. Some suggestions about the bridge health monitoring and assessment system are put forward.