Influence Of Temperature Effects And Shrinkage-creep For Long-span Continuous Rigid Frame Bridges

In recent years, many economical, reasonable, artistic bridge structures haveappeared with the rapid development of bridge construction in our country. Because ofits linear and liveliness, convenient construction, high strength and strong spanningability, long-span continuous rigid frame bridge with high piers is favored by designers,and is applied widely recently.Under the action of temperature load and creep shrinkage of concrete, long-spancontinuous rigid frame bridge will produce grea t internal force, which may lead cracksor large deformation and reduce the service life of the concrete structure, so thetemperature effect of long-span continuous rigid frame bridge and creep shrinkage ofconcrete have aroused great attention in the circle of engineering.Take Niujiaoping Two-line Super Bridge as an example, this essay conducts analysis of temperature effect and creep shrinkage effect on bridge according to Midas/Civil (2010).The selection of calculation scheme and various parameter values reflect the actualsituation of the bridge as far as possible, in order to get a more accurate simulative results. Main work done is as follows:①Analyzed the characteristics, classification and distribution of the temperature load of the concrete, and gave a simple introduction to calculation method of temperature load and temperature stress of box girder of concrete.②Drew up temperature gradient curve which can reflect the change of bridge temperature according to the measured temperature data and made comparative analysis ofseveral temperature gradient modes in common use at home and abroad, calculated the stress and deformation of the bridge’s structure and probed the influence of various temperature model on the structure, computed and analyzed the stress and deformation of bridge’s structure under the action of various temperature system and gradient in the condition of different sunlight and cold wave.③In view of the project of Niujiaoping Two-line Super Bridge, find the bettertemperature gradient curve which are suitable for the southwest region by way of comparing the difference between the temperature gradient modes calculated in accordancewith the Rules and Regulations of China Railway and according to the measured temperature data.④Analyzed the mechanism of the shrinkage and creep of concrete,and summarized the calculation methods of several kinds of creep and shrinkagemodels,then discussed the relative humidity, concrete strength and the influences offactors such as theoretical thickness of member on the creep and shrinkage coefficientof three types of creep and shrinkage prediction model–CEB-FIP78,CEB-FIP90andACI209(92),then introduced the influence law of various factors on the creep andshrinkage coefficient of bridge structure.⑤By comparing the deflection value and stress value of the Niujiaoping bridge inoperation stage calculated by CEB-FIP78, CEB-FIP90and ACI209(92) three types ofcreep and shrinkage prediction model with measured values, fond out the model whichis most close to the measured data, namely the CEB-FIP90model; then analyzed theshrinkage and creep effect of bridge structure by CEB-FIP90model, and summarizedthe laws of the its effect on the deflection, internal force and stress of the bridge.⑥Respectively researched the influence of temperature on shrinkage effect andcreep effect of long-span prestressed concrete rigid-frame bridge, and preliminarydiscussed the coupling effect of temperature effect and shrinkage and creep effect.