The Reseach Of Hydration Heat Temperature Field And Crack On Rigid Frame Box Girder Bridge

In the process of concrete pouring will produce large amounts of the hydration heat.Because of the wide application of high strength concrete, and the large section area of thesegmental box grider near the main piers of long-span rigid frame bridge, so the size ofconcrete is larger than usual. Especially, the web, bottom plate and diaphragm plate of 0#segmental box grider will accumulate a large amount of hydration heat in the process ofconcrete pouring, lead to temperature inside the concrete structure is very high, but theexternal temperature is relatively low. So it forms a large temperature gradient, and theresulting temperature action will effect the box girder structure a lot, even cause thetemperature crack, and make long-term strength of concrete could not be guaranteed.In this paper, the research is based on main bridge of Dongguan Channel bridges,through measured the development of hydration heat temperature of 0# and 1# box gridersection, the hydration heat temperature field is imitated, analyzed and calculated by meansanalysis software MIDAS/Civil, based on this the temperature stress is forecasted. Thepaper’s specific works and research results are as follows:(1) In the construction process of 0# and 1# box grider section of main bridge,embedded the temperature sensor in concrete and collected a lot of temperature measurementdata, analyzed the temperature changing patterns of webs, bottom plates and diaphragm platesof the concrete box grider under action of hydration heat.(2) Respectively established 0# beam segment of the finite element solid model withMIDAS/Civil. According to the layered casting construction stage of concrete pouringsituation, analyzed the hydration heat of the two beam segments. Through compared thecalculation results and the measured data, found that the internal-external maximumtemperature difference from 1.0m to 2.5m thick concrete structures will lag 4~10 hoursbecause of the different thickness of the concrete structures. In the same conditions, thetemperature field of hydration heat is determined by thickness of concrete.(3) Do finite element analysis with MIDAS/Civil to heat insulation measures and pipecooling measures which are used to control the hydration heat, compared to the constructionpractice calculation results, the results showed that the two measures can make the internaland external temperature effectively controlled, but the pipe cooling measure is better.(4) Comparative analyzed the measured date and calculated result, verified the accuracyand feasibility by using the finite element software simulation of concrete temperature field ofthe hydration heat, then summarized the temperature control measures of concrete box grider. (5) Combined the cracks problems in process of construction of main bridge ofDongguan Channel bridges, in-depth analyzed the early concrete temperature crack formationmechanism and causes, then some suggestions are proposed and crack control measures sregiven, to guide the construction of similar bridge have certain application value.