Research On The Creep Effect Of Box-girder Bridge Under Variable Temperature And Humidity Conditions

The temperature and humidity of the bridge structure in a service condition changes constantly. However, the code of bridge design seldom considers the creep effect of the bridge under the variable temperature and humidity conditions, ignoring it whether reasonable has yet to be fastidious. Therefore, this paper takes HengKeng bridge as the engineering background to study the creep effect of bridge under three different environment such as the temperature,the humidity and the temperature with humidity. The main research works from the following three aspects:(1) Due to the influence of the temperature and humidity on the concrete creep is the effect of the concrete age, this paper quoted the equivalent load age and the equivalent sustained load age to reflect the temperature and humidity effects on during the concrete curing period and using period. And collected the temperature and humidity data from 2002 to 2015 of ZhuHai calculate the monthly equivalent load age and the equivalent sustained load age under the influence of temperature, humidity, both temperature and humidity, the results show that humidity calculations of the age are different, and the temperature calculations of the age are similar, and the variation of the temperature and humidity are similar to the humidity in curing period. What's more, the average of creep coefficient calculated by ZhuHai monthly actual temperature and humidity are smaller than the same month of the calendar year. In addition, the modified result of monthly mean creep coefficient is consistent with the creep coefficient calculated by the actual temperature and humidity. When study concrete creep effect under the temperature and humidity conditions, could use the average of temperature and humidity instead of actual temperature and humidity creep coefficient calculation to reduce a large number of data collection work.(2)Due to the influence of the temperature and humidity during Cantilever-Construction there are differences in creep coefficient of different concrete segment. And this difference mainly caused by the construction schedule. Therefore, built the bridge model of Heng Keng by the finite element analysis software MIDAS/Civil to calculate creep deformation in different months. Compared creep deformation of construction with different months, the result show that the best time of construction is June, and the most unfavorable construction time is December, the temperature and humidity of June is relatively high, while the weather in December is relatively low, in order to reduce the bad effects of segmental creep coefficient difference of concrete structure, it is recommended the important structure that construction time optimization and selection of high temperature and humidity time for construction. In addition, compared with the creep deformation and the code values of three working conditions proved that only the humidity calculation values are close to code values, and the calculation values of temperature or both temperature and humidity are all bigger than code values. The main reason is that the code of bridge design only considers the effect of humidity on the creep effect of concrete and ignores the effects of variation temperature or temperature with humidity during normative calculation.(3)Because each plate of the box-girder in different temperature and humidity field, and the creep coefficients of each plate are different. In order to study the different creep coefficient of box-girder plate influence on deformation of the bridge, established MIDAS/Civil hierarchical bridge model of HengKeng, compared and analysis the creep deformation of hierarchical model and integral model under the influence of temperature, humidity and temperature with humidity. The calculation results show that integral model of creep deformation is bigger than the hierarchical model.What's more, the discrepancies caused by both temperature and humidity is ten percent, and the discrepancies caused only by temperature is eight point seven percent, and the discrepancies caused only by humidity is five percent. It was demonstrated that the creep coefficient difference of box girder has a certain influence on the creep deformation under the variable temperature and humidity conditions.