Anlysis And Research On Hydration Heat Of Mass Concrete In Long-span Bridge With High-piers

With the development of high-speed railway construction in the mountain,long-span bridges with high-piers have been widely used in the construction ofhigh-speed railway. In order to meet the requirements of bearing capacity, stiffness andstability, the members of bridge tend to have a large size. The hydration of the cementcan make concrete cause a rapid temperature rise. Due to the poor thermal conductivityof the concrete, the heat built-up in the internal isn’t distributed easily. Due to thepresence of temperature difference between inside and outside of the concrete body, thetensile stresses exist on the surface. When the tensile stresses exceed the allowabletensile strength of the concrete, it will produce temperature cracks, thus affecting thenormal use of structure. With the extensive application of mass concrete in long-spanbridges with high piers, the bridge engineers have paid more attention to the hydrationheat of concrete.With the background of Xinfuyuan Reservoir Bridge, this paper relies on the theMinistry of Railways research project "Technology Research on Design of High PierStructure of High-speed Railway Bridges in Mountain". This paper selects15#pier capand12#pier segment (22.898m~27.398m) for the study and analyzes the thermal fieldand stress. The main research work and conclusions are as follows:①According to the structural characteristics, it made a corresponding program tomonitor the hydration heat temperature. In the program it chose the suitable location toarrange measuring points. Through the analysis of the measured temperature data, itshowed that the concrete hydration heat temperature distribution along the pier wallthickness was symmetrical parabolic form. With the quadratic polynomial and cubicpolynomial fitting methods, it got the principle of temperature distribution along thethickness.②According to the actual conditions, it defined the thermal performanceparameters of concrete and boundary conditions. With MIDAS/Civil2010, a finiteelement model was established for numerical simulation. Comparing the calculatedtemperature value and the measured data, it showed they were more consistent. Toverify the accuracy of numerical simulation, and laid the foundation for the numericalexperiments.③Through the analysis of the factors of the heat of hydration in mass concrete, this paper proposed some temperature controlling measures. With the analysis of therelationship of the different varieties, the amount of cement and the core temperature ofconcrete body, further optimizing the mixture ratio can reduce the concrete temperature.Focusing on the arrangement form, spacing, diameter, material, flow rate, watertemperature and water time of the cooling pipe, this paper proposed the optimization ofthe cooling water pipe layout scheme and layout recommendations. By analyzing theimpact of the insulation material, it determined the most effective insulation measuresfor mass concrete. Analyzing creep of concrete characteristics of the influence oftemperature stress, the concrete creep thermal stresses can be calculated by stressrelaxation coefficient.