Thermal-mechanical Analysis And Crack Research Of Mass Concrete Bearing Platform

Mass concrete constructures have been widely applied in water conservancy project, along with the improvement of span of bridge structures on our country, more and more mass concrete structures have appeared in the construction of bridge engineering. There is some different between bridge engineering and water conservancy project, mass concrete structures appear more as zero block of rigid frame bridge and pylon of cable-stayed bridge. During the use process of mass concrete constructures, the problem of easily cracking during the process of the hydration is to overcome, due to its large size, in the process of hydration heat there will be a larger temperature difference between insite and outside, if improperly controlled it is easy to crack.Cracks will cause a series of secondary diseases, such as the late steel bar corrosion, concrete corrosion and reduced durability, life and so on.This paper, taking a 120 meters mainspan continuous rigid frame bridge in the western area as the engineering background, on the basis of site test data, and combined with the numerical model, and finally analyze the temperature effect rule of mass concrete pile caps. And based on the above, a parameter analysis is carried out for the various factors affecting the mass concrete temperature field.In this paper, main work is as follows:1) The paper lists the scholars at home and abroad in the field of the concrete hydration heat research, introduces the principle of concrete temperature effect calculation; Analysis of influence factors of concrete creep,and common creep prediction model is given.2) Investigation of bridge site environment is carried out, including site geological and hydrological data, the meteorological environment parameters, which provides the basis for numerical analysis.Carry out the site test of pile caps hydration heat temperature, combining with the results of numerical analysis, analyse the distribution between the site test date and numerical analysis, and verify the reliability of the numerical model.3) Carrying out site test and draw the curve of temperature change, through collectting outlet temperature and smoothing the data, the paper derive the calculation method of reasonable dismantle time for the pile caps. The result of the calculation is applicable for the subsequent pile cap which have the same design parameters.4) Based on the numerical model, the paper carry out a parameter analysis for zhe pipe cooling, through changing the parameter such as water flow, water temperature, pipe diameter, discusses its influence on the effect of concrete temperature; Analysis of the influences of concrete pouring temperature and external heat preservation measures to the stress distributions is conducted, providing a reference for the temperature control measures.5) In view of the cold wave and the temperature difference between day and night that often appeared in the bridge area, the paper carry out relevant parameter analysis, and sum up the relationship between cold wave intensity and the convection coefficient and stress of concrete surface. Putting forward the critical code strenth and the critical equivalent convective coefficient that can offset cold wave impact, the paper provides reference for the site heat preservation.