Influence Of Uncertain Factors On The Thermal Stress Of Concrete Dam

Thermal stress is one of the main factors of dam cracks, when the stress exceeds the capacity of concrete cracking, the cracks will appear. In the practical construction, the temperature of concrete will become stable by the highest temperature of cooling to the runtime, often causing considerable tensile stress in the interior, sometimes the thermal stress may exceed the stress caused by other loads. In the past concrete construction, we tend to obtain specific thermal stress because specific parameters are given. But in the actual construction process, factors are varied and uncertain, this paper investigate the influence of uncertain factors on thermal stress through the interval theory.In this paper, by using finite element method, interval theory and choosing linear expansion coefficient, elastic modulus, temperature increment and creep rate as 4 main parameters, the calculation formula for the interval of thermal stress with variation of parameters is deduced. That establishes the calculation method for the uncertainty of thermal stress of concrete structure under the influence of factors. On the basis of the main factors of concrete, finite element method is used to study the sensitivity of the influence on thermal stress from different factors including the linear expansion coefficient, elastic modulus, adiabatic temperature rise and creep rate. At the same time, in the common influence of pouring concrete thickness and intermittent period, the change rule of the thermal stress is explored. Finally obtained the sensitivity of the influence on thermal stress from linear expansion coefficient, elastic modulus, adiabatic temperature rise and creep rate, and also got a relation between the maximum thermal stress and intermittent period t.The calculation results show that the linear expansion coefficient, elastic modulus, adiabatic temperature rise and creep rate are the 4 main factors affecting the thermal stress. The maximum of the thermal stress has a linear relationship with the linear expansion coefficient, elastic modulus, adiabatic temperature rise, and creep rate in case of other parameters unchanged. Among these factors, the elastic modulus on the thermal stress is the most sensitive, the adiabatic temperature rise and the linear expansion coefficient are next, creep rate on thermal stress is the least sensitive.The rules of effect of construction process on the thermal stress are as follows: the smaller of pouring layer thickness, the maximum of the thermal stress is smaller; with the increase of the intermittent period, the maximum of the thermal stress increases to the highest, and then decreases.