It is well known that cracks of the massive concrete structure are caused by various factors. The property of the concrete that is employed to the crack analysis include scatter. In order to evaluate the analytical values, it is necessary to grasp information on the influence of scatter in material properties. An analytical procedure for the mass concrete structures which have uncertain properties in the materials and environment is herein proposed. The variances of thermal stresses in the structure having uncertain material properties are herein evaluated from the values of sensitivity obtained from the sensitivity analysis and the approximate theory using Taylor's expansion. The crack probability is evaluated from the scatter that was obtained from the analysis. Furthermore, in order to improve the accuracy of the estimation of thermal cracking, an analysis where thermal stresses are considered to be dependent on the temperature of heat of hydration process and strength development is carried out.
　Chapter 1, Introduction, describes briefly the background of this study, and the thermal cracking of mass concrete. This chapter also summarizes the current state of studies on the estimation of thermal cracking and the analytical method of uncertainty systems. The purpose and organization of this thesis are concretely given in this chapter.
　In chapter 2, the sensitivity analysis method is applied to transient heat conduction analysis by the finite element analysis. An analytical procedure which deals influencing factors affecting to temperatures in the structure is proposed. Factor analyses are conducted for the thermal characteristics affecting to thermal analytical results by means of the method of sensitivity analysis. Variances of the temperatures in the structure having variable thermal characteristics of concrete and environment were evaluated from the sensitivity obtained by the sensitivity analysis and the approximated theory using Taylor's expansion. As a result, the adiabatic heat generation characteristic exerts an influence to a nodal temperature largely. Also, results obtained with this analysis agree well with the results of a Monte Carlo simulation within the range of a 30% coefficient of variation. An appropriately of this analysis was confirmed.
　In chapter 3, sensitivity analysis method was applied to stress analysis by the finite element analysis and the CP. method (CL method). Variances of thermal stresses in the structure having uncertain material properties were evaluated from the values of sensitivity obtained from the sensitivity analysis and the approximate theory using Taylor's expansion. A slab structure, a wall structure and a rectangular slab are analyzed as numerical examples. As a result, in the case that each material property varies 10%, the stress that occurred varies 20%. The analytical result did not depend on the stress analyses (CP. method, CL method and EM). A young's modulus and a coefficient of thermal expansion of concrete exert an influence to calculated result of stresses.
　In chapter 4, the crack probability is determined from S-R (Stress-Resistance) model including scatter of stresses that occurs in the concrete obtained from the analysis discussed in chapter 3 and the scatter of tensile strength of concrete. Furthermore, these relationship between the thermal crack index and the crack probability were evaluated. As a result of an analysis, the relationship between thermal crack index and crack probability designated in the concrete standard specifications is close to the case that each property varies with 15%. Scatter of 15% is a proper value compared with a scatter of a compressive strength in a site. Also, the relationship between thermal crack index and crack probability can be applied to both the slab structure and wall structure.
　In chapter 5, in order to obtain more accurate estimation of cracking, the analysis includes the properties dependent on the temperature. The conventional thermal analysis of concrete structures has been carried out with the assumption that the same hydration as the adiabatic condition advances on the same rate of the adiabatic temperature rise test. Also, the strength of concrete is considered to be the same at any location. However, in fact the rate of hydration changes due to the temperature at the location. The velocity of heat of hydration and the strength development are influenced to the temperature at the location. In other words, a hydration is promoted more, as the temperature of a system become higher. As a result, the velocity of hydration becomes faster. Nonlinear thermal analysis dependent on the temperature was considered was carried out in 5 chapter. Furthermore, stress analysis is carried out for structures with strength development dependent on the temperature by using the block CP. method proposed in this study.
　In Chapter 6, Conclusions, summarizes of this study and the problems remaining for further study are described based on the present results.

▲ Master's thesis ▼