Abstract
In this study, a numerical analysis model to predict the thermal cracking of massive concrete structures is presented. In this model, the mean temperature rise Tm and the internal temperature difference △T are caluculated by Schmidt method. Thermal stress of concrete member is considered as summation of external restrain stress corresponding to Tm and internal restrain stress corresponding to △T. The parabolic internal temperature distribution is applied. Thermal stresses at the surface of concrete member and at the center of concrete member are calucurated by H. Rusch's step-by-step creep analysis method using the middle stress, which considers strictly delayed elastic deformation. The value of the risk of cracking; Vr, c is defined as the ratio between the thermal stress in concrete member at considered age and the tensile strength of concrete at that age. And judgement of cracking is done by maximum value of Vr, c. Following results are obtained from the application of this model to analysis of factors which are considered to influence to thermal cracking of massive concrete structures. 1) The risk of cracking is different in parts of member. If degree of restrainment is small, cracking appears at the surface of member during member temperature asending branch and if degree of restrainment is large, it appears at the center of member during member temperature desending branch. 2) Most important influence factor for the cracking of massive concrete member is degree of restrainment. Other material and construction factors, such as cement type, concrete placing temperature, and cement content do not so much influence to the risk of cracking as degree of restrainment.
