## 2 Thermal Stress Control and Prevention of Crack Formation  
The condition for crack formation in concrete is that the maximum tensile stress surpasses the concrete tensile resistance:  
\[\sigma_{1}(\tau)>f_{z}(\tau), \tag{1}\]  
where \(\sigma_{1}(\tau)\) represents maximum tensile stress and \(f_{z}(\tau)\) represents the tensile resistance of concrete at a given moment and location in a structure.  
The process of crack formation in a concrete gravity dam (CGD) can be avoided by construction measures, such as building in separate monoliths and casting concrete blocks in phases, while it is necessary to use slow-hardening cement in smaller quantities in the process of preparing the concrete mixture, as well as lowering the temperature by using ice, cold water or cooled aggregate, together with an adequate curing method after pouring the concrete [37, 38].  
Construction of CGD in separate, mutually independent monoliths [39] implies forming the contraction joints (Figure 1A) between the neighboring monoliths, which enables the relaxation of thermal tensile stresses (TTS), thus preventing or mitigating the crack-forming process. The water resistance of a dam is provided by connecting the monoliths with waterstops made of an elastic water-resistant material (Figure 1A). With properly arranged contraction joints, cracks that could be a consequence of differential settlement induced by topographic and/or geomechanics conditions can be avoided. Experience has shown that the distance between the two adjacent contraction joints, which is defined as the monolith length, is usually between 6.0 and 16.0 m, and it is conditioned by the requirement that cracks in concrete do not exceed the acceptable limits [40].  
Unlike the contraction joints, the construction joints (Figure 1B,C) are temporary and shall ensure proper adhesion between blocks to obtain a monolith unit. The construction joints, which can be vertical, horizontal, and staggered, serve the purpose of reducing the initial stresses and the possibility of early cracking, which is a consequence of shrinkage, by enabling a more rapid and even emission of heat to the outside environment which  
Figure 1: Waterstops, blocks, and joints of a concrete gravity dam: (**A**) waterstops between adjacent monoliths; (**B**) combination of long blocks and staggered joints; (**C**) combination of long blocks and vertical joints.  
surrounds the concrete. The construction joints must be previously prepared to secure a proper connection between the old and the newly cast concrete block [40].  
Phased pouring implies casting concrete blocks according to the schedule of construction, which must be the result of a previously conducted thermal stress analysis (TSA) with the aim of reducing TTS. There are several ways to distribute blocks inside a monolith (Figure 1B,C): long blocks, staggered joints, vertical joints, and a combination of long blocks and vertical and/or staggered joints. The length of a block (in the direction toward the riverbank) is a dimension that is usually equal to the monolith length; the width of a block (in the upstream-downstream direction) depends on the monolith width and is typically up to 25 m, while the height of a block is usually from 0.5 to 3 m. The concrete block remains free to cool down for at least three days [40].  
Based on the aforementioned, a conclusion can be made that, in the design process of CGD, special attention should be given to the definition of the structural elements, construction dynamic plan, as well as the choice of the concrete mix, which implies excellent knowledge of all the parameters and factors which influence the process of stress field (SF) development, leading to formation and propagation of cracks. Contemporary methods of thermal stress analysis, which are based on the application of the finite element method (FEM), offer the possibility of incorporating a large number of parameters and factors of importance for the process of computational modeling of this phenomenon.