## 1 Introduction  
In recent times, the health monitoring of concrete dams has become a topic of great importance and involves monitoring the static and dynamic behavior of large dams [1]. One of the most important parameters that strongly influence the static behavior of concrete dams, especially arch dams, is temperature. For this reason, it is very important to know the seasonal temperature distributions in concrete dams, as they affect the thermal loads, which can cause high stresses in concrete dam structures and significantly affect the occurrence and behavior of cracks, as well as displacements. The effects of climate change and global warming, which may result in a general temperature increase in these structures, need to be considered [2]. Early fundamental research in the field of thermal analysis related to nonlinear and nonstationary heat conduction through a solid, considering suitable boundary conditions, was carried out by [PERSON] et al. [3] and [PERSON] [4], whereas some years later [PERSON] et al. [5, 6] presented a methodology based on the finite element method (FEM), which could be used to determine seasonal temperature and stress distributions in concrete gravity dams. Using this methodology, the thermal behavior of concrete dam structures (from arch to gravity) has been much better analyzed, both in the phase of dam design [7,8] as well as in the later phase of monitoring and surveillance of the dam [9,10]. It has been discussed in an increasing number of articles dealing with: stress analysis of concrete structures, which are affected by variable thermal loads [11]; the determination of the periodic temperature field in a concrete dam [12]; the numerical calculation of temperature in a mass concrete [13]; thermal and stress analysis of the discussed roller-compacted concrete dam [14]; and the effect of environmental impacts on thermal stress analysis of the discussed arch concrete dam [15]. Some other authors have discussed the development of new numerical models, such as the model for the analysis of concrete dams due to environmental thermal effects [16], hydrostatic and temperature time-displacement model for concrete dams [17] and hydrostatic seasonal state model for monitoring data analysis of concrete dams [18]. Some others have reported about the sensitivity study of thermal fields in massive structures [19], and about the thermal protection of concrete dams in northern regions [20]. In recent years a large amount of research has been performed in connection with the thermal performance of concrete dams, in which the effects of the changing surrounding conditions were taken into account. Some researchers have focused on detailed studies of displacements dealing with: analysis of concrete dams based on seasonal hydrostatic loading [21]; seasonal thermal displacements of gravity dams, which are located in cold regions [22]; the method of dam deformation due to thermal actions [23]; and correlation between the air temperature and the daily variation of structural response [24]. Other researchers have discussed cracks in the dam structures [25,26], whereas others have analyzed temperature-induced stresses in concrete dams [27,28]. Others again have studied shading effects [29,30] and the effects of solar radiation [31,32], and some reports have discussed temperature fields in the case of super-high arch dams [33,34,35,36]. Some other researchers have recently compared the field monitoring data with the results of numerical analyses of temperature distributions also for other structures ([PERSON] et al. [37] for long-span suspension bridges, [PERSON] et al. [38] for superall structures) and for specific materials ([PERSON] et al. [39] for concrete-encased steel girders). A literature review of the research on the dam monitoring data analysis methods, which are very important for monitoring the dam safety and where the influence of the environmental variables (e.g., water level, temperature) has been involved, has recently been presented by [PERSON] et al. [40].