Abstract. The sandwich beam can be considered as the multi-layered structure with a symmetrical cross-section. In this paper is assumed that the structure is created by periodical repetition of a unit cell. The influence of its size on the beam's static behavior in bending was analyzed. The variation of the unit cells number affects the size of the cell, so the static analysis was performed -the flexural stiffness and the beam's deflection were determined as functions of the unit cells number. The two configurations of the sandwich beams were considered: the beam with the constant cross-section along its length and the beam with the periodically variable cross-section. The graphs of the beam's flexural stiffness and deflection variations in terms of the unit cells number were obtained. It was concluded that after a certain number of the cells, the core's density does not further influence the behavior of the sandwich beam, under the given loading conditions. The conclusion from comparison of the two configurations is that the sandwich beam with the variable cross-section behaves somewhat better than the beam with the constant cross-section. The FEM analysis has verified all the conclusions from the analytical solution about the sandwich beams behavior when subjected to bending.

The influence of geometric parameters on behavior and stiffness of sandwich plates with corrugated core is considered in this paper. The following parameters were analyzed: ratio of core sheet and facing sheet thickness and the ratio of the core's pitch to the core's depth, as well as the corrugation angle. It is shown that changes of these parameters can contribute to increase or decrease of the corrugated sandwich plate stiffness.

The research presented in this paper indicates one of the options for improving the management of environmental resources by increasing the occupancy rate of capacities in the spas of the Republic of Serbia (RS). It is motivated by the current needs of the tourism industry for ideas that can increase the level of potential utilization of spas in the Republic of Serbia. The aim of the paper is to use research to test a basic hypothesis, that attracting families with small children can increase the occupancy rate of the spas' capacity in the Republic of Serbia. The paper presents table research and field research. Table research was based on official data from the documents of the Republic of Serbia. The field research, presented in the paper, has been carried out on a sample of 122 respondents (parents with small children), that respond in the questionnaire with 20 research questions about the survey topic. The research results confirm that the creation of better conditions for the stay and pleasure of families with small children in the Serbian spas, and their encouragement and motivation, may greatly influence the increase of occupancy rate of the spas' capacity in the Republic of Serbia. This result showed to the authorities and management bodies of the tourism industry and spas in the Republic of Serbia that there is sense to take actions for a massive motivation of families with young children to use the spa throughout the year. The truthfulness of main hypothesis H(0) is confirmed. Furthermore, it has also been shown that, by the creative approach, it is possible to generate and check other ideas for increasing the occupancy rate of spas' capacity.