Analysis of the behavior of the floating systems used for boundary of river-sea recreational activities area
Authors: Gabriela Ene Alexandra , Mihai Carmen , Jomir Mihaela , Jomir Constantin 
Published: June 2023

The network of river courses that cross the territory of Romania has a total length of 118,000 km, to which is added the aquatic part of the Romanian coast (the Black Sea and the harbors), with an area of 39,940 km2. From this territory the UNESCO Biosphere Reserve (the shore of the Delta Danube and the Razim Sinoe complex) cover an area of over 6000 ha. Under these conditions, tourism that includes recreational activities (if the environment allows it) can be extended within the arranged natural aquatic reserves, mainly including the swimming. The natural areas for swimming are protected areas to avoid possible risks of pollution and are specially arranged, respectively: for depths up to 1.50 m, the slope is uniform and the inclination respects the ratio of 1:10 - 1:15, while, for greater depths, the inclination of the slope does not exceed the ratio of 1:3. Considering the strict restrictions imposed on the recreation area, the swimming areas must be strictly and visibly delimited from the areas where other recreational activities are carried out (mooring of charter ships, practicing water sports, etc.) with possible health risks. Additionally, special attention is paid to the delimitation of the bathing area with a depth of less than 0.70 m, for children and people who do not swim for various reasons. In these particular situations, to avoid possible accidents, the delimitation and marking is performed with the help of floating systems made of composite material based on woven structure matrix. For the purpose of ensure the delimitation and signalling of the maritime and fluvial areas, for a depth of 3 m, the researches were focused on the digital development of a flexible composite structure. The geometric, dimensional and structural elements of the composite architecture were predicted based on FEM modeling and were calculated for a solid body in the form of a right circular cylinder. The design and developed flexible structure was experimented at the shore and the main conclusions leaded to the following: i) the composite material behaved appropriately, and, during the monitoring period of 72 hours, no potentially interventions caused by damages were needed; ii) no damage of the textile material or change in geometrical of the solid shape was recorded. The experiments carried out in open sea conditions required the consideration of the specific features of a continuously moving surface (due to sea waves and currents), with large temperature variations and difficult weather conditions. During the experimental trials, the floating systems were placed at Lat. 43.985 Lon. 28.607 Altitude 50m and the meteorological observation were made at every 24 hours within a period of 10 days, during May when dangerous phenomena, such as descending gusts (white squalls, formed as a result of the rise of water in the atmosphere with the cumulonimbus clouds development) and nebulousness were recorded. Regular inspections were performed and the appropriate behavior of the composite material used as core part of the floating marking/signalling systems was registered.