http://www.revmaterialeplastice.ro MATERIALE PLASTICE ♦55♦No. 2 ♦2018 219 Reaction of a Sandwich Type Structure to Static Stress Under the Action of the Snow NICUSOR BAROIU, ELENA FELICIA BEZNEA*, IONEL CHIRICA, IONEL IACOB Dunarea de Jos University of Galati, 47 Domneasca Str., 800008, Galati, Romania Structural elements of special industrial constructions can be often subjected to time variable stresses. One of the main stress is the snow action, which is considered to be one of the most severe tests. In the study, the static snow action on a tank cover from a pickling plant on the ArcelorMittal Galaþi platform is analysed. The material structure of the cover is sandwich type with skins made of steel /layered composite and core made of polystyrene foam. The purpose is to determine, by FEM analysis, the deformation mode and the stress condition of the cover under the action of load, for two models of sandwich type structures, steel-polystyrene- steel, respectively composite-polystyrene-composite, with different faces thicknesses and cores. Panels are applied simulative a load of snow of different thickness, the distribution of snow on the surface of the panels being considered uniform in order to determine an optimum combination of faces and core thickness as well weight and economic cost too. Numerical analysis models with finite elements of SHELL 3L sandwich type structures are used. Keywords: finite element method, sandwich panel, buckling, static action In the pickling tanks, the oxidized surface created during the hot rolling of steel is removed, with the help of acids (hydrochloric, sulphuric, hydrofluoric, etc.), at high temperatures. Some steels have higher pickling times compared to normal, with low carbon steel content, a fact that makes these special industrial tank type constructions of particular importance [1]. Their protection and especially of those of very high volume, must correspond to all areas of use: fire resistance, resistance to attack of chemical and environmental agents - temperature variations, solar radiation, snow action, etc. [2, 3]. In the study, it is described the way of replacing the metallic cover, degraded, of an existing pickling equipment found on the ArcelorMittal Galati platform, with a similar dimensional structure, analysed from the point of its loading with different amount of snow. This structure is associated with a roof in two slopes where snow load is considered, in this case, to be a fixed and static action expressed as load per square meter of horizontal projection of the support and only in cases of exceptional snow agglomeration, the load can be considered accidental and variable [4-6]. To determine the own weight of this element of construction, has been considered the dimensions of the element as well as the material of which it is made, represented in the calculations by the apparent specific weight [7]. In order to determine the load capacity, the finite element analysis method is often used, most often for the purpose of determining deformations and equivalent stress, depending on the nature of the material of the faces, the core and the thickness of the layers, correlated with their dimensional values, but also depending on the way to apply the tasks [8-10, 14]. The study proposes the analysis of two sandwich type structures, made up of metallic materials faces, respectively, of polyester resin composite material and bidirectional fiber glass fabric. From the weights calculation, it was decided to realize a sandwich type structure with two 2 mm thickness, core of extruded polystyrene with 20 mm thickness, and respectively 50 mm. Given the structural simplicity, the weight-strength * email: elena.beznea@ugal.ro; Phone: 0743605440 ratio, the exceptional anticorrosive properties, such a structure, widely used in most industrial fields, can be considered optimal in terms of elasticity, thickness, weight and cost properties [11-13]. Therefore, for ease of physical realization of the structure, it initially started from modelling performed in the graphical environment Autodesk Inventor (fig. 1). Fig. 1. Sandwich type structure modeled in Autodesk Inventor graphical environment Since the initial reservoir cover type structure is relatively large (3m x 2.5m x 0.22m), it requires a hydraulic lifting system in a position that allows it to be opened up to 90°, with the possibility of locking the cover in the open position by the help of safety devices (fig. 2). The opening is made in the vertical plane with the help of a hydraulic system, comprising the operating cylinders and the hydraulic pump, the closing being accomplished by releasing the hydraulic oil from the cylinder. Finite element modeling of the sandwich type structure In the study, the cover is statically analysed when the load given by snow, of 2.5 kN/m 2 [4], in the form of surface pressure, has the following values: p 1 = 7.66 . 10 3 N/m 2 ; p 2 = 9.58 . 10 3 N/m 2 ; p 3 = 11.5 . 10 3 N/m 2 . The numerical analysis was performed on sandwich type structural composite plates, simply supported on two sides at 3000 mm x 0.07 mm. The loading was carried out with a uniformly distributed pressure on each rectangular surface of 3000 mm x 1277 mm. To determine the displacements and stresses of sandwich composite plates,