Issue 39

J. Flodr et alii, Frattura ed Integrità Strutturale, 39 (2017) 62-71; DOI: 10.3221/IGF-ESIS.39.08 63 are disadvantages. Users have to know background of these methods as well as their possibilities and more detailed input data (e.g. material models, real working diagrams). S TEEL SUSPENDED CEILING hile solving construction of steel suspended ceiling a special approach was required. Therefore this research was created to deal with construction for clean areas for example pharmaceutical and chemical laboratories, paint shops in industrial areas etc. Special approach was required for service and technological loads. Ceiling has to be walkable to allow service load and to have maintainable conduits such as ventilation and electrical wiring. Other requirements were heat and sound insulations. EC standards cannot be used in case of these requirements [10]. Therefore 3D model and stress-strain evaluation were used for design. Numerical analysis takes physical and geometrical nonlinearities into account and is in accordance with EC [11, 12] and [13]. Physical experiment was made to check design of real structures and deflections and to validate calculation process. Suspended panel ceiling consists of connected sandwich panels which are hung on construction by rods. This is a development of method presented in [3], but working diagrams are not used there. Considered loads acting on a cassette are: Surface load 1.00 kN/m 2 and point loads 4x1.00 kN (max. area 10 m 2 ). Internal suction is not considered in this case. However extreme value of internal pressure (300 Pa) is considered in short term. Dimensions of panel are 1200x2300x82mm. Sandwich panel consists of three main components as shown in the Fig. 1 on left. Bearing part is made from steel plate cassettes (thickness 0.80 mm), two symmetrical thin walled C profiles which are placed between the cassettes and the last component is non-bearing and it is made from mineral wool insulation. Figure 1 : Detail of panel of suspended ceiling (left) suspended ceiling with surface load and 6x point load (right). Minimal yield strength of steel is considered 235MPa. Panels are supported by L profiles which are connected by steel buckles and Z clips. These clips are suspended on main construction by rods Ø10 mm S235. L profiles are from steel S235 as well. Sandwich panels are fixed to L profiles by screws. Part of construction is manufactured to check the functionality of design. Model consists of 4 panels and 6 rods suspended on main steel structure. Total dimensions are approximately 2350x4800mm. Overview of model is in the Fig. 1 (on the right). Working diagrams of steel were made from samples made from materials used in model. Figure 2 : Steel samples. W