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Table 3 Results of the optimisation (values of best design are underlined) Tablica 3 Rezultati optimizacije (vrijednosti najboljeg dizajna su podvucene)

Table 3 Results of the optimisation (values of best design are underlined) Tablica 3 Rezultati optimizacije (vrijednosti najboljeg dizajna su podvucene)

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4.3 Joints When the response of the panel is known, the structure can be checked against strength and maximum displacement criteria. The strength criteria include: overall buckling of the panel, local buckling of panel’s structural members, faces and web plates, and their maximum tolerable local loads. Local buckling of the panel’s structural members can be calculated with good accuracy, with the formulae presented for example in the classification society’s rules or handbooks of strength of materials. Figure 3a shows an example of the failure process of corrugated core steel sandwich panels under constant pressure with simply supported edges. The panel dimensions were: length 2500 mm, breadth 340 mm, height 53 mm, face plates 1 mm, web plate 0.7 mm. Yield strength for the face plates was 153 MPa and for the webs 184 MPa [16]. Figure 3b illustrates the middle part of the panel after testing. Local impact needs to be studied as well due to the typically thin top face plates. The behaviour of steel sandwich panels under local impact loading was investigated by means of laboratory testing, FE simulations and analytical modelling [25]. The FE simulations enabled the following of the impact process and attainment of the information about the behaviour of a panel throughout the impact. Based on this and the observation during the laboratory experiments, an analytical model has been developed analysing the deformation energy. The deformation energy, in case of the panel with filling, can be partitioned into three main components: bending and membrane energy of the top plate and energy absorbed by the filling material. Deformation depth and the shape can be then evaluated by equalising the kinetic energy of the striking body with the deformation energy of the panel as shown by Tabri in [25]. 4.2 Strength criteria Mindlin shell elements to be used for 2D Finite Element Analyses. Stiffness properties were derived analytically for both empty and filled panels with I-, C-, O-, V-, Vf- and Z-core geometries. plate collapse and top plate denting, the derived formulations for foam filled steel sandwich panels under static loading are presented by Romanoff in [24].
4.3 Joints When the response of the panel is known, the structure can be checked against strength and maximum displacement criteria. The strength criteria include: overall buckling of the panel, local buckling of panel’s structural members, faces and web plates, and their maximum tolerable local loads. Local buckling of the panel’s structural members can be calculated with good accuracy, with the formulae presented for example in the classification society’s rules or handbooks of strength of materials. Figure 3a shows an example of the failure process of corrugated core steel sandwich panels under constant pressure with simply supported edges. The panel dimensions were: length 2500 mm, breadth 340 mm, height 53 mm, face plates 1 mm, web plate 0.7 mm. Yield strength for the face plates was 153 MPa and for the webs 184 MPa [16]. Figure 3b illustrates the middle part of the panel after testing. Local impact needs to be studied as well due to the typically thin top face plates. The behaviour of steel sandwich panels under local impact loading was investigated by means of laboratory testing, FE simulations and analytical modelling [25]. The FE simulations enabled the following of the impact process and attainment of the information about the behaviour of a panel throughout the impact. Based on this and the observation during the laboratory experiments, an analytical model has been developed analysing the deformation energy. The deformation energy, in case of the panel with filling, can be partitioned into three main components: bending and membrane energy of the top plate and energy absorbed by the filling material. Deformation depth and the shape can be then evaluated by equalising the kinetic energy of the striking body with the deformation energy of the panel as shown by Tabri in [25]. 4.2 Strength criteria Mindlin shell elements to be used for 2D Finite Element Analyses. Stiffness properties were derived analytically for both empty and filled panels with I-, C-, O-, V-, Vf- and Z-core geometries. plate collapse and top plate denting, the derived formulations for foam filled steel sandwich panels under static loading are presented by Romanoff in [24].
The failure modes, which occur under high local loads, are web plate plastic collapse and denting of the face plate. Both might occur under static or dynamic (impact) loading. For web
The failure modes, which occur under high local loads, are web plate plastic collapse and denting of the face plate. Both might occur under static or dynamic (impact) loading. For web
Figure 5 The studied load case for the joints [26] Slika5 Prouéavani slucéaj opterecenja za spojeve [26
Figure 5 The studied load case for the joints [26] Slika5 Prouéavani slucéaj opterecenja za spojeve [26
other end of the panel, see Figure 5. The Radaj’s approach [26] was used to determine the stress concentration factors for typical joints as reported by Ehlers in [27]. A circle of 1 mm in diameter is modelled on the critical areas enabling thus more exact stress evaluation, see Figure 6.
other end of the panel, see Figure 5. The Radaj’s approach [26] was used to determine the stress concentration factors for typical joints as reported by Ehlers in [27]. A circle of 1 mm in diameter is modelled on the critical areas enabling thus more exact stress evaluation, see Figure 6.
Figure 7 illustrates example of the calculated stress concentra- tion factors. As seen, it is possible with certain joint designs to achieve values for the stress concentration factor varying between 2 to 3, which are fairly acceptable values. The upper values are for symmetric loading at the ends and the lower values for the asymmetric load, or the load acting only at the bottom plate. Although this indicates that joints with a high fatigue performance As can be seen from Figure 8, the conventional stiffened plating with 50 mm mineral wool fulfils the A60 requirement and Lascor sandwich panel with 50 mm mineral wool against fire is close to the A60 requirement. The insulation inside the Lascor is not as effective as the insulation outside the panel. The fire characteristics of the sandwich panel can be remarkably in- creased by using holes on the corrugated core plating (Figure 9), as this will decrease the thermal conductivity of the webs. For the sandwich panel the installation of mineral wool outside is also a lot easier than for the conventional deck structures with numerous stiffeners to be surrounded by mineral wool whereas for sandwiches, the coatings can be attached on a flat surface.
Figure 7 illustrates example of the calculated stress concentra- tion factors. As seen, it is possible with certain joint designs to achieve values for the stress concentration factor varying between 2 to 3, which are fairly acceptable values. The upper values are for symmetric loading at the ends and the lower values for the asymmetric load, or the load acting only at the bottom plate. Although this indicates that joints with a high fatigue performance As can be seen from Figure 8, the conventional stiffened plating with 50 mm mineral wool fulfils the A60 requirement and Lascor sandwich panel with 50 mm mineral wool against fire is close to the A60 requirement. The insulation inside the Lascor is not as effective as the insulation outside the panel. The fire characteristics of the sandwich panel can be remarkably in- creased by using holes on the corrugated core plating (Figure 9), as this will decrease the thermal conductivity of the webs. For the sandwich panel the installation of mineral wool outside is also a lot easier than for the conventional deck structures with numerous stiffeners to be surrounded by mineral wool whereas for sandwiches, the coatings can be attached on a flat surface.
Figure 9 The behaviour of steel sandwich under fire can be impro- ved by using holes on the core plates [28] Slika 9 PonaSanje Geliénog sendvié panela izlozenog vatri moze se poboljsati buSenjem rupa na plocama jezgre [28]
Figure 9 The behaviour of steel sandwich under fire can be impro- ved by using holes on the core plates [28] Slika 9 PonaSanje Geliénog sendvié panela izlozenog vatri moze se poboljsati buSenjem rupa na plocama jezgre [28]
In order to demonstrate benefits of steel sandwich panels we present one application in ship structures. A traditionally built hoistable cardeck, a representative increment/segment of which is seen in Figure 11, was redesigned with respect to minimum weight and cost, applying the I-Core panel for decking. A similar study was performed for the Vf-Core panel [29], however, this study did not consider optimisation of the supporting grillage structure. In Figure 12 we can see a diagram for the redesign process of a cardeck that results in several new optimised designs. After suggesting improvements, such as the application of sandwich panels, designer uses optimisation procedure to obtain the final optimised designs that can be compared and selects one design.
In order to demonstrate benefits of steel sandwich panels we present one application in ship structures. A traditionally built hoistable cardeck, a representative increment/segment of which is seen in Figure 11, was redesigned with respect to minimum weight and cost, applying the I-Core panel for decking. A similar study was performed for the Vf-Core panel [29], however, this study did not consider optimisation of the supporting grillage structure. In Figure 12 we can see a diagram for the redesign process of a cardeck that results in several new optimised designs. After suggesting improvements, such as the application of sandwich panels, designer uses optimisation procedure to obtain the final optimised designs that can be compared and selects one design.
Table 1 Main particulars of the ship Tablica 1 Osnovne izmjere broda The sandwich panel is considered to be filled with polyurethane to increase several properties, among them, the corrosion protection. Yet, the structural benefits, noted in [24] and in [25], were not taken into account. Nevertheless the costs were calculated and added to the total production expenses.
Table 1 Main particulars of the ship Tablica 1 Osnovne izmjere broda The sandwich panel is considered to be filled with polyurethane to increase several properties, among them, the corrosion protection. Yet, the structural benefits, noted in [24] and in [25], were not taken into account. Nevertheless the costs were calculated and added to the total production expenses.
Two alternative concepts are proposed for redesign: sandwich- grillage cardeck (Variant B), a sandwich panelled cardeck with grillage supporting structure seen in Figure 15; sandwich cardeck (Variant C), a sandwich panelled cardeck that only uses C girders on perimeter, seen in Figure 16.
Two alternative concepts are proposed for redesign: sandwich- grillage cardeck (Variant B), a sandwich panelled cardeck with grillage supporting structure seen in Figure 15; sandwich cardeck (Variant C), a sandwich panelled cardeck that only uses C girders on perimeter, seen in Figure 16.
5.5 Constraints Figure 18 Design variables of Variant B, for a) girder 1, b) girder 2, c) girder 3 and d) girders 4 and 5 Slika 18 Projektne variable inacice B , za a) nosaé 1, b) nosaé 2. c) nosaé 3 i d) nosaée 415
5.5 Constraints Figure 18 Design variables of Variant B, for a) girder 1, b) girder 2, c) girder 3 and d) girders 4 and 5 Slika 18 Projektne variable inacice B , za a) nosaé 1, b) nosaé 2. c) nosaé 3 i d) nosaée 415
Table 2. Parameters of optimisation Tablca 2 Parametri optimizacije
Table 2. Parameters of optimisation Tablca 2 Parametri optimizacije
Related topics:
Structural Fire SafetySteel StructurePRODUCTION ENGINEERINGSandwich construction
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