2. LVL STRUCTURES IN FLOORS, WALLS, ROOFS AND IN SPECIAL APPLICATIONS Lapwall, Metsä Wood Stressed skin rib panels and box panels For long-span roof elements, the composite action of glued stressed-skin panels can be utilized between LVL-P ribs and LVL-C panels. Rib panels can be used, e.g., for non-heated shelters, and insulated box elements for hall constructions. Depending on the snow loads and height of the elements, span lengths can be 10-20 metres. The structure is simpler than elements with purlins as no secondary beams or battens are needed. However, if the rib spacing is large, up to 1250 mm, the top panel must be thicker because the main direction of the LVL-C is along the ribs, and the panels need to transfer the snow load to the ribs in the secondary direction. Figure 2.41. LVL box panel element. The ceiling panel thickness depends on the fire resistance requirements. Depending on the reaction to fire requirements of the project, LVL-C bottom flange panels can be left visible or covered with gypsum board. A great advantage of box elements is that suspension installations, such as ventilation channels, can be freely fixed with screws anywhere on the ceiling surface because the LVL-C panels provide a solid base for axially loaded connections. An LVL box element roof can be realized as a cold roof or warm roof solution, but the building physics design needs to be done separately based on the project-specific indoor and outdoor conditions. Stressed-skin panels can be CE marked based on the ETA assessments of the element suppliers 22, 23. LVL Handbook Europe 75
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