2. LVL STRUCTURES IN FLOORS, WALLS, ROOFS AND IN SPECIAL APPLICATIONS In roof structures that have higher resistance to fire requirements than the nail plate trusses can achieve, an LVL-P bottom chord can be designed to carry the loads in the case of fire as a beam, allowing the rest of the frame to be designed to normal temperature requirements. Sides are protected with stone wool insulation and the top edge is supported against lateral torsional buckling. When roof trusses are left visible, LVL-P king post or queen post trusses with dowel type connections are an aesthetically pleasing solution. They are the most competitive option for 15-22 metre spans in cases where double-tapered solid beams are uneconomical due to the roof slope and where the fire resistance requirement is R15. With larger trusses, e.g. for sports halls, LVL can be used for all truss components, as diagonals combined with glulam chords, or in hybrid structures with steel members. A 3-pin frame structure is a good solution when the interior height of a hall needs to be maximized. The built-up column part of the frame has two LVL-C panels which are screwed and glued together with wooden battens to form a box structure. The intermediate battens are shorter than the LVL-C panels which creates a space for the rafter part of the 3-pin frame to sit in. The battens should therefore have the same width as the rafter. The rafter part of the 3-pin frame is a single LVL-P beam, box beam or a glulam beam. The moment-rigid corner is a timber-to-timber connection made with bolt, screw or dowel circle without separate steel parts. The size and number of fasteners in the corner connection depend on the size of the hall and the loads. The crosswise veneers in LVL-C panels provide good connection strength and prevent the risk of corner cracking 24. To optimize material use, it is recommended to choose column panel and rafter sizes that fit the LVL panel width when they are diagonally cut as a single taper. The wider end is at the moment-rigid corner connection and the narrower end toFigure 2.80. Left: LVL queen post trusses, Fupicsa production hall, Spain. Right: King post trusses, Manese Wassström, Tammisaari, Finland. Metsä Wood Metsä Wood Stora Enso Figure 2.81. LVL roof trusses. Ydalir, France. wards the pin points: the ridge and foundations. 3-pin frames are the most competitive when the capacity of a single LVL-P rafter is adequate for the loads. In areas with high wind loads a small roof angle is preferable and in areas with high snow load a larger roof angle is preferable. The economical span range is 10-30 m 19. Figure 2.82. Principle of diagonal sawing of LVL panels to produce single-tapered column and rafter members for 3-pin frames. The dimensions should be chosen so that the full panel width can be used. LVL Handbook Europe 99
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