5. STRUCTURAL DESIGN OF CONNECTIONS Connection detailing Members should be pre-drilled when the diameter d of the screw exceeds 8 mm or the diameter of the smooth shank ds exceeds 6 mm. The diameter of pre-drilled holes for non-selfdrilling screws should be D = 0.5d - 0.7d, but not more than the inner diameter of the threaded part di. The thickness of the member should be at least: t=max{█(5d@(10d-30) ρ_k/400)┤ (5.38) where ρk is the characteristic density [kg/m3]; and d is the screw diameter [mm]. General spacings and end and edge distances are presented in Table 5.1. These values are valid for cross screw connections when the compressed and tensioned fasteners of the screw pairs are placed in separate longitudinal rows parallel to the grain, so that the spacing between the rows a2 is 4d and the staggered distance between the screw heads of a screw pair is not more than 3t1 parallel to the grain. Different types or sizes of screws must not be combined in the same connection. All screws must be positioned at the same inclination angles ε and β in a member. The screws must be positioned centrally to the connection force and screwed deep enough so that the screw head is in full contact with the member surface. The minimum pointside penetration depth of the threaded part should be 6d. The members should be compressed together so that no gaps are present 31. LVL suppliers provide their own specific instructions for inclined screw connections with their products. 5.6 BOLTED AND DOWELED CONNECTIONS For bolted and dowelled connections the design rules are defined for connections perpendicular to the grain of the face veneer. The design of LVL connections follows Eurocode 5 Sections 8.5 and 8.6 with the exception of the embedment calculation. The rules for connection geometry are given in Section 5.2 and the rules for wood failure modes in Section 5.3 of this handbook. In laterally loaded connections of bolts and dowels up to 30 mm diameter arranged perpendicular to the grain, the following characteristic embedment strength values should be used for LVL 32: f_(h,k)=(0,082 ∙ (1 - 0,01d) ρ_k)/((k_90 ∙ sin^2 α (k_(C ) 〖∙ cos〗^2 β 〖+ sin〗^2 β) ) (5.39) where ρk is the characteristic density [kg/m³]; α is the angle between load and grain direction; for softwood LVL-C / GLVL-C and α > 45°, α may be assumed as 45°; β is the angle between bolt axis and wide face; d is the bolt diameter [mm]; k90 is 1,15 + 0,015 d for softwood LVL / GLVL; and k_C=max{█(d/( for softwood LVL / GLVL (5.40) 5.7 FASTENING LVL PANELS TO FRAMES Connections of LVL-C panels can be designed according to Eurocode 5 instructions for timber-to-timber connections with commonly available fasteners. The connection capacities and minimum thickness of the frame depend on the panel, fastener and frame material combinations. Capacities and dimension for connections of LVL-C with LVL-P, glulam or solid timber frames are presented in Table 5.5. 5.8 SPECIAL CASES Many nail plate manufacturers have tested the anchoring strength of their products for LVL-P members and the values are of similar levels to C30 structural timber. The values are included in their design software for trusses. LVL bottom cords are used in nail plate trusses to give additional stiffness for the floor part of attic trusses and fire resistance in cases where the rest of the trusses may be exposed to fire. Usually the anchoring devices are fastened to bracing panels with laterally loaded connections to the wide face of the LVL panels. However, glued-in rod or glued-in screw connections on the edge face of LVL panels can be an efficient solution for anchoring large bracing panels. They however require separate type testing and production quality assurance and, in some countries, also separate product certification. Glued-in rod or glued-in screw connections at the edge face require a panel thickness of at least 66 mm to fulfil the edge distance requirement of the connection. h,k = 0,082 ∙ (1 − 0,01 ) k ( 90 ∙ sin2 + cos2 ) ∙ ( ∙ cos2 + sin2 ) C =max� ( −2) 1,15 for softwood LVL / GLVL =max� 5 (10 −30) k 400 (5.34) 189 (255) Members should be pre-drilled when the diameter d of the screw exceeds 8 mm or the diameter of the smooth shank ds exceeds 6 mm. The diameter of pre-drilled holes for nonself-drilling screws should be D = 0.5d - 0.7d, but not more than the inner diameter of the threaded part di. The thickness of the member should be at least: =max{ 5 (10 − 30) k 400 (5.38) where ρk is the characteristic density [kg/m3]; and d is the screw diameter [mm]. General spacings and end and edge distances are presented in Table 5.1. These values are valid for cross screw connections when the compressed and tensioned fasteners of the screw pairs are placed in separate longitudinal rows parallel to the grain, so that the spacing between the rows a2 is 4d and the staggered distance between the screw heads of a screw pair is not more than 3 t1 parallel to the grain. Different types or sizes of screws must not be combined in the same connection. All screws must be positioned at the same inclination angles ε and β in a member. The screws must be positioned centrally to the connection force and screwed deep enough so that the screw head is in full contact with the member surface. The minimum pointside penetration depth of the threaded part should be 6d. The members should be compressed together so that no gaps are present 31. LVL suppliers provide their own specific instructions for inclined screw connections with their products. 5.6 Bolted and doweled connections For bolted and dowelled connections the design rules are defined for connections perpendicular to the grain of the face veneer. The design of LVL connections follows Eurocode 5 Sections 8.5 and 8.6 with the exception of the embedment calculation. The rules for connection geometry are given in Section 5.2 and the rules for wood failure modes in Section 5.3 of this handbook. In laterally loaded connections of bolts and dowels up to 30 mm diameter arranged perpendicular to the grain, the following characteristic embedment strength values should be 32: h,k = 0,082 ∙ (1 − 0,01 ) k ( 90 ∙ sin2 + cos2 ) ∙ ( ∙ cos2 + sin2 ) (5.39) where ρk is the characteristic density [kg/m³]; α is the angle between load and grain direction; for softwood LVL-C / GLVL-C and α > 45°, α may be assumed as 45°; β is the angle between bolt axis and wide face; d is the bolt diameter [mm]; k90 is 1,15 + 0,015 for softwood LVL / GLVL; and 156 LVL Handbook Europe
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