Structural Timber Design Examples

As stated in 4.3, in order to verify the ultimate and serviceability limit states, each design effect has to be checked and for each effect the largest value caused by the relevant combination of actions must be used.

However, to ensure attention is primarily focussed on the EC5 design rules for the timber or wood product being used, only the design load case producing the largest design effect has generally been given or evaluated in the following examples.

Example 11.12.1 A timber-to-timber tension splice connection in a statically indeterminate structure, which functions in service class 2 conditions in a Category A loaded area (in accordance with EC1991-1-1), is required to connect two 50mm by 100mm members, and is shown in Figure E11.12.1. Two 36 mm by 100 mm side members will be used and the connection will be formed using two type C1 toothed-plate connectors to BS EN 912:2000, diameter dc = 50 mm, spaced 80 mm apart parallel to the grain. The connector bolt is 16 mm in diameter and has a tensile strength of 400 N/mm2. The joint is subjected to a characteristic permanent tensile lateral action of 5.5 kN and a characteristic medium-term variable tensile lateral action of 12.5 kN and all timber is of strength class C22 to BS EN 338:2003.

Confirm that the joint complies with the rules in EC5 and determine the instantaneous and final deflection of the joint at the serviceability limit states (SLS), on the basis that the connection forms part of a structure where the creep behaviour of the connections is different from that of the members.

1. Geometric properties of the joint

Thickness of each side member, t1 t1 = 36 mm

Thickness of central members, t2 t2 = 50 mm

Width of all timber members, h h = 100 mm

Tensile stress area of a bolt, Abt Abt = 157 mm2

Diameter of toothed-plate connector, dc = 50 mm dc (BS EN 912:2000)

Thickness of metal in connector, t t = 1.0 mm

Height of each toothed-plate hc = 13 mm connector, hc

Loaded end distance of the connection, ac3.t = 115 mm ac3jt

Minimum loaded end distance for a acmin3t = 1.1 ■ dc type C1 connector, acmin3.t (equation (11.7); EC5, equation (8.75))

Minimum loaded end distance for the bolt, abmin3t (Table 10.9 (EC5, Table 8.4)) Minimum loaded end distance permitted for this type of connector, a3.t

Angle of loading on the connection relative to the grain, a, in degrees

Bolt spacing parallel to the grain, a\

Minimum bolt spacing parallel to the grain based on Table 11.2, a1c.min abmin3.t = max(7 ■ d, 80 mm)

a3.t = 112 mm The loaded end distance is greater than the minimum distance; therefore OK

a = 0 ■ deg a1 = 80 mm a1c.min = (1.2 + 0.3 cos(a)|) ■ dc a1c.min = 75 mm

Minimum bolt spacing parallel to the aib.t grain based on Table 10.9, a1bmin

Minimum bolt spacing parallel to the grain permitted for this connector, aib .mm

= (4 +| cos(a)j) ■ d a1b.min = 80mm ai.min = max(aib.i

Embedment depth per member, he he =

0 0

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