Panel arrangement 2

and acts as a deep beam between end supports along lines A-A when subjected to lateral loading as shown.

To be able to apply the simplified method given in EC5 the following conditions have to apply:

(a) The span t must lie between 2b and 6b.

(b) The design condition at the ULS must be by failure of the fasteners and not failure of the beams or panels.

(c) The panels are fixed to their supports. All unsupported edges shall be fixed to adjacent panels as defined in EC5, 10.8.1. The fixings shall be screws or nails (other than smooth nails) compliant with EN 14592 [5] and the maximum spacing along the panel edges shall be 150 mm and 300 mm along the supports.

9.4.2 Simplified design procedure

The diaphragm must be checked for bending, shear and for the lateral design strength of the fixings of the structure to the supporting timber frame along lines A-A. The design procedures are given for the condition where there is a design lateral load, Fd, along length I of the diaphragm as shown in Figure 9.7 and the diaphragm width is b.

(a) Bending strength (assuming that the edge beams are supported vertically and they only have to resist the effects of the lateral loading).

All of the bending is assumed to be taken by the edge beams and consequently they must be continuous or detailed to be able to transfer the tensile/compression loading at adjacent sections. For the condition where the edge beam is continuous, has a width w (mm) and depth h (mm), the weaker strength will be its tensile strength and the condition to be satisfied will be

where the symbols are as defined above and:

• /t,o,d is the design tension strength of the timber or wood-based material in the edge beam and will be obtained from:

• kmod is the modification factor for load duration and service classes as given in Table 2.4.

where:

• kh is the size effect modification factor for members under tension, as discussed in Chapter 2. It is referred to in Table 2.11 and the largest cross-sectional dimension of the member should be used to evaluate the factor. When dealing with LVL, the factor is defined as kt, and is associated with member length.

• Ym is the partial coefficient for material properties, given in Table 2.6.

• /t,o,k is the characteristic tensile strength of the timber or wood-based product parallel to the grain. Strength information for timber and the commonly used wood-based structural products is given in Chapter 1.

(b) Shear strength o/the diaphragm along edges A-A.

All of the shear must be taken by the panel material. The shear stress is assumed to be uniform across the width of the diaphragm and where the panel material is t (mm) thick, the condition to be satisfied will be:

where the symbols are as defined above and:

• where /v , d is the design panel shear strength of the panel material and will be obtained from:

• /v , k is the characteristic panel shear strength of the timber or wood-based product. Strength information for timber and the commonly used wood-based structural products is given in Chapter 1.

(c) Lateral strength o/the panel to support structure fixings along edges A-A.

The end reactions in the diaphragm must be transferred to the supporting structure by the fasteners which secure the panels to the structure. Where the detailing at each end is the same and the fasteners are at a spacing of s (mm) along the length of the support, the condition to be satisfied will be: Fd Rdb

2 skpanel where the functions are as described above and:

• Rd is the design lateral strength of a fastener.

• kpanei is 1.0 where adjacent panel edges are nailed or screwed to the same supporting batten, or where adjacent panel edges are joined by glued tongue and grooved joints, and it is 1.5 where tongued and grooved panel edges are not supported by battens and are not glued.

(a) Wall diaphragm (b) Racking resistance (c) Overturning

Fig. 9.8. Wall diaphragm resisting racking loads.

(a) Wall diaphragm (b) Racking resistance (c) Overturning

Fig. 9.8. Wall diaphragm resisting racking loads.

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