Uuuuuuuuuu

Fig. 4.11. Beams with an end notch.

to beams with a notch on the opposite side to the support where the contribution within a distance of hef from the edge may be ignored (Figure 4.10b). No reduction is permitted when the notch is on the same side as the support (Figure 4.11). • /v,d is the design shear strength and is defined as:

Km where kmod, ksys, KM are as described in Section 4.5.1.1 and

/v,k is the characteristic shear strength. The strength is based on the shear strength parallel to the grain (as this is smaller than the shear strength perpendicular to the grain) and for softwood has in general been derived from the bending strength of the species, being the minimum of 3.8 N/mm2 or 0.2(/m,k)0 8, where /m,k is the characteristic bending strength of the timber [2]. Values for the shear strength of timber and wood-based structural products are given in Chapter 1. kv is a factor that takes account of the effect of a notch in the beam. Stress concentrations are generated by a notch, and from the application of linear elastic fracture mechanics combined with experimental testing, values for the factor have been derived to remove the risk of beam failure due to the effect of crack propagation. For beams with a notch, EC5, 6.5.2, requires the following: where the notch is on the opposite side to the support (see Figure 4.10b), kv = 1.0; where the notch on the same side as the support (see Figure 4.11), kv is the lesser of:

kn (1 + 1.1/L5/Vh) kv =-, V -----v and ky = 1 (4.19)

where:

/ is the inclination of the notch and is 0 for a right angle notch, h is the beam depth in mm, x is the distance from the centroid of the support reaction to the corner of the notch in mm, kn is a factor that equals 4.5 for LVL, 5.0 for solid timber (6.5 for glued-laminated timber):

4.5.2.2 Shear stress with both stress components perpendicular to the grain (rolling shear) For a rectangular section with both shear stress components perpendicular to the grain, where the design shear force, Vd, is applied over length b, as shown in Figure 4.12, the validation requirement for the design shear stress, rd, will be:

< /v,d (EC5, equat/on (6.13)) (4.17) where /v,d is the design shear strength of the member and is defined as

0 0

Post a comment