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(a) Connection

Fig. 12.8. Shear force analysis of member 2 subjected to moment Md per shear plane.

(a) Connection

Fig. 12.8. Shear force analysis of member 2 subjected to moment Md per shear plane.

The summation of the horizontal component of the forces in the fasteners in each row k acting perpendicular to the grain in member 2 arising from the design moment, Md, will be:

ff max max where the functions are as previously defined, and FM hjd,k is the horizontal shear force per shear plane in row k in the zone arising from the applied moment Md and nk is the number of fasteners per shear plane in row k.

Member 2

Member 1

Fastener i

Member 2

Member 1

Fastener i

If the connection is now subjected to the horizontal design force, Hd, in accordance with the assumption in 12.5.1(b), the horizontal lateral force taken by each fastener in the shear plane, FH,h,d, shown in Figure 12.7, will be:

Although there will be vertical forces in the fasteners due to the vertical design force Vd, these will not influence the horizontal shear force and need not be considered. The horizontal design shear force per shear plane on member 2, FH,h,d, will be the maximum shear force in the zone. It is obtained by starting at the bottom line in the zone and progressively evaluating the cumulated shear force within the zone. The maximum value will depend on the fastener configuration and the value of the applied horizontal shear force. For the case shown in Figure 12.5 the maximum value, FH,h,d, will be as follows:

• In the first row of fasteners,

• In the second row of fasteners,

In the third row of fasteners,

rmax n

• The maximum value will be

(Note that the first row is the row furthest from the centroid, the second row is next closest to the centroid, and the third row is the row closest to the centroid. For connections with greater numbers of rows of fasteners, the process is extended to cover all of the rows in the zone.)

In equation (12.25) n is as defined in equation (12.16) and the number of fasteners in the shear plane in each row is nr1 in the first row, nr2 in the second row and nr3 in the third row.

As for member 1, since no guidance is given in EC5 to enable the splitting capacity of member 2 to be checked, the shear strength of the member within the boundary area of the connection should be checked as follows:

3 KM, connection where the member thickness is b (mm) and the depth is h (mm) and the other symbols are as previously defined.

It should be noted that if there are nsp shear planes in the connection (e.g. in a three-member connection formed by another member 1 fastened to the other face of member 2 using the same fastener configuration, nsp = 2), the design force to be taken by member 2 will be the force per shear plane multiplied by nsp.

12.5.3.2 Force component checks in a row of fasteners parallel to the grain

As stated in 12.3, where the fastener configuration in a connection is such that:

(a) no row exists where a force component from two or more fasteners in the row is parallel to the grain in any of the connected members, or,

(b) there are rows where the above situation will arise but the spacing between the fasteners parallel to the member grain complies with the criteria given in Table 12.2, the full number of fasteners in the connection can be used.

However, where the above criteria are not met EC5 rules require that where a row of fasteners is acted on at an angle to the grain, it must be verified that the force component parallel to the row will be less than or equal to the load-carrying capacity of the row based on the use of the effective number of fasteners in the row, nef. The effective number of fasteners is defined in Chapter 10 for metal dowel type fasteners and in Chapter 11 for connectors.

For this situation, the reduced capacity of each fastener in a row will be obtained by multiplying the design lateral capacity of the fastener when loaded parallel to the grain by nef/n and the result must be shown equal to or greater than the value of fastener force component in the row acting parallel to the grain.

Consider, for example, a connection subjected to combined moment and lateral forces where the design forces in a row of fasteners in member 1 are as shown in Figure 12.10. The force in fastener i, Fi>d, will have the following value of component acting parallel to the grain:

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