Reference Standards Group

ti/t2

Figure 3.5: Factor ß asa function of the thickness ratio of the connected plates

tl / h

ß

tb,resin

>2,0 1,0 < ti / t2 < 2,0 <1,0

1,66 - 0,33 (t1 / t2) 1,33

2 t2 < 1,5 d tx < 1,5 d ti < 1,5 d

Figure 3.6: Limiting effective length for long injection bolts

3.7 Group of fasteners

(1) The design resistance of a group of fasteners may be taken as the sum of the design bearing resistances -Fb,Rd of the individual fasteners provided that the design shear resistance ^v,Rd of each individual fastener is greater than or equal to the design bearing resistance -Fb,Rd . Otherwise the design resistance of a group of fasteners should be taken as the number of fasteners multiplied by the smallest design resistance of any of the individual fasteners.

3.8 Long joints

(1) Where the distance Gj between the centres of the end fasteners in a joint, measured in the direction of force transfer (see Figure 3.7), is more than 15 d, the design shear resistance GvRd of all the fasteners calculated according to Table 3.4 should be reduced by multiplying it by a reduction factor /?Lf, given by:

15 d

200 d

(2) The provision in 3.8(1) does not apply where there is a uniform distribution of force transfer over the length of the joint, e.g. the transfer of shear force between the web and the flange of a section.

Figure 3.7: Long joints

3.9 Slip-resistant connections using 8.8 or 10.9 bolts 3.9.1 Design Slip resistance

(1) The design slip resistance of a preloaded class 8.8 or 10.9 bolt should be taken as:

7m 3

where:

ks is given in Table 3.6 n is the number of the friction surfaces

U is the slip factor obtained either by specific tests for the friction surface in accordance with 2.8 Reference Standards: Group 7 or when relevant as given in Table 3.7.

(2) For class 8.8 and 10.9 bolts conforming with 2.8 Reference Standards: Group 4, with controlled tightening in conformity with 2.8 Reference Standards: Group 7, the preloading force ApC to be used in equation (3.6) should be taken as:

Table 3.6: Values of ks

Description

ks

Bolts in normal holes.

1,0

Bolts in either oversized holes or short slotted holes with the axis of the slot perpendicular to the direction of load transfer.

0,85

Bolts in long slotted holes with the axis of the slot perpendicular to the direction of load transfer.

0,7

Bolts in short slotted holes with the axis of the slot parallel to the direction of load transfer.

0,76

Bolts in long slotted holes with the axis of the slot parallel to the direction of load transfer.

0,63

Table 3.7: Slip factor, p, for pre-loaded bolts

Class of friction surfaces (see 2.8 Reference Standard: Group 7)

Slip factor ju

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