Bolts

The tension resistance of the bolt Ft,Rd is provided in EN1993-1-8 Table 3.4:

Ft,Rd = k2 ⋅ fub ⋅ As / γM2

where:

• k2 is a coefficient that takes values k2 = 0.63 for countersunk bolts or k2 = 0.9 otherwise.

• fub is the ultimate tensile strength of the bolt depending on the bolt class (see table above).

• As is the nominal tensile stress area of the bolt.

• γM2 is the partial safety factor for the resistance of bolts in accordance with EN1993-1-8 §2.2(2) Table 2.1 and the National Annex. The recommended value in EN1993-1-8 is γM2 = 1.25.

The shear resistance of the bolt per shear plane Fv,Rd is provided in EN1993-1-8 Table 3.4:

Fv,Rd = αv ⋅ fub ⋅ A / γM2

where:

• αv is a coefficient that takes values αv = 0.6 for bolt classes 4.6, 5.6, 8.8 or αv = 0.5 for bolt classes 4.8, 5.8, 6.8 and 10.9. When the shear plane passes through the unthreaded part of the bolt αv = 0.6.

• fub is the ultimate tensile strength of the bolt depending on the bolt class (see table above)

• A is the appropriate area for shear resistance. When the shear plane passes through the threaded part of the bolt A is equal to the tensile stress area of the bolt As. When the shear plane passes through the unthreaded part of the bolt A is equal to the gross cross-sectional area of the bolt Ag.

• γM2 is the partial safety factor for the resistance of bolts in accordance with EN1993-1-8 §2.2(2) Table 2.1 and the National Annex. The recommended value in EN1993-1-8 is γM2 = 1.25.

The interaction between shear and tension is expressed in EN1993-1-8 Table 3.4 according to the following linear relation:

Fv,Ed / Fv,Rd + (Ft,Ed / Ft,Rd) / 1.4 ≤ 1.0

where:

• Fv,Ed is the applied shear load and Fv,Rd is the shear resistance of the bolt.

• Ft,Ed is the applied tensile load and Ft,Rd is the tension resistance of the bolt.

The bearing resistance of the bolt Fb,Rd should be verified against the applied shear load Fv,Ed in accordance with EN1993-1-8 Table 3.4:

Fb,Rd = k1 ⋅ αb ⋅ fu ⋅ d ⋅ t / γM2

where:

• fu is the ultimate tensile strength of the connected plate

• d is the nominal diameter of the bolt.

• t is the thickness of the connected plate.

• γM2 is the partial safety factor for the resistance of bolts in accordance with EN1993-1-8 §2.2(2) Table 2.1 and the National Annex. The recommended value in EN1993-1-8 is γM2 = 1.25.

The coefficient k1 is:

for edge bolts: k1 = min( 2.8⋅e2/d0 - 1.7, 1.4⋅p2/d0 - 1.7, 2.5 )

for inner bolts: k1 = min( 1.4⋅p2/d0 - 1.7, 2.5 )

where e2 is the distance between the center of the edge bolt and the end of the plate measured perpendicular to the load transfer direction, p2 is the distance between the centers of neighboring bolts measured perpendicular to the load transfer direction, and d0 is the diameter of the bolt hole.

The coefficient αb is:

αb = min( αd, fub/fu, 1.0 )

for end bolts: αd = e1/(3⋅d0)

for inner bolts: αd = p1/(3⋅d0) - 1/4

where e1 is the distance between the center of the end bolt and the end of the plate measured parallel to the load direction, p1 is the distance between the centers of neighboring bolts measured parallel to the load direction, and d0 is the diameter of the bolt hole.

Therefore, based on the equations above, the bearing resistance of the bolt Fb,Rd is not affected by the distances e1, p1, e2, p2 when the following conditions are satisfied:

for edge bolts: e1 ≥ 3.0⋅d0 and e2 ≥ 1.5⋅d0

for inner bolts: p1 ≥ 3.75⋅d0 and p2 ≥ 3.0⋅d0

The punching resistance of the bolt Bp,Rd should be verified against the applied tensile load Ft,Ed in accordance with EN1993-1-8 Table 3.4:

Bp,Rd = 0.6⋅π ⋅ dm ⋅ tp ⋅ fu / γM2

where:

• dm is the mean of the across points and across flats dimensions of the bolt head or the nut, whichever is smaller.

• tp is the plate thickness under the bolt or nut.

• fu is the ultimate tensile strength of the steel plate.

• γM2 is the partial safety factor for the resistance of bolts in accordance with EN1993-1-8 §2.2(2) Table 2.1 and the National Annex. The recommended value in EN1993-1-8 is γM2 = 1.25.

The value of the mean diameter dm is estimated as follows. The distance across flats s of the nut is given in the standard ISO 898-2. By approximately ignoring the corner rounding for a perfect hexagon the relation of the distance across points s' and the distance across flats s is s' = s / cos(30°) = 1.1547⋅s. Therefore the mean diameter dm is approximately:

dm = (s + 1.1547⋅ s) / 2 = 1.07735⋅s