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Steel Designers' Manual - 6th Edition (2003)
when the flange is very stiff, with no plastic deformation so that its flexural deformation
is small relative to the elongation of the bolts, will the prying forces be
insignificant.
In BS5950-1: 2000 the tension capacity of a connection using bolts (including 90°
countersunk head bolts) may be checked using either a simple method (clause
6.3.4.2), which includes an allowance for prying forces, or a more exact method
(clause 6.3.4.3) which explicitly accounts for prying action. The simple method may
only be used in a connection where the cross-centre spacing of the bolt lines does
not exceed 55% of the flange width or end-plate width. When using the simple
method, if a connected part is designed assuming double curvature bending, its
moment capacity per unit width should be restricted to the elastic resistance, pytp 2 /6,
where tp is the thickness of the connected part. In the simple method the prying force
need not be calculated but the tensile force per bolt, Ft, transmitted by the connection
should not exceed the nominal tension capacity Pnom of the bolt, obtained from
Pnom = 0.8ptAt, where At is the tensile stress area as specified in the appropriate bolt
standard. For bolts where the tensile stress area is not defined, At should be taken
as the area at the bottom of the threads and pt is the tension strength of the bolt
obtained from Table 34.
The more exact method may be used for a connection in which both of the connected
parts satisfy one or more of the following:
(a) the connected part spans between two or more supporting parts;
(b) the outstand of the connected part is designed assuming single curvature
bending;
(c) the outstand of the connected part is designed assuming double curvature
bending and the resulting prying force Q is calculated and included in the total
applied tension Ftot in the bolt;
(d) the connected part spans between two or more supporting parts in one direction,
but acts as an outstand in the other direction, and the resulting prying force
Q is calculated and included in the total applied tension Ftot in the bolt.
In cases (a) and (b) no prying force is necessary for equilibrium. In the more exact
method the moment capacity per unit width of the connected part should be taken
as the plastic resistance, pytp 2 /4, and the total applied tension Ftot in the bolt, including
the calculated prying force, should not exceed the tension capacity Pt, taken as
ptAt.
25.4 Plates loaded in-plane
25.4.1 Deductions for holes
Plates loaded in-plane 717
Where holes are staggered the effective net section through the line of the holes is
taken as the area of the gross cross section less a deduction of the area of the holes
in any (zig-zag) section less s 2 t/4g for each gauge space in the line of holes (Fig.