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Method of Analysis BS 449 Part 2
Method of Analysis Equations BS 449: Part 2
The method of analysis based on BS449: Part 2 and is described below.
Ordinary Bolts: Grades 4.6, 6.8, 8.8, 10.9, 12.9 and 14.9
The shear capacity P s is calculated as:
Ps = ps As
ps is the shear strength from Clause 50b and Table 20 of the BS449, and
As is the Shank or Tensile Stress Area of the bolts as specified in respective British Standards.
The bearing capacity is taken as lesser of the bolt bearing capacity P bb and the connected ply bearing capacity P bs . The bolt bearing capacity P bb is calculated as:
Pbb = d t pbb
d is the nominal bolt diameter,
t is the thickness of the connected ply, or if the bolts are countersunk, the thickness of the ply minus half the depth of countersinking, which is equal to half the nominal diameter of bolts, and
pbb is bearing strength of the bolt obtained from Clause 50b and Table 20 of BS449.
Depending upon the end distance e of the bolt hole to the ply edge described in the range 2d to 1.25d, the bearing capacity of the connected ply Pbs is calculated as:
Pbs = d t pbs<= e t pbs /2
pbs is the bearing strength of the connected parts obtained from Table 20A of BS 449.
The tension capacity Pt of the bolt is calculated both for the Shank Length and the Threaded Length. The Shank Length capacity is based on nominal diameter of the bolt and its use is relevant in combined Tension and Bending only, when shear plane lies in the shank length. The Threaded length capacity is based on tensile stress area of threads and is the critical strength in direct tension and combined Tension and Bending when shear plane lies in the threaded length. The equation is:
Pt = pt At
pt is the tension strength obtained from Clause 50b and Table 20 of the code of BS 449, and
At is the shank or tensile stress area as specified in respective British Standards.
Combined Tension and Shear
For any bolt diameter, the Combined Tension and Shear Capacity is calculated by typing a value in the cell for Applied Tension in its row. When subjected to both Tension and Shear, the combination shear capacity F s is given by:
Fs = (1.4 - Ft /Pt ) Ps<= Ps
where F t is the applied external tension and t , Ps are as defined in the above. When the shear plane lies in the shank length, Pt is Tension Capacity of the shank length. When the shear plane lies in the threaded length, Pt is Tension Capacity based on tensile stress area of the bolt.
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