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Method of Analysis BS 449 Part 2

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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:

P_s = p_s A_s

where

p_s is the shear strength from Clause 50b and Table 20 of the BS449, and
A_s 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:

P_bb = d t p_bb

where

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
p_bb 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 P_bs is calculated as:

P_bs = d t p_bs<= e t p_bs /2

where

p_bs is the bearing strength of the connected parts obtained from Table 20A of BS 449.

The tension capacity P_t 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:

P_t = p_t A_t

where

p_t is the tension strength obtained from Clause 50b and Table 20 of the code of BS 449, and

A_t 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:

F_s = (1.4 - F_t /P_t ) P_s<= P_s

where F t is the applied external tension and _t , P_s are as defined in the above. When the shear plane lies in the shank length, P_t is Tension Capacity of the shank length. When the shear plane lies in the threaded length, P_t is Tension Capacity based on tensile stress area of the bolt.