10.3Bearing Type Bolts

10.3.1 Effective Areas of Bolts

10.3.2

A bolt subjected to a factored shear force ( $V_{\mathrm{sb}}$ shall satisfy the condition

$V_{\mathrm{sb}}=V_{\mathrm{db}}$

where $V_{\mathrm{db}}$ is the design strength of the bolt taken as the smaller of the value as governed by shear, $V_{\mathrm{dsb}}$ (see 10.3.3) and bearing, $V_{\mathrm{dpb}}$ (see 10.3.4).

10.3.3 Shear Capacity of Bolt

The design strength of the bolt, $V_{\mathrm{dsb}}$ as governed shear strength is given by:

$V_{\mathrm{dsb}}=V_{\mathrm{nsb}} / \gamma_{\mathrm{mb}}$

where

$\begin{aligned} V_{\mathrm{nsb}} & =\text { nominal shear capacity of a bolt } \\ & \text { calculated as follows: }\end{aligned}$

$V_{\mathrm{nsb}}=\frac{f_{\mathrm{u}}}{\sqrt{3}}\left(n_{\mathrm{n}} A_{\mathrm{nb}}+n_{s} A_{s b}\right)$

where

$f_{\mathrm{u}}=$ ultimate tensile strength of a bolt.

• $n_{\mathrm{n}}=$ number of shear planes with thread intercepting the shear plane;

$\begin{aligned} n_{\mathrm{s}} & =\text { number of shear planes without threads } \\ & \text { intercepting the shear plane; }\end{aligned}$

$A_{\mathrm{sb}}=$ nominal plain shank area of the bolt; and

• $A_{\mathrm{nb}}$ = net shear area of the bolt at threads, may be taken as the area corresponding to root diameter at the thread.

10.3.4 Bearing Capacity of the Bolt

The design bearing strength of a bolt on any plate, $V_{\text {dpb }}$ as governed by bearing is given by:

$V_{\mathrm{dpb}}=V_{\mathrm{npl}} / \gamma_{\mathrm{mb}}$

where

vnpb = nominal bearing strength of a bolt = 2.5 k~ d tfu

where

$k_{\mathrm{b}}$ is smaller of $\frac{e}{3 d_{0}}, \frac{p}{3 d_{0}}-0.25, \frac{f_{\mathrm{ub}}}{f_{\mathrm{u}}}, 1.0$;

$e, p$ = end and pitch distances of the fastener along bearing direction;

$d_{0}=$ diameter of the hole;

• $\begin{aligned} f_{\mathrm{ub}}, f_{\mathrm{u}} & =\text { ultimate tensile stress of the bolt and the } \\ & \text { ultimate tensile stress of the plate, } \\ & \text { respectively; }\end{aligned}$
• $d=$ nominal diameter of the bolt; and
• $t=$ summation of the thicknesses of the connected plates experiencing bearing stress in the same direction, or if the bolts are countersunk, the thickness of the plate minus one half of the depth of countersinking.

The bearing resistance (in the direction normal to the slots in slotted holes) of bolts in holes other than standard clearance holes may be reduced by multiplying the bearing resistance obtained as above, $V_{\mathrm{npb}}$, by the factors given below:

• a) Over size and short slotted holes – 0.7, and
• b) Long slotted holes - 0.5.

NOTE - The block shear of the edge distance due to bearing force may be checked as given in 6.4.

10.3.5 Tension Capacity

A bolt subjected to a factored tensile force, $T_{\mathrm{b}}$ shall satisfy:

$T_{\mathrm{b}} \leq T_{\mathrm{db}}$

where

$\begin{aligned} T_{\mathrm{db}} & =T_{\mathrm{nb}} / \gamma_{\mathrm{mb}} \\ T_{\mathrm{nb}} & =\text { nominal tensile capacity of the bolt, } \\ & \text { calculated as: }\end{aligned}$ $0.90 f_{\mathrm{ub}} A_{\mathrm{n}}<f_{\mathrm{yb}} A_{\mathrm{sb}}\left(\gamma_{\mathrm{mb}} / \gamma_{\mathrm{m} 0}\right)$

where

$f_{\mathrm{ub}}=$ ultimate tensile stress of the bolt.

$f_{\mathrm{yb}}=$ yield stress of the bolt,

$A_{\mathrm{n}}=$ net tensile stress area as specified in the appropriate Indian Standard (for bolts where the tensile stress area is not defined, $A_{\mathrm{n}}$ shall be taken as the area at the bottom of the threads), and

$A_{\mathrm{sh}}=$ shank area of the bolt.

10.3.6 Bolt Subjected to Combined Shear and Tension

A bolt required to resist both design shear force (Vsd) and design tensile force (Tb) at the same time shall satisfy:

$\left(\frac{V_{\mathrm{sb}}}{V_{\mathrm{db}}}\right)^{2}+\left(\frac{T_{\mathrm{b}}}{T_{\mathrm{db}}}\right)^{2} \leq 1.0$

where

• $V_{\mathrm{sb}}=$ factored shear force acting on the bolt.

=

• $V_{\mathrm{db}}=$ design shear capacity (see 10.3.2)
• $T_{\mathrm{b}} \quad=$ factored tensile force acting on the bolt, and
• $T_{\mathrm{db}}=$ design tension capacity (see 10.3.5)