Code-check of bolts according to Indian standard

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Bolts are checked for shear, bearing, tension capacity and for combined tension and shear.

Shear capacity of bolts

The design strength of the bolt, VdsbV_{dsb}, as governed shear strength is given by IS 800, Cl. 10.3.3:

VsbVdsb V_{sb} \le V_{dsb}

where:

  • Vdsb=Vnsb/γmbV_{dsb} = V_{nsb}/\gamma_{mb} – design shear capacity of a bolt
  • Vnsb=fub3AeV_{nsb} = \frac{f_{ub}}{\sqrt{3}} A_e – nominal shear capacity of a bolt
  • fubf_{ub} – ultimate tensile strength of a bolt;
  • AeA_e – area for resisting shear; Ae=AnA_e = A_n for shear plane intercepted by the threads, Ae=AsA_e = A_s for the case where threads do not occur in shear plane
  • AnA_n – net tensile stress area of the bolt
  • AsA_s – cross-section area at the shank
  • γmb=1.25\gamma_{mb} = 1.25 – partial safety factor for bolts – bearing type – IS 800, Table 5; editable in Code setup

When the grip length of bolts lgl_g (equal to the total thickness of the connected plates) is higher than 5d5d, the design shear capacity VdsbV_{dsb} is reduced by a factor βlg\beta_{lg} – IS 800, Cl. 10.3.3.2:

βlg=83+lg/d  \beta_{lg} = \frac{8}{3+l_g/d}  

According to IS 800, Cl. 10.3.3.3, the design shear capacity of bolts carrying shear through a packing plate with the thickness tpk6t_{pk} \ge 6 mm shall be decreased by a factor:

βpk=(10.0125tpk) \beta_{pk} = (1-0.0125 t_{pk})

Each shear plane is checked separately, and the worst result is shown.

Bearing capacity of bolts

The design bearing strength of a bolt on any plate, as governed by bearing is given by IS 800, Cl. 10.3.4:

VsbVdpb V_{sb} \le V_{dpb}

where:

  • Vdpb=Vnpb/γmbV_{dpb} = V_{npb} / \gamma_{mb} – design bearing strength of a bolt
  • Vnpb=2.5kbdtfuV_{npb} = 2.5 k_b d t f_u – nominal bearing strength of a bolt
  • kb=min{e3d0,p3d00.25,fubfu,1.0}k_b = \min \left \{ \frac{e}{3d_0}, \, \frac{p}{3d_0}-0.25, \, \frac{f_{ub}}{f_u}, \, 1.0 \right \} – factor for joint geometry and material strength
  • ee – end distance of the fastener along bearing direction
  • pp – pitch distance of the fastener along bearing direction
  • fubf_{ub} – ultimate tensile strength of the bolt
  • fuf_u – ultimate tensile strength of the plate
  • dd – nominal diameter of the bolt
  • d0d_0 – diameter of bolt hole
  • tt – plate thickness
  • γmb=1.25\gamma_{mb} = 1.25 – partial safety factor for bolts – bearing type – IS 800, Table 5; editable in Code setup

Bearing on each plate is checked separately and the worst result is shown.


The bearing resistance is reduced for oversized and slotted holes by a factor:

  • 0.7 – for oversized and short slotted holes
  • 0.5 – for long slotted holes

Sizes of oversized, short slotted, and long slotted holes are determined according to IS 800, Table 19.

Tension capacity of bolts

A bolt subjected to a factored tensile force is checked according to IS 800, Cl. 10.3.5:

TbTdb T_b \le T_{db}

where:

  • Tdb=Tnb/γmbT_{db} = T_{nb} / \gamma_{mb} – design tensile capacity of the bolt
  • Tnb=min{0.9fubAn,fybAs(γmb/γm0)}T_{nb} = \min \{ 0.9 f_{ub} A_n, \, f_{yb} A_s (\gamma_{mb} / \gamma_{m0}) \} – nominal tensile capacity of the bolt
  • fubf_{ub} – ultimate tensile strength of the bolt
  • fybf_{yb} – yield strength of the bolt
  • AnA_n – net tensile stress area of the bolt
  • AsA_s – cross-section area at the shank
  • γmb=1.25\gamma_{mb} = 1.25 – partial safety factor for bolts – bearing type – IS 800, Table 5; editable in Code setup
  • γm0=1.1\gamma_{m0} = 1.1 – partial safety factor for resistance governed by yielding – IS 800, Table 5; editable in Code setup

Bolt subjected to combined shear and tension

A bolt required to resist both design shear force and design tensile force at the same time shall according to IS 800, Cl. 10.3.6 satisfy:

(VsbVdb)2+(TbTdb)21.0 \left( \frac{V_{sb}}{V_{db}} \right)^2 + \left( \frac{T_{b}}{T_{db}} \right)^2 \le 1.0

where:

  • VsbV_{sb} – factored shear force
  • Vdb=min{Vdsb,Vdpb}V_{db} = \min \{ V_{dsb}, \, V_{dpb} \} – design shear resistance of the bolt – IS 800, Cl. 10.3.2
  • VdsbV_{dsb} – design shear resistance
  • VdpbV_{dpb} – design bearing resistance
  • TbT_b – factored tensile force
  • TdbT_{db} – design tensile capacity of the bolt

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