Double angle tension member 300 kN

Assumptions (not given): factored tension 300 kN, E250 steel, M20 bolts of grade 4.6 in double shear (angles on both faces of a 10 mm gusset), $d_0=22$ mm.

1. Bolts

• $V_{dsb}=\dfrac{400}{\sqrt3\times1.25}(245+314)\times10^{-3}=103.3$ kN
• Bearing on gusset ($e=35,\ p=50$): $k_b=0.508$, $V_{dpb}=83.2$ kN → bolt value $83.2$ kN
• $n=300/83.2=3.6$ → 4 bolts (pitch 50, end 35 mm); capacity $333.0$ kN.

2. Section

$A_g\ge\dfrac{300\times1.10}{250}\times10^3=1320$ mm². Try 2 ISA 75×75×6 ($2\times866=1732$ mm²), bolt gauge 40 mm from the heel.

• $T_{dg}=393.6$ kN
• Rupture per angle (150 kN): $A_{nc}=(75-3-22)\times6=300$, $A_{go}=(75-3)\times6=432$ mm², $b_s=w+w_1-t=75+40-6=109$ mm, $L_c=150$ mm, $\beta=0.979$; $T_{dn}=184.7$ kN
• Block shear per angle $=158.2$ kN
• Strength of the pair $=2\times158.2=316.3$ kN $\ge300$ ✓ (block shear governs)

Tack bolts (at no more than 1000 mm) with packing between the angles; $L/r\le400$ is satisfied for members up to about 9 m.

Answer: 2 ISA 75×75×6, one on each side of the gusset, with 4 M20 bolts (4.6) at 50 mm pitch.