Design load P on SC 250, two brackets

Assumptions: the two bracket plates share the load equally, $P/2$ each. Each bracket has 4 rows of 2 bolts (pitch 60, end distance 40, gauge 120 mm) = 8 bolts M20, grade 4.6, bracket thickness at least 10 mm. The load is in the plane of the bolts at $e=300$ mm from the bolt centroid. The 30 mm off-axis position of $P$ in the section view is assumed to be taken by the column (not by the bolts).

Bolt value (IS 800:2007 cl. 10.3)

• Shear: $V_{dsb}=\dfrac{400}{\sqrt3}\times\dfrac{245}{1.25}\times10^{-3}=45.26$ kN
• Bearing ($e=40$, $p=60$, $t=10$ mm): $k_b=0.606$, $V_{dpb}=99.4$ kN
• Bolt value $=45.26$ kN

Force in the critical bolt per unit load $P_b$ on one bracket

• $\Sigma(x^2+y^2)=8(60^2)+2\times2(30^2+90^2)=64800$ mm²
• Corner bolt ($x=60,\ y=90$): $F_x=\dfrac{P_b\times300\times90}{64800}=0.4167P_b$; $F_y=\dfrac{P_b}{8}+\dfrac{P_b\times300\times60}{64800}=0.4028P_b$
• $R=\sqrt{F_x^2+F_y^2}=0.5795P_b$

Safe load

$$P_b=\frac{45.26}{0.5795}=78.1\ \text{kN per bracket}$$

Answer: $P=2P_b=156.2$ kN (design/factored load for the two brackets together; working value = this / 1.5 if needed).