To find the resultant force on Bolt R, the problem is broken down into direct shear and torsional shear components caused by the eccentric load.

1. Calculation of Geometric Properties

The total sum of the squared distances of all bolts from the centroid (\( \sum r^2 \)) is calculated using the bolt coordinates:

$$ \sum r^2 = \sum x^2 + \sum y^2 = (6 \times 40^2) + (4 \times 30^2) = 13,200 \text{ mm}^2 $$

2. Force Components on Bolt R

• Direct Shear (\( F_1 \)): The load is distributed equally across all 6 bolts.
  \( F_1 = \frac{P}{n} = \frac{60}{6} = 10 \text{ kN} \) (acting downward).
• Torsional Shear (\( F_2 \)): Caused by the moment \( M = P \times e = 60 \times 100 = 6000 \text{ kN}\cdot\text{mm} \).
  For Bolt R, which is located at a horizontal distance of \( 40 \text{ mm} \) and vertical distance of \( 0 \text{ mm} \) from the centroid:
  \( F_2 = \frac{M \cdot r_R}{\sum r^2} = \frac{6000 \times 40}{13,200} \approx 18.18 \text{ kN} \) (acting downward).

3. Resultant Force

Since both the direct shear and the torsional shear for Bolt R act in the same vertical downward direction, they are simply added:

$$ F_{\text{resultant}} = F_1 + F_2 = 10 + 18.18 = 28.18 \text{ kN} $$

Rounding to one decimal place, the final result is 28.2 kN.