Bolted Connections MCQ with answer and solution

Concept

Bearing strength of a bolted connection depends on the bolt diameter, thickness of the connected member (or gusset plate), and the bearing stress.

Formula

P_b = d × t × f_p

Step-by-step solution

1. Identify the given parameters: Bolt diameter (d) = 16 mm, Thickness of gusset plate = 5 mm, Thickness of angle leg = 6 mm. 2. Determine the critical thickness (t) for bearing: minimum of gusset plate and angle leg thickness = min(5 mm, 6 mm) = 5 mm. 3. Identify the allowable bearing stress (f_p) = 250 MPa (or N/mm²). 4. Calculate the bearing strength: P_b = d × t × f_p = 16 mm × 5 mm × 250 N/mm² = 20,000 N = 20 kN.

Explanation

According to IS 800:2007, the bearing strength of a bolt is given by V_pb = 2.5 × d × t × f_u / γ_mb. However, when specific allowable bearing stress is given instead of ultimate tensile stress, bearing strength is calculated as P_b = d × t × σ_pb. Here, d = 16 mm, t = min(plate thickness, angle thickness) = min(5 mm, 6 mm) = 5 mm, and allowable bearing stress = 250 MPa.

Why the other options are wrong

A: Calculation error or incorrect area. C: Incorrect thickness or stress multiplication. D: Arithmetical error in standard formula.

Shortcut

Remember that bearing strength is projected area (d × t) multiplied by the bearing stress.

Common mistake

Taking the thickness of the angle leg (6 mm) instead of the gusset plate (5 mm) when checking bearing on the gusset plate, or vice versa if checking the angle.