Lug Angle Connection:

Design an end connection for an ISA 150 × 75 × 10 tension member using lug angles and 20 mm dia rivets. The gusset plate is 16 mm thick. Permissible stresses are:

Shear stress in rivets (τ_vf) = 100 MPa

Bearing stress in rivets (σ_pf) = 300 MPa

Allowable tensile stress in steel = 150 MPa

Solution

Rivet hole diameter = 20 +1.5 = 21.5 mm

Gross area of ISA 150 × 75 × 10, A_g = 2160 mm²

Net area of member (deducting one rivet hole)

= 2160 - 21.5 × 10 = 1945 mm²

Strength of member = 1945 × 150 = 291, 750 N

Area of unconnected (outstanding), e.g. = ( 75 - 10/2)) × 10 = 700 mm²

Strength of unconnected leg = 700 × 150 = 105000 N

Strength of connected leg = 291750 - 105000 = 186750 N

Strength of lug angle = 1.2 × Strength of unconnected leg

= 1.2 × 105000 = 126000 N.

∴ Net area of lug angle = 126000/150 = 840 mm ²

∴ Try ISA 75 × 75 × 8 giving gross area = 1140 mm² and net area = 1140 - 21.5 × 8 = 968 mm2 > 840 mm² ∴ OK.