Steel structures miscellaneous Easy Questions and Answers | Page - 5

Steel structures miscellaneous

ISA 100 × 100 × 10 mm (Cross sectional area = 1908 mm²) is welded along A and B, such that the lengths of the woeld along A and B are l₁ and l₂, respectively. Which of the following is a possibly acceptable combination of l₁ and l₂.

1. l₁ = 60 mm and l₂ = 150 mm
1. l₁ = 150 mm and l₂ = 60 mm
1. l₁ = 150 mm and l₂ = 150 mm
1. Any of the above, depending on the size of the weld.

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For no eccentricity, the algebraic sum of moments of two welds about centre of gravity must be zero. C.G is B, thus l₂ must be more than l₁

Correct Option: A

For no eccentricity, the algebraic sum of moments of two welds about centre of gravity must be zero. C.G is B, thus l₂ must be more than l₁

In the design of lacing system for a built-up steel column, the maximum allowable slenderness ratio of a lacing bar is

1. 120
1. 145
1. 180
1. 250

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Maximum allowed slenderness ratio of lacing bars is 145.

Correct Option: B

Maximum allowed slenderness ratio of lacing bars is 145.

A truss, as shown in the figure, is carrying 180 kN load at node L₂. The force in the diagonal member M₂U₄ will be

1. 100 kN tension
1. 100 kN compression
1. 80 kN tension
1. 80 kN compression

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Taking moment about L
V_L6 × 24 = 180 × 2 × 4
∴ VL6 = 60 kN
V_L0 = 120 kN
Force in member M₂ L₄ is zero.
Take section along u₃ u₄ – L₃ L₄

Σ v = 0
F_U4M2 cos θ = 60
∴ F_U4M2 = 60
cos θ

= 60 × 5 = 100 kN
3

The force is tension (pulling)

Correct Option: A

Taking moment about L
V_L6 × 24 = 180 × 2 × 4
∴ VL6 = 60 kN
V_L0 = 120 kN
Force in member M₂ L₄ is zero.
Take section along u₃ u₄ – L₃ L₄

Σ v = 0
F_U4M2 cos θ = 60
∴ F_U4M2 = 60
cos θ

= 60 × 5 = 100 kN
3

The force is tension (pulling)

A streel portal frame has dimensions, plastic moment capacities and applied lads as shown in the figure. The vertical load is always twice of the horizontal load. The collapse load P required for the development of abbeam mechanism is

1. 3M_p /L
1. 4M_p /L
1. 6M_p /L
1. 8M_p /L

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Internal work done,
w_i = M_p θ + 2 M_p. θ + 2 M_p θ + M_p θ
= 6 M_p θ
External work done,
W_e = load × Δ
= 2 Pδ
= 2PLθ
W_i = W_e
6M_pθ = 2P Lθ
∴ P = 3m_p
L

Correct Option: A

Internal work done,
w_i = M_p θ + 2 M_p. θ + 2 M_p θ + M_p θ
= 6 M_p θ
External work done,
W_e = load × Δ
= 2 Pδ
= 2PLθ
W_i = W_e
6M_pθ = 2P Lθ
∴ P = 3m_p
L

The permissible stress in axial tension s_st in steel member on the net effective area of the section shall not exceed the following value (f_y is the yield stress)

1. 0.80f_y
1. 0.75f_y
1. 0.60f_y
1. 0.50f_y

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Permissible stress = 0.6 f_y.

Correct Option: C

Permissible stress = 0.6 f_y.