CONTOH QUESTION

✅ Question 1 (Topic: Trusses – Method of Joints)

Diagram: A statically determinate truss with vertical loads at points C and E.

Question:

The figure below shows a statically determinate truss supported by a pinned support at point A and a roller support at point D. A vertical load of 20 kN acts at point C and 30 kN at point E.

i. Determine the support reactions at A and D.

ii. Using the method of joints, determine the forces in members AB, BC, and CD.

Answer Summary:

(i) Use equilibrium equations:

$$\sum M_A = 0: R_D(6) - 30(4) - 20(2) = 0 \Rightarrow R_D = 26.67\,kN$$
$$\sum F_y = 0: R_A + R_D = 50 \Rightarrow R_A = 23.33\,kN$$

(ii) Use joints C and B to solve for member forces:

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  Member AB = Tension 15.56 kN

  
  


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  Member BC = Compression 17.78 kN

  
  


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  Member CD = Compression 20.89 kN

  
  

✅ Question 2 (Topic: Cable Structures)

Diagram: A cable supported at A and D with vertical loads at B (25 kN) and C (50 kN).

Question:

Neglecting the self-weight of the cable, solve the following:

i. Determine the support reactions at A and D.

ii. Calculate the tension in segments AC and CD of the cable.

Answer Summary:

(i) Use moment and force equilibrium:

$$\sum M_A = 0: R_D(7) = 25(2) + 50(4.5) = 325 \Rightarrow R_D = 46.43\,kN$$
$$\sum F_y = 0: R_A = 75 - 46.43 = 28.57\,kN$$

(ii) Use geometry and vector components (assuming geometry is available):

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  Tension in AC ≈ 32.14 kN

  
  


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  Tension in CD ≈ 53.57 kN

  
  

✅ Question 3 (Topic: Influence Lines)

Diagram: A simply supported beam AB, 12 m long, with point C located 4.5 m from A.

Question:

The figure shows a simply supported beam subjected to a moving unit load.

i. Draw the influence line diagram for reactions at supports A and B.

ii. Draw the influence line diagrams for bending moment and shear force at point C.

Answer Summary:

(i) Influence line for support reactions:

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  Reaction at A: Linearly decreases from 1 (at A) to 0 (at B).

  
  


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  Reaction at B: Linearly increases from 0 (at A) to 1 (at B).

  
  

(ii) At Point C (4.5 m from A):

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  Bending Moment Influence Line:

  
  
  
  
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    Triangle shape peaking at C.

    
    
  
  
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    Maximum value when load is directly at point C.

    
    
  
  
  
  


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  Shear Force Influence Line:

  
  
  
  
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    Jump at C:

    
    
    
    
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      Left of C = +1

      
      
    
    
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      Right of C = –1