Question

A rigid bar of negligible weight is supported by steel and aluminium bars as shown in Fig. 2.14. It carries a load W = 60kN. Determine the temperature change that will cause the stress in the steel bar to be 50 N/mm² . α_S = 11 × 10⁻⁶ /°C, α_A = 22 × 10⁻⁶ /°C, E_S = 3E_A = 210 kN/mm².

Answer 1

Due to the combined effect of load and temperature change, the final stress in the steel wire is 50N/mm² 

Area of cross-section, 

AS = 300 mm² 

Load WS in the steel bar = 300 × 50 = 15,000 

N = 15 kN 

Taking moments of forces about point A, 

W_S × 1 − 2 × 60 + W_A × 3 = 0