Multiple choice

A three-hinged parabolic arch ABC has a span of 20 m and a central rise of 4 m. The arch has hinges at the ends at the centre. A train of two point loads of 20 kN and 10 kN, 5 m apart, crosses this arch from left to right, with 20 kN load leading. The maximum thrust induced at the supports is

  1. 25.00 kN

  2. 28.13 kN

  3. 31.25 kN

  4. 32.81 kN
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C Correct answer
Explanation

For a three-hinged arch, the horizontal thrust H = sum(P*x*(L-x)) / (L*h). With loads 20 kN and 10 kN at specific positions, the maximum thrust is calculated by placing the loads to maximize the influence line for H. The calculated value is 31.25 kN.

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