Multiple choice

A beam PQRS is 18 m long and is simply supported at points Q and R 10 m. Overhangs PQ and RS are 3 m and 10 m part. Overhangs PQ and RS are 3 m and 5 m respectively. A train of two point loads of 150 kN and 100 kN, 5 m apart, crosses this beam from left to right with 100 kM load leading.

The maximum sagging moment under the 150 kN load anywhere is

  1. 500 kNm

  2. 45 kNm

  3. 400 kNm

  4. 375 kNm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The maximum sagging moment under a point load occurs when the load is placed such that the average load on either side of the section is equal to the load at the section. By calculating the influence line for the moment at the critical section, the maximum value is found to be 400 kNm.

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