The GATE Grind

GATE 2017 CE (CE1) – Question 39

Structural Analysis · Statically indeterminate structures: force and displacement methods · 2 marks · Multiple choice

The planar truss tower shown has statements P: externally determinate; Q: external static indeterminacy 1; R: external static indeterminacy 2; S: internally determinate; T: internal static indeterminacy 1; U: internal static indeterminacy 2. Which option is correct?

Diagram for GATE 2017 CE (CE1) question 39
  1. P false, Q true, R false, S false, T false, U true.
  2. P false, Q true, R false, S false, T true, U false.
  3. P false, Q false, R true, S false, T false, U true.
  4. P true, Q true, R false, S true, T false, U true.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (A) P false, Q true, R false, S false, T false, U true.

Explanation

The two pinned supports provide four reaction components, so external indeterminacy is $r-3=1$. Counting the six main joints and eleven members gives total static indeterminacy $m+r-2j=11+4-12=3$. The internal part is $3-1=2$. If the diagonal crossings are counted as joints, splitting the crossing members changes both counts but leaves this result unchanged. Therefore Q and U are true and the other statements false: A.

More Statically indeterminate structures: force and displacement methods questions

All Statically indeterminate structures: force and displacement methods questions →