6) Castigliano's first theorem is applicable: For statically determinate structures only. 2. When the system behaves beyond the elastic limit. 3.Only when principle of superposition is valid. 7) A single moving load of 8kN along a girder of 15m span. The Influa absolute maximum bending moment will be: line 1.8 kN.m 2.15 kN.m 3.30 kN.m 460 kN.m 8) The flexibility matrix is a 1.Square non-symmetrical matrix. 2.Square symmetrical matrix. 3.Square symmetrical matrix with zero diagonal elements. 9) For stable structures, the diagonal elements of the flexibility & stiffness matrices are: i. For stiffness matrix must be positive. ii. For stiffness matrix must be negative. iii. For flexibility matrix must be positive. iv. For flexibility matrix must be negative.