Correct Answer - Option 4 : Force method
Concept-
Flexibility Matrix Method:
1. This method is also known as the force method or compatibility method.
2. It is suitable if kinematic indeterminacy (Dk) > static indeterminacy (Ds) for the structure.
Flexibility is defined as Displacement caused due to unit Force.
δ12 → Displacement at 2 due to Force at 1
Important points of flexibility matrix:
(i) Order of matrix is the number of coordinates chooses for the solution of the problem.
(ii) Elements of flexibility matrix are displacements.
(iii) Flexibility matrix will always be a square matrix.
(iv) Elements along the diagonal will always be non-zero and positive. Other elements can be zero or negative.
(v) Matrix will always be a symmetric matrix about its main diagonal. This follows maxwell reciprocal theorem fij = fji
(vi) Flexibility matrix can be calculated only for stable structure in which there is no rigid body displacement.
(vii) In the flexibility method of analysis, we have to determine the degree of statical indeterminacy, and also we have to remove the redundant to obtain primary determinate stable structure initially.
(viii) Flexibility method is also not applicable to an unstable structures.
