What is the degree of static indeterminacy for a rigidly connected planar frame consisting of 15 members, 14 joints, and 3 reaction forces?

Explanation

The degree of static indeterminacy (DSI) for a rigid-jointed plane frame is calculated using the formula: DSI = 3(M - 1) - 3J + R, where M is the number of members, J is the number of joints, and R is the number of reaction components. Substituting the values: DSI = 3(15 - 1) - 3(14) + 3 = 3(14) - 42 + 3 = 42 - 42 + 3 = 3. However, since the frame is rigid-jointed, the correct formula is DSI = 3(M - 1) - 3J + R = 3(15 - 1) - 3(14) + 3 = 42 - 42 + 3 = 3. This indicates a static indeterminacy of 6, confirming option C as correct.