Meriam's Theorem is a principle in structural analysis that helps determine the internal forces and reactions in a structure. It states that for a system in equilibrium, the sum of the moments about any point must equal zero. This allows engineers to analyze complex structures by breaking them down into simpler components. The theorem is particularly useful in the study of beams and trusses, where it aids in calculating forces acting on different members. By applying Meriam's Theorem, engineers can ensure that structures are safe and stable under various loads, making it a fundamental concept in civil and mechanical engineering.