This lecture covers the fundamental concepts of structural mechanics, focusing on moments and beams. It begins with a review of stress, defining it as the intensity of internal forces within materials. The instructor explains the relationship between force, area, and stress, emphasizing the importance of material resistance. The discussion progresses to the optimization of beam sections, highlighting how to minimize material use while ensuring structural integrity. Key concepts such as elongation, shrinkage, and deformation in bar networks are introduced, along with the influence of static height on structural performance. The lecture also delves into the definition of moments, illustrating how they are calculated based on force and eccentricity. Examples are provided to demonstrate the application of these principles in real-world structures, including the behavior of steel and concrete under various loads. The session concludes with a discussion on the significance of understanding these concepts for effective architectural design and engineering.