This lecture covers topics related to shear and bearing stresses in structural mechanics, including plasticity, creep, shear stress and strain, bearing stress on bolts, Hooke's Law in shear, and examples of bridge bearing pads under shear. The instructor explains the concepts of shear strain, equality of shear stresses on perpendicular planes, and shear stress sign conventions. The lecture also discusses the importance of allowable stresses and loads in engineering design, emphasizing factors of safety and the relationship between actual strength and required strength.