The document discusses plastic analysis of slabs. It begins with defining a slab as a structural element contained in a plane where the load direction is perpendicular to the plane. It then mentions elastic analysis of grids and frames before introducing plastic analysis of structures like beams and frames. A key aspect of plastic analysis of slabs discussed is yield lines, which are lines of plastic rupture or rotation lines. The document also references a slab for assignment 6 and plastic analysis of slabs.