This lecture covers seismic design in steel buildings, including capacity design, failure modes, and behaviour of concrete and steel. It also discusses the seismic behaviour of steel structures, common failure modes, and capacity design solutions. The instructor presents case studies of steel structures retrofitted for seismic resilience, detailing techniques for achieving large ductilities in moment resisting frames, and innovative solutions like 'Dogbone' beams and reinforcement of beam sections. The lecture concludes with a focus on buckling restrained braces as a solution to prevent buckling in steel frames under tension and compression loading.