Explore the principles of structural dynamics and earthquake engineering, examining the dynamic response of structures to seismic forces and the methods for evaluating their seismic performance. Discuss the factors influencing structural response to earthquakes, including material properties, structural configuration, and ground motion characteristics, and their implications for design criteria and seismic retrofitting strategies. Evaluate the effectiveness of different seismic design approaches in ensuring the safety and resilience of civil infrastructure, considering factors such as cost$,$ complexity, and risk mitigation.