Structural dynamics is a basic course that aims at providing fundamental knowledge concerning the dynamical response in the linear regime of typical civil engineering structures, in order to develop the skills necessary for the deployment and analysis of simple mechanical models to make sensible design choices as regards the response of a structure to dynamic inputs. This course is part of the master's degree program in "Civil Engineering for Protection from Natural Risks", which aims at training a civil engineer with high professional qualifications in the protection from hydrogeological and seismic hazards. The course aims at provide an in-depth knowledge 1) of the methods for setting up mathematical models that capture the essential aspects of the dynamic response of a structure; 2) basic concepts for the study of linear systems with a finite number of degrees of freedom; 3) of the essential concepts for the study of the dynamic response of continuous systems. At the end of the course students will be able to: 1) know how to use the methods of theoretical mechanics and mechanics of structures to schematize a real structure using a model that captures the essential aspects of the dynamic response; 2) evaluate the dynamic response of systems with a finite number of degrees of freedom; 3) evaluate the dynamic response of continuous systems.