Nonlinear Structures & Systems, Volume 1: Proceedings of the 38th IMAC, A Conference and Exposition on Structural Dynamics, 2020, the first volume of eight from the Conference brings together contributions to this important area of research and engineering.  The collection presents early findings and case studies on fundamental and applied aspects of Nonlinear Dynamics, including papers on:Nonlinear Reduced-order ModelingJointed Structures: Identification, Mechanics, DynamicsExperimental Nonlinear DynamicsNonlinear Model & Modal InteractionsNonlinear DampingNonlinear Modeling & SimulationNonlinearity & System Identification