Nonlinear static and dynamic analysis is utilized by engineers to evaluate the seismic behavior of new and existing structures in the context of performance-based earthquake engineering. Numerous experiments on steel moment-resisting frames and their components have been conducted over the past two decades. The findings from these tests suggest that the current ASCE-41-13 nonlinear component models do not adequately simulate the steel MRF component behavior. As part of the ATC-114 project, new modeling recommendations are proposed for several structural steel components of new and existing MRFs including, steel beams, columns, the beam-to-column web panel zone, column bases and column splices. These recommendations are based on a consistent methodology that takes advantage of unique experimental data as well as insights from detailed finite element analyses. For each structural component of interest a set of equations is developed to predict their first-cycle envelope and monotonic backbone curves that can be directly used in nonlinear frame analysis. The proposed equations also include information related to the associated modeling uncertainty of each of the input model parameters. Through an array of illustrative examples, it is shown that the new recommendations reflect much more accurately the behavior of structural steel components from the onset of damage through the loss of their load carrying capacity.