Reliable collapse assessment of structural systems under earthquake loading requires analytical models that are able to capture component deterioration in strength and stiffness. For calibration and validation of these models, a large set of experimental data is needed. This paper discusses the development of a database of experimental data of steel components and the use of this database for quantification of important parameters that affect the cyclic moment-rotation relationship at plastic hinge regions in beams. On the basis of information deduced from the steel component database, empirical relationships for modeling of precapping plastic rotation, postcapping rotation, and cyclic deterioration for beams with reduced beam section (RBS) and other-than-RBS beams are proposed. Quantitative information is also provided for modeling of the effective yield strength, postyield strength ratio, residual strength, and ductile tearing of steel components subjected to cyclic loading. © 2011 American Society of Civil Engineers.