Abstract: Cast-In-Drilled-Hole (CIDH) reinforced concrete shafts/columns are common support structures for highway bridges in urban areas. The construction simplicity of these foundation structures provides great economical benefits; however, their performance under strong earthquake loading is of interest, to improve both safety and economy. The objective of the study is to perform analytical studies on the behavior CIDH shaft/columns, and to develop, calibrate and validate numerical models for design and analysis. The analytical studies comprise the development of a new and simple macroelement model, which is amenable for routine analysis by practicing engineers, and the construction of a set of three-dimensional finite element models to be used for more detailed investigations. The developed macroelement model considers nearly all of the major phenomena (with the exception of radiation damping) of soil-structure interaction in a modular, and concise mathematical format. The calibration and validation of the analytical/numerical models are achieved through the use of experimental data obtained from a full-scale test carried out at UCLA. Additionally, a macroelement model that is capable of considering effects of simultaneous axial and lateral loads on deep foundations. Due to lack of reliable experimental data, this model is only calibrated and validated using data from three-dimensional finite element simulations.