A collaborative research project is underway at the University of Minnesota Multi-Axial Subassemblage Testing (MAST) Laboratory regarding the behavior of structural wall systems. The investigation included tests and numerical simulations of three rectangular reinforced concrete wall systems to investigate the effect of continuous, spliced, and mechanically connected longitudinal reinforcement at the wall-foundation interface. It was anticipated that the different reinforcement details would have an effect on the plastic hinge length, local strain demands, and consequent flexural (deformation) response including the damage state of the wall systems. The walls were instrumented to investigate the overall behavior and to isolate the individual deformation components attributed to flexure and shear. Understanding the sources of deformation and correlation of the results with models that can be used to predict the behavior is important for development of performance-based seismic design procedures. The project was funded by the National Science Foundation (NSF) grants CMS0324504 and CMS0324559.