B efore large panel concrete wall structures can be used with confidence in seismic zones, a clear understanding of their behavior under potentially severe earthquake loading is required. Such understanding can be provided by a combination of experimental investigation in the laboratory, analytical studies, and observation of performance of structures that have been constructed in various parts of the world. P'intel' reported that precast panel buildings performed well during the 1977 Romanian earthquake. However, large panel precast wall systems have not yet found general acceptance for resisting earthquake forces in North America. At a recent PCI sponsored workshop on the Effective Use of Precast Concrete for Seismic Resistance,' the need for research in this area was emphasized. Several experimental investigations on behavior of large panel wall systems have been reported in recent years. Oliva and Shahrooz 3 conducted shaking table tests of one-third size scale models of three story systems consisting of solid walls, walls with door openings, and wall panels with adjoining and flange walls. Shear slip motion was constrained by shear keys. The result was that limited shear slip took place and behavior was dominated by rocking. Stress concentrations were induced at wall ends, leading to concrete crushing as a result of rocking motion. Velkov et al. 4 tested specimens similar