Seismic Displacement Demands for Hybrid Precast Concrete Shear Walls

This paper presents an analytical investigation on the peak lateral displacement demands of “hybrid” precast concrete panelized shear wall structures under seismic loading. The hybrid wall structure investigated uses a combination of mild [i.e., Grade 400 (U.S. Grade 60)] steel bars and highstrength unbonded post-tensioning (PT) strands for lateral resistance across horizontal joints. The analytical work follows from a previous experimental validation of the hybrid wall system for ACI 318 (2011) adoption as “special” reinforced concrete shear walls based on the testing of six 40%-scale precast test specimens (four solid and two perforated walls) under reversed-cyclic lateral loading (Smith et al. 2012). The broad goal of the analytical program was to accurately reproduce and predict the hysteretic behavior of the hybrid system. Upon successful validation of the analytical models based on the measured behaviors of the test specimens, nonlinear dynamic time-history analyses of a full-scale prototype structure were conducted under an exhaustive ensemble of selected ground motion records. The dynamic analysis results provide a critical link between the prescribed lateral displacements that were used in the design and validation testing of the wall specimens per ACI ITG-5.1 (2007) and the expected seismic demands from earthquake loading. Ultimately, these results further support the successful code approval of hybrid precast concrete shear walls for moderate and high seismic regions of the United States.