Two-stage analysis has been performed by structural engineers since its introduction to the code in the 1988 Uniform Building Code. This analysis procedure simplifies the analysis and design of a flexible structure supported by a rigid structure while allowing proper base shear scaling and use of R-factors of the two structures. However, despite its original intent, two-stage analysis can prove to be difficult to implement in complicated structures. Through our experience with the design of two new hospitals and evaluation of one existing hospital, we highlight to practicing seismic engineers and code developers some challenges and recommendations regarding (a) code interpretation and intent of the two-stage analysis provisions, (b) application, idealization and modeling of boundary conditions and soil springs, and (c) use and limitations of analysis models and software.
展开▼
