Robust-to-Change Stiffness Allocation for Tall Structures

Abstract

A computational procedure for robust-to-modeling and robust-to-change design of structural systems is proposed with application to planar rigid frames. A structure is considered robust when it is least sensitive to changes that alter its system coefficients (stiffness matrix for static loading). The upper limits of change from perturbations in the stiffness matrix are available from linear algebra; however, what is not clear is an ideal pattern of material allocation throughout the structure, or a preferred preliminary model from a set of viable models, such that it results in a final design that has low error bounds while satisfying the limit states of performance and safety. Because gradient-based optimization is not feasible, the authors rely on statistical simulation techniques to study the variation of error upper bounds in structural response when the system is subjected to changes in its components (elasticity, cross-sectional dimensions, member lengths). Application of the methodology to lateral design of a set of multistory rigid frames shows that initial models with uniform material distribution over their height produce more tolerant designs. Along the way, the authors analytically present the necessary condition for making multiobjective design (also known as performance-based design) of multistory frames with a single objective. The procedures have the potential of saving time and resources during the lengthy design projects and creating structures that are more tolerant to change, hence improving their resiliency and lifespan.