University of British Columbia, Kelowna
Building codes and standards in many parts of the world recognize the first significant yielding point as an ultimate limit state for the wind design of tall buildings. The main argument used in favor of linear-elastic analysis approach is its presumed ability to avoid asymmetric yielding and the subsequent permanent set (accumulated damage). However, this design philosophy ignores the ductile capacity of materials and structural systems, resulting in uneconomical and brittle buildings. Thus, classical linear-elastic design arguments should be re-examined with consideration of performance-based wind engineering (PBWE) approaches, innovative technologies, and materials.
In this study, using dynamic time history analysis, we initially examined the cumulative damage demands of single-mass oscillators modeled with nonlinear-inelastic (bilinear) and nonlinear-elastic (self-centering) hysteretic models subjected to artificially generated wind speed times series. Analysis results of the bilinear systems show that damage accumulation could trigger the failure of structural systems. However, self-centering systems controlled permanent set by a complete re-centering at the end of excitation. Hence, we proposed a new performance objective in the nonlinear range.
For demonstration, we incorporated the new performance objective in the PBWE framework and applied it to design a 558-meter-tall tower equipped with unbonded post‐tensioned tendons. Aerodynamic wind tunnel tests are conducted to obtain wind load time histories over the height of the tower. Nonlinear dynamic structural analysis is carried out to determine the response history of the tower. The results prove that, with the use of self-centering systems, PBWE approaches can be effectively used to design economic and ductile structures.