An integrated analysis procedure for evaluating the nonlinear peak response of inter-story isolated structure employing an adaptive variable friction pendulum

Inter-story isolated structures with conventional friction pendulum isolators (FPIs) are not widely utilized because of their poor limiting ability and the absence of matching response spectrum analysis procedures. This study proposes an integrated analytical procedure (IAP) that effectively considers the structural characteristics and accurately evaluates the maximum response of a structure, eliminating the necessity of nonlinear response history analysis (NRHA). The procedure initially establishes a simple and practical mechanical model based on the characteristics of an adaptive variable friction pendulum isolator (AVFPI), in which the friction coefficient velocity dependency is obtained by fitting test data using a novel material, and the simplified theoretical mechanical model is evaluated via the same full-scale isolator test. In the context of stochastic vibration theory, the equivalent parameter of the isolation layer is determined by expressing it as the expected displacement amplitude. This expression was derived by employing the energy-balance approach in the state of maximum isolator displacement. Although the equivalent parameters depend on the mean square value of the peak displacement response, this study employs the peak coefficients of the statistical response on basis of the stochastic vibration theory without using the power spectrum as a solution technique. To achieve this, an iterative calculation procedure is designed by integrating the design response spectrum and the combination rule of the complex-mode-superposition complete square combination (CCQC). This process was used to construct the complete IAP framework. The accuracy of the approach was evaluated through a statistical analysis of a set of adaptive variable friction pendulum inter-story isolated structures (AVF-IISs), and its effectiveness was further confirmed through actual examples. The study revealed that the proposed mechanical model can effectively respond to the hysteretic behavior of the AVFPI. The developed IAP can achieve the desired range of prediction error for the displacement of an AVF-IIS, and the structural shear force prediction accuracy is acceptable.