SSS — Stochastic Seismic Spectra: Technical Lecture Notes and Methodological Report

SSS (Stochastic Seismic Spectra) is a research-oriented MATLAB toolbox for the time-domain random-vibration analysis of linear and equivalent-linearised Bouc–Wen single-degree-of-freedom systems under filtered (Kanai–Tajimi / Clough–Penzien), amplitude-modulated Gaussian seismic excitation. The state covariance is obtained from the evolutionary (differential) Lyapunov equation. The toolbox returns covariance histories of displacement, velocity and absolute acceleration, first-passage (reliability-based) peak estimates, and mean energy histories (kinetic, elastic, viscous, hysteretic, input). This record contains:- SSS-Spectra beta01 MATLAB source code (MIT License) – nominal linear and Bouc–Wen (n = 1, equivalent Gaussian linearisation) analysis, with example scripts.- SSS technical lecture notes and methodological report, version 2.3-beta (CC BY 4.0) – the formulation, and the planned adaptive integration (adaptive trapezoidal and TR-BDF2), mixed first-/second-order covariance sensitivity, uncertainty propagation and robust NSGA-II optimisation framework. Note: the manual (v2.3-beta) is ahead of the code. The adaptive integrators, sensitivities, uncertainty propagation and optimisation layer described in it are not included in the beta01 code, which implements the nominal analysis. Later versions of the code will be released as new versions of this record. Requirements: MATLAB R2018b or later (Control System Toolbox optional). Research software in beta: results should be independently verified before use in design. Authors: Giuseppe Carlo Marano, Laura Sardone, Alessandra Fiore, Rita Greco, Gaurav Datta, Arman Hajiha.