System identification of a volumetric steel modular frame using experimental and numerical vibration analysis

This paper presents the findings of an experimental and numerical study on the system identification of modular steel frames in a laboratory environment. The project is a part of a broad study about the structural response of modular steel buildings. For this purpose, an experimental program is conducted on a full-scale volumetric prefabricated steel module, which is designed based on Australian standards. The module is fixed on a strong floor, instrumented with sensitive accelerometers, and its ambient and free vibration responses are captured and recorded. The output-only algorithms of operational modal analysis procedure, that is, direct fast Fourier transform, enhanced frequency domain decomposition, and stochastic subspace identification, are employed for extracting the main dynamic properties of the module, including natural frequencies, mode shapes, and modal damping ratios. Then the numerical finite-element models of the module are generated in micro and macro levels with continuum solid and beam elements, respectively. The numerical models are verified with the results of the experimental program and the discrepancies are discussed. The findings of this study are be used as a basis for research on the fundamental behavior of steel module assemblies and their interaction for the design of multistory modular buildings.