The Digital-Twin-as-a-Service is a digital platform designed to ease the building, deploying, using, and sharing of digital twins in a collaborative environment. The platform is a multi-user environment with dedicated virtual workspaces for each user. In addition, the platform provides common services like communication to all users. In this study, the platform is used to create a vibration-based monitoring workflow, where the data from the vibration sensors installed on the physical structures flows to the function blocks, which implement different structural analysis methods. The function blocks run in the private workspace of a user on a remote server. The workflow consists of several branches: (i) the vibration data is used to infer modal parameters through system identification; (ii) the obtained modal parameters are used to update the finite element model of the structure; (iii) the measured vibrations and the mode shapes of the updated model are used to estimate the full-field displacement and strain fields by means of modal expansion-based virtual sensing.