The design and verification of structural systems for experimental prototype facilities represent one of the most demanding frontiers of modern structural engineering. Non-conventional structures, such as prototype facilities for physical experiments, large-scale detectors, large-scale vacuum and cryogenic chambers, low-frequency seismic isolation systems, large-scale infrastructure for industrial applications (e.g. [1-4])—often require highly customized solutions. Their design requires advanced engineering solutions and computational modelling to capture the interaction of complex geometries, hybrid materials, multi-material assemblies, extreme boundary conditions, and strict operational tolerances. This mini-symposium will focus on structural engineering challenges and computational mechanics methods applied to non-standard prototype facilities. Topics of interest include the development of advanced finite element models (1D/2D/3D and multiphysics), the implementation of material constitutive laws tailored to non-conventional components and the coupling between thermal, mechanical, and dynamic effects. Special attention will be given to the validation of numerical models against experimental tests, highlighting both laboratory-scale campaigns and full-scale measurements performed on working infrastructures. Another key aspect is the interaction between numerical simulations and design codes. While Eurocodes, AISC, or other standards provide a general framework, prototype facilities often operate outside traditional regulatory domains. This requires engineers to adapt and extend code-based approaches, integrating them with computational evidence and probabilistic safety evaluations. From an industrial perspective, the mini-symposium aims to bridge the gap between academic research and practical engineering applications. Industrial partners are increasingly involved in the fabrication and assembly of such facilities, where tolerances, connections, and construction sequences play a crucial role in the global structural response. Computational-experimental frameworks capable of anticipating these effects are therefore of paramount importance to reduce costs, improve safety, and accelerate installation schedules. Overall, the goal of this mini-symposium is to bring together researchers, engineers, and industry professionals working at the intersection of structural engineering, computational mechanics, and experimental validation.