As part of our ongoing work on structural safety under extreme actions, we carried out an advanced assessment of the reinforced-concrete walls protecting hydrogen storage vessels at an industrial facility.

The Eurocode provisions for accidental gas explosions (developed for methane and limited-volume rooms) are not directly applicable to open-top hydrogen compartments, where reaction mechanisms and available gas quantities differ significantly. For this reason, we adopted a multi-level numerical approach combining:

• Linear elastic FE analysis to obtain first-order capacity estimates.
• Nonlinear static simulations with layered-shell models to capture cracking, hinge formation, and redistribution of internal forces.
• Dynamic considerations to evaluate the influence of inertia, strain-rate effects, and the non-simultaneity of pressure peaks on structural response.

The study revealed that the critical failure mode is overturning of the long walls, and that nonlinear behaviour significantly increases the predicted blast resistance compared with linear methods.

We also explored mitigation strategies using steel portal frames, which substantially enhance the maximum pressure the system can resist.

This work demonstrates how advanced numerical modelling can support safe and economical design in scenarios where code-based simplified methods are not sufficient.