Fall Arrest Governs the Design of Lightweight Working Platforms for Steep Slopes: Finite Element Analysis and Code-Based Assessment of a Modular Aluminium System

Stone pitching and other finishing works on steep infrastructure slopes (45–60°) are still commonly executed by workers standing on the inclined surface. This paper assesses a modular system of aluminium stringers resting on the slope and horizontal platforms connected by pins and hooks, derived from a Spanish utility model. The original shell finite element analysis (FEA) was re-examined with an independent shell FEA built from the original geometry and verified against benchmarks and closed-form solutions, complemented with a mesh-sensitivity study, a sub-model of the pin holes, frictional contact with the slope and code-based checks to EN 12811-1 and Eurocodes 3 and 9. Deflections under imposed load agreed within 4% between models and changed by less than 1% with mesh refinement, whereas peak stresses at the idealised connections increased by up to 3.5 times; connections were therefore verified with code resistance models. For two workers per platform, the selected configuration (60 × 40 × 3 mm platform tubes and 250 × 40 × 3 mm stringers in EN AW-6063 T6) reached a maximum utilisation of 0.87, and the end-of-span load case did not govern. A single 6 kN arrest force at an integrated anchor point exceeded the elastic limit of the platform by 1.4–2.1 times and reached 86–115% of its plastic collapse load, leaving no margin for dynamic amplification or for the 12 kN static strength of EN 795. Fall arrest therefore governs any integrated anchorage, which should be replaced by an independent anchor device; driven-bar ground anchors were also found to be insufficient in granular soils.