Stacked bi-material strips to mimic tyre loads on FRP decks

This experimental and numerical paper presents a modified version of the conventional steel plate-rubber pad device to replicate tyre-load contact pressure distributions (CPDs) on fibre reinforced polymer (FRP) bridge decks, as required by CEN/TS 19101. The steel plate remains, but underneath, the single continuous rubber-only pad of the conventional approach is replaced by strips that in plan match the tyre tread contact patches, each strip comprising stacked cork and rubber layers. The plate is indeterminate owing to these multiple strip supports underneath. Hence, the load applied to the plate is distributed between and along strips according to the strips’ stiffness profiles, which in turn are manipulated by tuning the thicknesses and stacking sequences of the cork/rubber layers. It is shown experimentally that both n and M CPDs from lorry and van tyres are successfully replicated via this approach. Test-verified finite element analysis reveals that suitably designed bi-material strips correctly mimic local tyre load effects across the deck, but that the conventional continuous mono-material pad either significantly over-emphasises or conversely runs the risk of significantly under-emphasising these local effects in some parts of the deck, and so could either trigger damage sites within the deck that are non-existent under tyre loading or can conceal damage sites that are induced by this tyre loading. Bi-material strips beneficially retain the simplicity of conventional plate-pad systems, while closely mimicking tyre CPDs. • Tests on application of narrow van tyre concentrated loads to cellular FRP decks. • Sensors used to log action (contact pressures) and deck’s local response (strains). • Devised bi-material cork-rubber strips under steel plate to mimic tyre tread loads. • Both n-shaped and M-shaped contact pressure distributions are reproduced by strips. • Mono-material pads can strongly exceed tyre effects to cause spurious damage sites