Centrifuge modelling of single- and two-span bridges with rocking foundations

This paper presents a comparison of the seismic response of single-span bridge rocking foundation (SSBRF) and two-span bridge rocking foundation (TSBRF) bridge models incorporating rocking shallow foundations supported on dry soil. Physical models representing one- and two-span sections of a prototype bridge were tested in a geotechnical centrifuge and subjected to scaled historic earthquake motions. Foundation settlements, rotations, and deck drifts were measured to evaluate differences between the two configurations under dry conditions. Results indicate that both systems exhibited settlement-dominated rocking behaviour, with residual settlements and rotations remaining small. On average, the TSBRF developed ≈38% larger maximum foundation rotations and 189% larger residual rotations at the leading foundation than the SSBRF. Deck drifts were minor and well below allowable limits, and no toppling occurred. Relatively slight differences were observed between the single- and two-span systems, suggesting that bent location, number of bents, and span configuration had limited influence on responses in dry soil conditions. Slightly larger settlements in the single-span system during higher-intensity motions may reflect the stabilising effect of additional bents in the two-span configuration. These observations provide insight into the soil behaviour of bridge systems with rocking shallow foundations in dry conditions.