Application of EPS Geofoam below Soil-Steel Composite Bridge Subjected to Seismic Excitations

Soil-steel composite structures are commonly considered competitive alternatives to conventional small road and railway bridges. The structure is made from corrugated steel plates and comes in various profiles and shapes, up to 32 m at most. These structures are also found in seismic areas. Despite this, knowledge of their seismic behavior is limited. The paper analyzes the seismic behavior of an existing soil-steel composite bridge in Poland, where full-scale tests have been conducted. The analyzed bridge has a total height of 6.05 m and a span length of 17.67 m and was built with 140x380 mm corrugation and 7-mm thick steel plates. Numerical analyses are performed on the bridge using the finite element (FE) program DIANA FEA with seismic records from the 1940 El Centro earthquake as a reference. Expanded polystyrene (EPS) geofoam is applied under the structure and studied in the numerical models to reduce the impact of seismic waves on the bridge. The first numerical model was created without geofoam for calibration purposes, and the latter five with EPS given different stiffness properties (densities and Young's modulus). The results suggest that EPS has advantageous features (especially with low stiffness) in reducing the maximum deformations and stresses on the steel shell by absorbing (damping) the energy of the seismic waves and rearranging the stresses away from the structure and to the soil. This trend was particularly evident when comparing the five models built with EPS to the model without EPS, where stresses in the structure were significantly higher, demonstrating the material's ability to rearrange the stresses away from the structure. Soil-steel composite bridges are commonly considered competitive alternatives to conventional small road and railway bridges. The shell structure is made from corrugated steel plates backfilled by granular soil and comes in various profiles and shapes, up to a maximum of 32 m. These structures are also found in seismic areas. Despite this, knowledge of their seismic behavior is limited. This paper analyzes the seismic behavior of an existing soil-steel composite bridge. The EPS geofoams were applied under the structure and studied in the numerical models to reduce the impact of seismic waves on the bridge. The results suggest that EPS has advantageous features in reducing the maximum deformations and stresses on the steel shell by absorbing the energy of the seismic waves and rearranging the stresses away from the structure and the soil. The obtained results may contribute to the dissemination of these bridge structures in seismic areas.