Evaluation of advanced soil models for the cyclic soil-structure interaction of integral bridges

Integral bridges with longer spans experience an increased cyclic interaction with their granular backfills, particularly due to seasonal thermal fluctuations. To accurately model this interaction behaviour under cyclic loading, it is crucial to employ appropriate constitutive models and meticulously calibrate and test them. For this purpose, in this paper two advanced elastoplastic (DeltaSand, Sanisand-MS) and two hypoplastic (Hypo+IGS, Hypo+ISA) constitutive models with focus on small strain and cyclic behaviour are investigated. The soil models are calibrated based on a comprehensive laboratory programme of a representative highly compacted gravel backfill material for bridges. The calibration procedure is shown in detail and the model capabilities and limitations are discussed on the element test level. Additional triaxial tests with repeated un- and reloading reveal significant over- and undershooting effects for the majority of the investigated material models. Finally, cyclic finite element analyses on the soil-structure interaction of an integral bridge are conducted to compare the performance of the soil models. Qualitatively similar cyclic evolution of earth pressures are detected for the soil models at various bridge lengths and test settings. However, a substantially different cyclic settlement behaviour is observed. Additionally, the investigation highlights severe overshooting effects associated with the tested hypoplastic soil models. This phenomenon is studied in detail using a single integration point analysis. Supplementary studies reveal that the foot point deformation of the abutment significantly influences the lateral passive stress mobilisation and the amount of its increase with growing seasonal cycles.