The seismic response of cable-stayed bridges is characterised by complicated interactions between the deck and the towers. These are influenced by the possible damage in the structure, and also by design choices or constraints such as the tower shape, the span, the cable arrangements, the support conditions and the type of foundation soil. The aim of this work is to assess the influence of these effects on the seismic behaviour of a large number of cable-stayed bridge finite element models. The results of the nonlinear dynamic analyses show the importance of the tower geometry. This is especially significant in short-span bridges with abrupt changes in the inclination of the lateral tower legs, which can lead to large levels of damage in the form of concrete cracking, reinforcement yielding and overall energy dissipation. Finally, design recommendations are proposed to improve the seismic response of the towers.

The elasticity law is a great challenge in soils, due to the well-known non-linear, anisotropic, pressure-dependent soil response even at negligibly small strains. A new hyper-elastic formulation is proposed, based on a polynomial expression (including a fabric tensor defining the elastic anisotropy) with two branches, one for the negligibly small stresses, ensuring good convergence properties at low confining pressure, and one for the soil response at intermediate strains, corresponding to stress states inside a single large-sized, yield surface defining the occurrence of large irreversible strain. Typical numerical simulations are discussed for isotropic and oedometric compression and swelling tests, and for undrained triaxial compression tests. The results are compared with those obtained with similar hyper-elastic models proposed in the literature. A comparison with experimental oedometric and drained and undrained triaxial tests on undisturbed samples of London clay is provided, revealing that the proposed model has great flexibility in selecting both the shear stiffness and the evolution of elastic anisotropy, which can be chosen independently, thus providing a general applicability. For instance, the great flexibility of the proposed hyper-elastic formulation can be exploited to model the non-linear swelling curves typically observed in oedometric swelling tests of structured clays or active clays.