4 CONCLUSIONS
The design of structures submitted to cyclic lateral actions from wind or waves is a complex problem which requires consideration of a lot of factors. Such structures are often founded on piles. Under a certain series of loading-unloading cycles an accumulation of displacements is taking place on the pile head. Ignoring this accumulation could lead to unconservative design and, sometimes, to disastrous consequences for the future structures. The objective of the present paper is to develop a numerical model for simulating this cumulative behaviour, in order to be able later to model different types of situations. The numerical model was developed using the Finite Elements Method and has been calibrated based on small-scale centrifuge tests results.
The experimental test has been carried out at IFSTTAR Nantes, France by Rosquoët (2004) on a small-scale aluminium pile model installed in medium Fontainebleau sand and submitted to 15 loading – unloading cycles.
The numerical model was performed in the CESAR-LCPC finite elements software (version 6.0, ITECH 2014). The main challenge of the model consisted in implementing a hardening kinematic part to the classical Drucker-Prager constitutive law, in order to obtain the displacement accumulation during the cycles.
The obtained results showed a very good agreement between the experimental displacements at pile head and the numerical ones (229 mm numerical displacement at the end of the 15th cycle and 228 mm experimental one – prototype values), for the “perfect sliding”-type interface. On the other hand, the numerical model perfectly simulates the decreasing of displacement accumulation with the cycles.
