Using FBGS to estimate the horizontal response of a monopile in a geotechnical centrifuge

A circular aluminium tube 50 mm in diameter was instrumented with two optical fibres, each of which consists of 13 fibre Bragg grating sensors (FBGS). The performance of the FBGS was evaluated by applying a series of increasing transversal loads at 1g level and comparing the strains measured by FBGS with those calculated from the Euler−Bernoulli beam theory. A centrifuge test was then conducted at 100g to estimate the transversal response of the calibrated model pile that had been jacked 450 mm into saturated sand and horizontally loaded at 500 mm above the ground. The profiles of the normal strain, bending moment, soil reaction and pile deflection were measured or determined, enabling the plotting of the soil reaction-pile deflection (P-y) curves. The results confirmed the reliability of FBGS at 100g by yielding satisfactory measurements on bending moments and coherent measurements on shear force at the ground level.