Thermally-induced ratcheting of a thermo-active reinforced concrete pile in sand under sustained lateral load

Thermally-induced ratcheting of a thermo-active pile is the accumulation of net and irreversible pile head displacement upon heating-cooling cycles. Although this kind of phenomenon has been observed in vertically-loaded piles in sand, it is unknown whether this exists in laterally-loaded cases, and also what underlying mechanisms occur under the thermomechanical flexural soil-pile interaction. This study presents a series of centrifuge tests and finite-element simulations of the thermomechanical behaviour of a laterally-loaded thermo-active pile in sand. A new model reinforced concrete (RC) was used in the centrifuge tests to realistically mimic the thermal and mechanical properties of a prototype RC pile. Ratcheting was evident in laterally-loaded piles and its extent was more significant when the working horizontal load is higher. The ratcheting phenomenon was attributed to the accumulation of soil plastic strain due to the cyclic mechanical loading induced by pile thermal horizontal expansion and contraction, soil dilation upon soil-pile interface shearing, and creep. The additional bending moment induced by the thermal action did not induce yielding within the pile. A subsequent numerical sensitivity study suggested that ignoring the softening behaviour of the sand would lead to underestimation of the magnitude of the accumulative thermally-induced pile head lateral displacement.