Numerical simulation of the structural behaviour of concrete tetrapods subject to imposed deformations and applied loads

Abstract

Tetrapods for coastal protection are frequently used in break waters for dissipation of wave energy. During their service, these plain concrete elements usually exhibit degradation signs with frequent premature rupture of one or more of their legs when located in highly aggressive environments subjected to extreme wave action. These ruptures tend to decrease the efficiency of breakwaters as a whole, thus diminishing their capacity to absorb wave energy. The present paper aims to contribute to a better understanding of the stress levels that occur in this kind of mass concrete elements, taking into account imposed deformations (associated with heat of hydration) and applied loads. A thermo-mechanical numerical simulation tool (3D), based on the finite element method, is used for the assessment of heat of hydration induced stresses. After an initial discussion of the temperature development inside the tetrapod, the corresponding residual stresses are presented and discussed, and conclusions are withdrawn with regard to the available capacity of concrete to withstand further applied loads. Finally, the subsequent behaviour of the tetrapod is assessed and compared to alternative solutions with internal reinforcement of the tetrapod legs, such as reinforced concrete (using stainless steel), steel fibre reinforced concrete and reinforced concrete with FRP’s.