Development of a concrete prototype truss structure for floating wave energy converters: Digital design, manufacture and flexural performance

Wave energy will play a vital role in creating a balanced onshore and offshore renewable energy mix. This paper reports on the design, numerical analysis, manufacture and testing of a prototype precast concrete Vierendeel truss structure which could form the inner structure 3.5 m in length and 0.93 m in diameter. The basis for design meant that only two shapes of truss members were used to aid faster production. An anchoring system consisting of steel dowel connectors and grouted epoxy resin was used to increase rigidity and integrity. Precast concrete and steel wires for prestressing were used as the trial for addressing design concept. The prototype was tested being subjected to monotonic bending load physically and numerically. It was observed the truss mainly exhibited an elastoplastic behaviour before the deformation of 10 mm at the monitored middle ring. The tolerance of precast concrete and assembly were identified as causing the less stiff response of the truss. Mechanism of the epoxy and epoxy-bonded anchors was investigated using custom testing methods. The simulated stress distribution characteristics revealed by numerical modelling implicated that the connecting between segments was exposed to higher tensile strength causing potential concrete cracking. The presence of the epoxy-bonded anchoring and its influence to the integrity of the truss was identified as the source dominating the failure of the truss.