MEASURED AND PREDICTED WAVE PLUS CURRENT LOADING ON A LABORATORY-SCALE, SPACE FRAME STRUCTURE

A wave tank model test program was carried out, using a 1:47 scale model of a space frame structure, to evaluate the use of the Morison force equation for calculating: a) total wave plus current (towing) loads on structures and b) vertical loads on conductor guide frames. Prototype-scale wave heights ranged from 0-70ft and current speeds ranged from 0-5kt. Predicted hydrodynamic loads, based on laboratory-scale wave force coefficients, were compared to the measured loads. Results show that total wave plus current loads are predictable if proper account is taken of model-scale drag and inertia coefficients. However, the drag coefficient needed to explain the loads in the wave plus current tests is considerably smaller than expected from laboratory data on single cylinders. This may be a scale effect or it may be due to shielding. The incremental total vertical force due to the conductor guide frames is predicted reasonably well if the frames are assumed to act hydrodynamically like flat plates.