oa Civil Engineering = Siviele Ingenieurswese - Research and model studies on range action in Table Bay Harbour, Cape Town : part II
Table Bay Harbour, Cape Town, is shown to be afflicted by two forms of surging, one of which is responsible for ranging of moored ships, the other for a pumping action of the basins and attendant navigational hazards. The construction and operation of a distorted model of Table Bay and harbour to reproduce the phenomena are descriptionbed. The model was proof tested in various ways and found reliable. Efforts to control the surging were directed chiefly to the Duncan Basin. Internal structures and re-positloning of the basin entrance failed to reduce the disturbances to harmless proportions. Suitable external structures of outer basin type, on the other hand, proved capable of inhibiting effects in the Duncan Basin. Success of the chain-system of basins is ascribed to its throttling effect on the long wave energy In the frequency range critical for moored ships. Measurements and theoretical considerations of ship motions and statistical analysis of rope breakages and damage all confirm that the critical period range for shipping is below 2 min and more particularly in the neighbourhood of 1 min.
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