DANGER FROM ’QUAKES

Sun (Auckland), Volume III, Issue 711, 10 July 1929, Page 6

DANGER FROM ’QUAKES

STRENGTHENING WHARVES PROPOSAL BY ENGINEER Stating that the risk of damage to the Prince’s, Queen's, and King’* Wharves by earthquake was not negligible, the Harbour Board’s engineer, Mr. D. Holderness, submitted proposals to the board yesterday afternoon for strengthening the structures. f'PHE possible effect of ’quakes, and suitable methods for making the wharves more secure, were outlined by Mr. Holderness in a report. He estimates the cost at £5,000. The report Is as follows: ’’The earthquake experienced throughout a considerable part of .New Zealand on June 17 last was distinctly felt In this city, and on the board’s wharves. Special provision for lateral stresses has been made in all the board’s wharves constructed since 1925, particularly Onehunga Wharf, Western Wharf, and the new wharves at Devonport. Prior to that date no special provision had been made in the main wharves to counteract the effect of earth waves, and so long as these do not materially exceed those so far experienced in Auckland no apprehension need be felt regarding their effect on the board’s structures. There can be no doubt, however, that serious earthquakes might cause considerable damage. “Whereas a reinforced concrete wharf structure appears massive, and particularly stable, it must be borne in mind that its weight is carried on very long and comparatively slender piles, and that it is not so well braced as a building on shore, where the spaces between columns are filled in by solid panels. ADDITIONAL SECURITY “While the shore end of a wharf is reasonably braced against the land, the outer end is much more flexible, and prolonged earthquakes, the periodicity of which corresponds with the natural period of vibration of the wharf, might be expected to set 'Up dangerous oscillations. "It is obviously impossible to provide positive safeguards against the type of earthquake which permanently alters the level of, or disintegrates, the earth’s crust, but in the case of normal earthquakes a considerable amount of additional security could be provided by a system of raker piling in the outer ends of the wharves, and it would be well for the board to consider whether expenditure in this direction would not be a wise insurance. o expenditure of approximately £2,000 on Prince’s Wharf, £1,500 on Queen's Wharf, and, say, £1,250 on King’s Wharf, would very considerably assist these structures in resisting the oscillations caused by earthquakes, and I would recommend the board to authorise the work for inclusion in next year’s programme." The board-in-committee will give immediate consideration to the report. Several members remarked that the subject was most important, and that it should be dealt with at once