SAFETY OF WHARVES.

New Zealand Herald, Volume LXVI, Issue 20303, 10 July 1929, Page 10

SAFETY OF WHARVES.

THE EARTHQUAKE DANGER.

AN AUCKLAND PROBLEM.

PROPOSALS BY ENGINEER

STRENGTHENING TO COST £SOOO,

Proposals for strengthening Prince's, Queen's and King's Wharves against earthquakes at a cost of about £SOOO, arc to be considered by the Auckland Harbour Board.

The matter was brought up at (he board's meeting yesterday by the engineer, Mr. D. Holderncss, who pointed out in a report that the risk ol damage was not negligible, and that those wharves built up to 1925 had no structural provision against earthquakes, although the later ones were strengthened against lateral stresses.

The report was as follows: — "Tho 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 sinco 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.

"While the shore end of a wharf is reasonably bracd against (he land* (lie 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 beard to consider whether expenditure in this direction would not be a wise in-

sura nee. "An expenditure of approximately £2OOO on Prince's Wharf, £ISOO on Queen's Wharf and, say, £1250 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 pro-

gramme." The report was referred to the board-in-conimittee, several members remarking that the matter "was most important and should be dealt with without delay.