’QUAKE PRECAUTIONS

Gisborne Times, Volume LXXII, Issue 11453, 2 March 1931, Page 3

’QUAKE PRECAUTIONS

PREVENTION -OF T) AM AGE

AN EXPERT’S REPORT

b Mr. J R. Baird, A.M.N.Z., Roc. C.E.', presented a report to the Association of . Engineers’ Conference at Auckland last week on the . question of the prevention of. damage by earthquakes, The following is a brief Nummary

Everyone . should, of course, realise that by living in New' Zealand he takes,.a certain definite risk. Our country lies on that, part of ."the world where some' of .the tremendous energystored up. as' the result pt continual shrinkage of the earth, will he released from time tfl- time.- Energy rele.ased-.in this-manner .produces the most destructive of,the. forces of. nature and to build our homes And cities with no regard to such forces is nothing short, of an elaborate preparation for suicide. We cannot yet tell ,at what: time nor in what ..place's future shakes will occur A-nor. would it bh of great advantage were, this power given to us. This does not imply that we should abandon our country hut simply that we should tako the sage step of designing our cities to salely withstand such occurrences., , . (1) The loss of life was due almost entirely to the c.ollapse of, buildings. Tf thovsanio number of people .find been present, but tents instead of buildings had bee,n the ‘.‘fnsljion.,’’, it is safe ip.say that, very little personal injury would htmv resulted. Hence the earthquake did not cause the s were caused by the conditions . the people had created over, a; period of, years. The, prevention' of future deaths lies in the compulsory adoption of buddings Wiueh will not. collapse. (2) The loss of buildings was due to entirely inadequate design as already stated. (3) The loss of stocks, etc., was also due to a. great extent, to Hie collapse of the buildings which event in many cases caused lire which added to.the loss.

' (i) The loss of service was also due chiefly.to the collapse of the oily buildings and the’ structures directly connected with the “‘services. (n) .Loss of communication was again due chiefly to the collapse of buildings, bridges, and other. structures. (6) Loss of trade will come directly as the loss ot the place of business. From the foregoing it is clear that probably DO per cent, of all losses wore due to structural deficiencies.

(1.) The first fundamental condition is site. Proximity to a known fault is generally regarded as the most dangerous position hut it would seem wise for us to adopt a uniform standard. Sites'at the foot of or on ’be sides of steep hills or on the tops of cliffs are insecure. Rock forms'the best foundation material while swamp and reclaimed land is the worst.

(2) The second fundamental consideration is. shape." The more closeiy a building approximates a square m plan the safer'it will bo*. L and 1J types commonly used for schools and hospitals are particularly bad but a closed rectangle, provided the hollow i's not too large, is satisfactory. In elevation a building should also be as symmetrical as possible and it is desirable that towers should be omitted. If used they should he placed on the axis of the building ■nid should he very carefully designed

(31 Foundations of a building -diould be carried down to a uniform depth..over the entire site and should on 'no account, rest on dissimilar materials, e.g., partly on clay and partly on Tilled ground

(4) Individual column footings should not be allowed hub. all foundations of n building should he connected in at .least two directions at: right angles. Ope large renforeed slab or “raft” under the entire building is the ideal foundation. Soil pressures should be kept as low as ■possible, it will be seen laier that pressures under the outer columns or walls, will during an earthquake •oitsiderably exceed normal, l'ounletions, whatever form they take, should therefore bo able to project beyond the face of the outer- walls on .all sides (see 6) as eccentric footings should be avoided. (5) The ratio of height to thq least width of base should be. limited to II to I with a maximum of 100 feet, fo'r rock, 1 to 1 with a maximum ot 66 feet for firm soil, i to 1 with a maximum, of 33 feet for swamp and reclaimed land or piles. (6) City buildings in one block should be made structurally one building (although outwardly they :x>uld appear as a number of separate buildings) or else a clear space • of. 3 feet should be left between the structural frames or walls of adjacent buildings. The ground .floor and shop windows could, however, be allowed to utilise the whole of the frontage provided they are designed to ‘'crumple” without transferring my serious stress from one frame to the next. (7) Every part or component of a building should be so tied together that none, can fall away when under the influence of the maximum acceleration expected (See 8). For this reason brick, tile or block curtain walls, partitions, parapets and facings and brick -chimneys of the present design .should he absolutely pcoin hi teal. Roof should preferably he designed as part of the structural frame and in] any* ease should be so fixed that tlidy' cannot slide off the walls and .inf addition should be braced diagonally on the plane ot the ceiling. . (8) The building as a- unit (and every portion, of it) should be so designed that when under the influence of the maximum acceleration the stresses in any part of it do not exceed ordinary working stresses. The .maximum acceleration suggested for design will givip a horizontal thrust applied at the centre of gravity of the whole (or part) of 1 /sth the weight. .’To visualise: this condition suppose.every part of a building is reduced to I/oth of its actual weight' and then the building hold by its foundation' is turned over it* a horizontal position. . The : ‘stressbs existing are those which would bo caused by the earthquake .and to these must he added (algebraically) the normal stresses, <fl) The distribution of weight up the height of a building should when plotted resemble as far as possible a right pyramid. Heavy stores should he. kept ■as low as possible and the offices should he placed at the ’ top., (10)' On the road frontage all floor's above the ground floor should be set back eat least six feet ;to enable the necessary bracing to he carried down to the foundations at the rear of shoo windows and to protect the main front foundations from .other-, wise unavoidable weakness caused by numerous street excavations. • ‘(11) 'The natural frequency of . vibration of a building (and every part of,it) should be made as high as possible but should not be less than- one rjy'cle per second. Other restrictions, have - been designed to ensure that this minimum will be • exceeded without special analysis. ' - (12)-The use of wood, as an-earth-resisting material cannot' be'ignored biit first-proof buildings slioiild be compulsory 'in blocks. • .Food workmanship is of the -greatest' importance, for a building, being subject to an alternating stress, will soon lose rigidity if bad ' workmanshin' exists and'a:loss of; rigidity will quickly , lead to progressive failure. 1 Every person in New Zealand must do his best to separate past • "fashion’ ’ from * his mind and be prepared to accept vsomething entirely, different—ho must realise- that safety .gomes before appearance, convenience or mere financial pin, •