EARTHQUAKE-PROOF.

Hawera Star, Volume XLVI, 21 April 1927, Page 7

EARTHQUAKE-PROOF.

BUILDING REQUIREMENTS

AMERICAN INVESTIGATORS ’ VIEWS.

A plea for buildings constructed so as to resist earthquake shocks, in order that Xew Zealand architects might not be blamed by their descendants for the failure of structures to come out of such an ordeal unscathed, was made at a meeting of the Wellington branch of the New Zealand Institute of Architects by Dr. Bailey Willis, president of the Seismological Society of America. Dr. Willis, who is Professor of Geology at Stanford Univessity, California, is tourinng the countries bordering the Pacific studying earthquakes. Introduced by Mr. Bearn (president of the local Institute of Architects), Dr. Willis said his study was of particular interest to the people of the Pacific, who were bound to take some steps to cope with the problem. Such steps had been taken in California, in order that the disaster which overtook San Francisco in 1900 might not be repeated, while in Tokio, which was bound to be visited by further earthquakes, modern methods of building had met with considerable success.

Dealing with California, Dr. Willis explained that the pressure beneath the great fault, which extended for some GOO miles north and south along the Californian coast, had become stored up in intensity, until it was no longer held back by the friction of the two rock faces, the western face of the fault moving twenty feet in the San Francisco area.

The lecturer pointed /out that earthquakes such as this were characteristic’ of regions in which mountains were growing, as were a number of ranges in New Zealand. In the Kaikouras

and the Southern Alps, for instance, enormous stresses were accumulating, which would give rise to earthquakes, not as accidents, but as part of a regular process. It was to avoid the effect of these that it was absolutely necessary for buildings to be erected according to sound principles. Dealing in some detail with the effect of an earthquake bn a building, Dr. Willis explained that, when the bottom of a structure was moved some three inches, at the rate of more than four and a half miles per hour —as was often, the case in a severe earthquake—strength of construction was absolutely necessary if the the building were to stand up to it. owing to the fact that the top* of the structure moved backwards while the bottom moved forwards. A building which had completed its sway in one • direction in response to the impulse given to its base, ami was beginning to swing back to normal when the second shock was received, would not. stand the strain as well as one which came back again so slowly that it opposed the impulse, partly nullifying its effect. It wps natural that the height of a buildiug should have a bearing on the amount of bracing required. In the United States it was the intermediate building, of eight or nine stories, which suffered the most, both lower and taller buildings having a greater power of resistance. The. old contention that a building which would stand a wind pressure of thirv pounds to the square foot would also withstand an earthquare was not true, as its weight, solidity, and diagonal stability had to be taken into account, as well as its outward wall area. j

The lecturer emphasised that diagonal distortions during earthquakes were jii? important factor. When a biulding was built On a solid rock foundation, it was generally known that if it would withstand a lateral force of ten polecat. of its total weight, at its base it would withstand and ordinary earthquake. Foundations of sandy nature, however, increased the necessary resistance considerably. The problem had an economic side, owing to the fact that a building absolutely earthquakeproof might be of a prohibitive cost. In the battle against earthquakes good weapons could be found in cement of high quality, and architecture that was faithfully correct. Builders of great European cathedrals had realised that every element of the building had to do its share of the work, that every stone was needed, and that none was superfluous. In these structures every column was braced, and every column carried its load. Dr. Willis stated that American methods in building construction were often artificial, steel frame and reinforced concrete buildings being erected with material filling up the spaces between the frames which had no more strength than had a teacup. In Santa Barbara, flan .Francisco, and Toldo, steel frame buildings with brick fillings had been found full of cracks. The greatest point of strain was usually two-thirds up the biulding. and, although the steel frames remained standing, tlie bricks or concrete, not being braced to the steel, often fell out.

Panel walls, in order to have resistance, had to have tensile strength. On this principle Professor Xaito, a Japanese engineer trained in America, had built six reinforced concrete buildings in which the steel- reinforcement had been carried through walls and panels of form one integral structure. Those buildings had successfully withstood severe earthquake- shocks. Nevertheless, Americans frequently violated this principle to-day, the lower stories of a biulding being loft without any lateral bracing. ibr. Willis spoke very disparagingly of the deplorable chicanery of contractors and builders who used mixtures of inferior quality, defeating the intention of the architect. Every building which was now being erected on the Pacific coast of America was lining constructed, as far as finance allowed, so as to withstand earthquake. Plans of the work, and the work while actually in progress, were passed by banks advancing the money, and by insurance companies accepting risks. r lhe estimated cost of thus playing for safety was onlv about S per cent, over that of building in the -aid way. by which the future was left to look after itself. Safety first was always the best policy, in architecture as in other walks in life.