BUILDING STRENGTHS

Evening Post, Volume CXI, Issue 66, 19 March 1931, Page 14

BUILDING STRENGTHS

HAWKES BAY SHAKE

EXPEKTS' VIEWS s

"It is to be hoped that the Government Commission recently set up will enforce the incorporation of earth-quake-resisting features in tho construction of buildings in the future," states Professor Lamb, professor of engineering, in his report to the Auckland' University College Council on the visit paid by 'him to tho earthquake areas in Hawkes Bay, the "New Zealand Herald" reports. "The usual text books on construction or: design cither ignore or only make a passing reference to the effects of earthquake, and at present it is very difficult to obtain sufficient da,ta to guide'an engineer or "architect in the prosecution of designs." Professor Lamb paid particular attention to tho manner in which various classes of materials had withstood the shocks. After noting that wood, while resisting shocks, is too prone to the danger of subsequent fire, ho states: "Brick had been used very extensively for buildings for both businesses and residences, and popular opinion in'the stricken aj-ea is definitely averse to any future use of this material because of tho many failures and loss of life whero brick had been used. Howevqr, many examples of brick buildings wero seen which had withstood the shock equally as well as other forms-of construction. • ' DEFECTS IN WORK. "In a considerable number the failures were unmistakably duo to.lack of adhesion of the' mortar to the bricks,' and also to the weakness of tho mortar itself. Bricks could be picked out from the derjris with perfectly clean faces f rco, from mortar, and in many cases the mortar was so weak that it could be crumbled between one's fingers. Another defect noticed- was that the interior joints' in the brickwork were often devoid of mortar. Buildings showing such bad material and workmanship must of necessity fall when subject to horizontal vibrations, whereas other brick buildings which had suffered littlo from the earthquake showed that sound bricks, good mortar, and faithful workmanship had been used in their "construction.

"Eeinforced concrete buildings havo withstood the sjipcks very well indeed in cases where the building is monolithic and is not a composite building. A notable examplo-of reinforced concrete which survived tho shock was a circular chimney about 30ft high in a timber yard. It was practically the only chimney left standing in Napier. "Steel frame buildings were not common. I came to the conclusion . that they could be built earthquake* proof, but the intense fire after.the shock'had bent and twisted tho steel into the most fantastic shapes and utterly destroyed the. buildings. Composite' buildings showed up very badly, some of the worst failures occurring with this class of structure. " THE FIRE DANGER. "Leakage from gas- arid electricity supplies for the short time necessary i to' start a series of fires seems almost j impossible of prevention, therefore the best method.must lie in the direction of making buildings of sufficient strength to resist destruction due to a shock and also to build in fireproof materials. For large buildings a, well, built steel frame encased in concrete, or an, ordinary monolithic reinforced ' concrcto building having rather more ireinforcement than is ordinarily used, so that tho whole structure is well .. tied together, seem to be almost ideal for the purpose. Other fire-resisting materials may be used, provided all parts are well tied together; floors and roofs should not simply rest on the supporting walls. Wooden buildings of-one or two stories can be built to resist a 'quake, but they should be constructed of timbers framed together and not simply nailed. Of course, they are liable to destruction by lire." Tho result of observations .of the architectural features is contained in tho report of Professor Knight, professor of architecture, and Mr. S. I. Crookes, lecturer in building construction. They state that wooden buildings as a class "stood extremely well, and in those which failed tho absence or inadequacy of bracing below the ground floor was a general feature. Buildings with cither a good reinforced . concrete or structural steel frame, adequately fire-proofed, and having reinforced concrete floor slabs, showed considerable resistance to both earthquake and fire. Structural steelwork, which was not made proof against fire, suffered "very severely,from lire, and-gome of it was damaged by the earthquake. The almost, universal' failure of chimneys in domestic buildings demonstrated the need of a new • type of chimney construction.