THE MODERN SKYSCRAPER

Taranaki Daily News, 18 July 1929, Page 17

THE MODERN SKYSCRAPER

HOW IT CAME INTO BEING. Two decades ago there were very few buildings in the world exceeding ten stories. This limit to height was imposed by tke huge foundations necessary to support tall structures. Prior to the twentieth century six'stories were the limit for the buildings. People would not walk up more than six flights of stairs, and as the elevator had not been perfected, tall buildings were impracticable. When lifts made their appearance the height of structures in the large towns increased gradually, until 12-storey buildings were to be found in many cities (says the Cape Times;. It was here that the foundation factor cropped up. The great foundations required to suppoi the masonry of buildings over 12 stories rendered their construction prohibitive. The walls at the base of a 40-siorey skyscraper would have to be 30ft thick, tapering gradually as they went up. Thirty years ago the use of steel in the construction of buildings was practically unknown The weight of a floor of offices had to be supported by both walls' of the floor below, and columns of concrete took up a large portion of the lower floors. It was only the few top stories which provided a reasonable amount of unrestricted space. Supporting columns of steel were then introduced, and buildings were designed on the principle of the human body—a • skeleton of steel taking the place of bones and masonry the place of flesh. The outline of the construction of a modern skyscraper provides scope for the skill of architects and builders engaged ii this highly specialised branch of building. To get down to bedrock for the laying of foundations : s the aim of the engineers. Massive concrete pillars are sunk into the ground until they rest upon solid rock. To these are bolted the steel columns upon which the strength of the building depends. The columns are naturally larger at the bottom of the building than elsewhere, but in comparison with the supports of a non-steel building, this taper is hardly perceptible, being about two inches for every four floors. The steel columns and girders have to support the entire weight of the'building. No weight rests on the brick or stone work, with which the gaps are filled up, and each space between the columns and girders is treated as a separate unit. One of these sections may be removed at any time without causing strain to the building. The filling in of these gaps may be started on any floor, and the bottom floors can if desired be left to the last. In buildings constructed entirely .of masonry, windows are restricted in size, by reason of there having to be sufficient masonry to support the weight of the floors above. The steel framework of the skyscrapers permits large windows being let in wherever necessary. The steel work is prevented from rust and corrosion by tar and tar-paper, and with these absolutely waterproof girders there is no chance of water becoming pocketed between the masonry and the steel. work. As the expansion and construction of steel and masonry are necessarily different, a means of counteracting the movement had to be devised. A special' flexible cement, which allows for contraction, was used with great success. The fact, furthermore, that the walls are divided into numerous small sections tends to cheek the expansion and contraction of the building. Were the whole wall to be built in one solid piece, the contraction would be more noticeable than it is when made up of small sections.