THE LIMIT OF TALL BUILDINGS
IN NEW YORK this would appear to be no less than 2,000 feet, without violating the local building ordinances, we are told by The Scientific American (New York).
This is over two-and-one-half times the height of the Woolworth Building and nearly twice that of the proposed Larkin tower. Such a structure is never likely to be erected, we are told, not because there would be any difficulty, or because of any danger from weight or wind, but simply because of the undue space required for elevators. We read on:
"The maximum height of buildings in New York City is increasing by leaps and bounds. Altho the Woolworth Building, reaching 792 feet above the street, was built in the year before the war, it still retains its supremacy as the loftiest building in the world inhabited by man. The Eiffel Tower, 984 feet, overtops it by nearly 200 feet; but the tower is not a building.
"The era of the towerlike American office building was ushered in by the construction in 1907 of the Singer Building, whose topmost point is 612 feet above the sidewalk. It was designed by Ernest Flagg. Then followed, in 1910, the Metropolitan Building, 700 feet; only to yield the record three years later to the Woolworth Building.
"The question not infrequently asked is 'where is this sort of thing going to stop? Are there no limiting conditions which will prevent the extension of these steel-and-masonry wonders into the heavens?' The popular impression doubtless is that we must soon reach a limit at which the building must necessarily crumble under its own accumulated weight, or be blown down.
"As a matter of fact, the limit upon height comes neither from inherent weakness nor from the effects of the wind.
"With a view to ascertain to what height it would be possible to carry a building, we consulted Mr. 0. F. Semsch, the engineer, who found that, subject to the legal limitation of fifteen tons to the square foot, and on a plot 200 feet square, it would be possible to carry a building up 2,000 feet. Mr. Semsch designed the steel work of the Singer Tower, and the weights and other calculations of this 2,000-foot, suppositional tower were worked out on the same general principles as were used in designing the steel work of that structure.
"The total wind load on one side of this building, when exposed to a heavy gale, would be 6,000 tons, and the center of pressure would be 1,000 feet above the street-level. The layman might well be excused for believing that a horizontal pressure of 6,000 tons applied 1,000 feet above its base must surely turn the building over; but the dead weight of the huge mass is so great, that it would require, as a matter of fact, seven times as much wind-pressure before the building began to lift on its windward side and overturn; for, opposed to the overturning moment of 6,000,000 foot-tons, there would be a moment of stability, due to the weight of over 36,000,000 foot-tons.
"It was the coming of the age of steel that made possible the lofty buildings of today. Before the era of steel, however, some astonishingly tall masonry buildings were erected. Thus, the Pharos lighthouse at the entrance to Alexandria, built by the Romans during their occupation of Egypt, was a massive all-masonry structure over 500 feet in height. In medieval times the cathedral builders raised some wonderful towers and spires. The twin spires of Cologne Cathedral are 512 feet in height, and the single spire of Ulm Cathedral is 525 feet. The loftiest masonry structure in the world is the Washington Monument with a total height of 555 feet.
"Recently, there has been filed with the Building Department of this city by John A. Larkin and his brother the plans for an office tower building that will overtop by 224 feet the famous Eiffel Tower in Paris. This tower stands on a gigantic base eighteen stories high on a plot 250 feet by 197 1/2 feet in its maximum dimensions, above which will rise a central seven-phase tower of ninety stories. There will be two stories below the sidewalk and 108 stories above the street, the total height of the building above street-level being 1,208 feet.
"Structurally considered, the question of carrying the enormous weight of the building was merely one of increasing the mass of steel in the columns to carry, with a wide margin of safety, the enormous weight above. These weights are known, and the matter of determining the necessary sectional area of the steel at any given height in the building is one of straightforward computation. As in the case of every tall building in this city, the stability moment is so much greater than the overturning wind moment, that the building is absolutely safe against any disaster due to this cause. The wind pressure, however, especially in a heavy gale of wind, exerts a strong lateral bending stress upon the steel framework of any building.
"In the case of the Larkin Tower, a great deal of thought has been given to this matter, and a special design for the connections of the floor beams with the columns has been developed, which, in effect, constitutes at each floor, a series of massive and very strong knee-braces. These connections take care not only of the bending stresses but also of the severe torsional or twisting stresses to which a building of this character is subjected."
Source: "The Literary Digest" April 16, 1927