Monday, June 25, 2012

Tall Buildings and Their Problems, by Herbert T. Wade,

November, 1908, The American Review of Reviews, Vol. 38, No. 5, edited by Albert Shaw, page 577,

Tall Buildings and Their Problems, by Herbert T. Wade,

THE recent announcement that the first skyscraper to be erected in New York City was to be demolished to make room for a larger structure which would rise to a height of thirty-eight stories came at an interesting time, inasmuch as the present year has witnessed the completion in that city of several of the loftiest and largest structures known in the annals of architecture, while at the same time there have been filed with the building department of the city plans for office buildings even higher and greater than those which to-day stand out so prominently on the skyline of Manhattan. It is worth recalling that the first skeleton-construction building, from which the modern high office building has been evolved, dates back only to 1883, when the Home Insurance Company erected such a structure in Chicago. Following this pioneer effort at Chicago came the Rookery, supported by 150-foot vertical columns, and the Tacoma Building, fourteen stories in height and the first to carry its walls on the steel construction. In fact, it was soon realized by architects that by using steel columns and beams, terra-cotta arches in place of the heavier brick, and speedy and safe elevators, strong, useful and serviceable buildings could be constructed to considerable height.

While the Chicago prototype was plain to the extreme in its rectangular austerity, yet when the skyscraper idea was introduced into New York architectural decoration and adornment were deemed desirable and accordingly added, so that to-day the tall building is as much entitled to esthetic consideration as any other form of structural design. But utility has been the governing consideration, and particularly in New York peculiar conditions have led to the construction of skyscrapers in such quantities that within less than two decades the appearance of the lower part of the city has been entirely transformed. But it must be remembered that these structures have been built under building regulations or codes where no limits of height have been provided, save in the case of tenements, and it must be borne in mind also that the impending adoption of a new or revised building code has been an important incentive toward the filing of plans for such a colossal structure as the proposed new Equitable Life Building. Naturally, in building a high office building in such a city as New York, commercial considerations demand that it should be erected at a center where people congregate, and where, consequently, land values are extraordinarily high, and that it should return the maximum revenue by housing as many people as possible.

(The Building Code of New York City allows a maximum foundation pressure of fifteen tons per square foot. Without exceeding this, it would be possible to erect on n lot 200 feet square the huge building shown above. It is 2000 feet high: weighs 516,500 tons: would cost $60,000,000. The wind pressure would he 6,000 tons. It would take eight times this pressure to overturn the structure.)

In other words, given a certain ground area, the problem is to erect a building to afford so many square feet of renting space, and to obtain this the building naturally must contain a certain number of stories and rise to the corresponding height. To the demands of real-estate owners architects and engineers have responded, so that to-day it seems almost vain to look for any limits either on the height or size of buildings if their future usefulness and earning capacity can be demonstrated, assuming of course that municipal regulations will impose no further restrictions than at present. Indeed, the engineer of the Singer Building, Mr. O. F. Semsch, in connection with the editor of the Scientific American, computed the height to which it would be possible to erect an office tower building under the present regulations, and it was found that a 150-storied structure rising to a height of 2000 feet was feasible according to the building regulations now in force in New York City, and with due consideration of modern engineering practice and theory. Such a structure is shown in the illustration. To-day the demand for offices in New York City seems to be fairly well met, and in the best situated and appointed of the modern high office buildings the floor rentals are figured at from $2.50 to $4 per square foot, with a maximum of about $5.

Though it is realized that the unrestricted erection of skyscrapers in a great city cannot go on indefinitely, yet no scheme for the satisfactory regulation of such buildings so far proposed has met with universal approval. By going to greater heights the lower and ground floors, for which artificial illumination for the entire day must be provided in most cases, are made less desirable and useful, yet at the same time in many cities it is believed that the time has passed for a restriction based solely on height. In fact, it has been proposed by Mr. Ernest Flagg,the architect of the Singer Building, that so long as an entire plot is not covered there should be no limit to the height of a tower on a certain specified part, and that this right, where the owner did not desire to avail himself of the privilege of erecting such a tower on his own property, might be transferred to the owners of adjoining lots, so that on each block there might be one or more towers rising to an extreme height, but restricted in their ground area. So many factors, both economic and practical, as well as esthetic, however, enter into the problem, that there seems but little hope of an early and satisfactory solution.


The skyscraper or tower building, in addition to extreme utility, possesses a beauty of its own that can be judged by the same canons that are applied to the older forms of construction. Furthermore, it may be seen that a distinct type has been evolved, and to this recent structures conform with substantial unanimity. An analysis of this type would reveal a massive basement, often of several stories and with an elaborate entrance showing considerable carving, above which successive stories rise in unbroken lines of windows and plain surfaces. On the top stories the decoration is concentrated and at the attic or the lantern of the tower is centered the upper adornment of the structure which is largely responsible for the individual character of the building.


Whatever may be the general design of a modern high office building, its realization is essentially an engineering problem, for, as is well known, the modern skyscraper is a steel cage or skeleton structure fashioned of columns, beams, girders, and trusses of steel in a manner precisely similar to a cantilever bridge. Resting on a firm foundation, which now with extreme heights must go down to bedrock, the structure must carry not only floors and partitions but the exterior walls of brick, terra cotta, or stone. Furthermore, to the structural framework must be added wind-bracing, so that the entire surface exposed to the wind shall be able to withstand pressures far in excess of any it is likely to experience. The standard safety pressure for computing the wind-bracing is taken at thirty pounds to the square foot, which is in excess of that of a violent hurricane at sea or a gale of over seventy miles an hour.


It will be obvious therefore that the foundation is the first and all important consideration, and as a necessary consequence of massive foundations. In New York, on lower Broadway, solid bedrock lies between sixty
and ninety-three feet below the level of the curb, and to this must be sunk the foundations of the modern skyscraper office building. This bedrock is overlaid by from five to eighteen feet of hard pan, which would support a foundation carrying from six to ten tons to the square foot, while above and extending to the surface is material designated as quicksand by the engineers, which is not available where the load is much in excess of three tons to the square foot. Now the bedrock will carry in safety a load from fifty to two hundred tons per square foot, but to reach it through the quicksand for a distance of fifty feet or more below the ground water line or seventy feet below the curb, and through twenty or more feet of hard pan to the underlying gneiss, as was the case in constructing the foundations for the City Investing Building, means that a pneumatic caisson must be used for each individual foundation just as if it were the subaqueous foundation of a bridge. In such a caisson, which is sunk clear to bedrock, a concrete pier or column is formed, and usually there must be a separate foundation for every column or pair of columns, which, resting on ribbed bases of cast iron, rise vertically the entire height of the building. In the case of the foundations for the City Investing Building, already mentioned, the foundation caissons covered approximately 45 per cent, of the plot and were but a few feet apart.


The actual erection of the steel skeleton and the connection of the various parts present no extraordinary difficulties, but it does supply further evidence of the care and complete organization with which every step in the construction of a skyscraper is attended. Naturally on the premises there is little or no storage space, and the use of the streets being prohibited, the material must be brought to the building as required and set almost immediately in its permanent place, the column lengths, braces, and floor beams being hoisted into position and rapidly riveted by pneumatic hammers and oil heated furnaces. The concrete or terra cotta for floors soon follows, and then the fireproofing for columns and beams so that no part of the metal structure is exposed. For here is the crucial point of the high building It must be absolutely fireproof and all parts of the structure must be so covered with tile or concrete or plaster that the heat cannot reach the steel and cause it to expand. And this is the more emphasized when it is realized to-day that every building over ten stories in height must supply its own fire protection, as it is beyond the reach of fire engines, and even the new high pressure must be administered through the standpipes and hose of the building.

From the Architects' & Builders' Magazine.
(This diagram shows the method of constructing the concrete foundation for each vertical column. The caisson on the left has been filled with concrete and the pier rests on bedrock, while the one on the right Is being sunk and the material at the bottom Is being removed.)

After floors and fireproofing come the exterior walls and the ornamental cornices, cupolas, lanterns, etc. which, while adding to the total weight of the building, involve no particular difficulties of construction, though of course affording ample opportunity for decoration and ornament. The New York building code provides that the walls of a steel skeleton building shall be twelve inches in thickness for the upper seventy-five feet of the building height, and below that point shall increase four inches in thickness for each succeeding sixty feet.

The vertical columns in the interior of the building, to which we have referred, possess two very important functions in that certain of them must surround the elevator shafts and to them must be connected the guide rails along which the elevators operate, while in proximity to other columns, but in the best practice in a separate compartment or pipe shaft of terra-cotta or tile, are the electrical conductors for light, heat and power, steam, water, compressed air and vacuum pipes, and the cables carrying telephones, telegraph and time service wires, various outlets, connections and switchboards being provided at each floor.


In the last analysis it has been only the high-speed elevator that has made a practical possibility of the tower building, and successive efforts have culminated in elevators which travel the 546 feet of the Singer Building tower and to the forty-fourth story in the tower of the Metropolitan Life Building. Such a journey in the elevators used but a few years ago would have required from ten to fifteen minutes, which of course would have rendered the upper floors of such a tower unavailable for rental, but to-day even when the speed of an elevator is limited by the building regulations to 600 feet per minute, it is possible to secure safe and speedy service. Indeed, many engineers think that this restriction is a most wholesome as well as liberal provision, and it is so found in actual practice, for it is not the time spent by the car in travel that counts, but that required for the ingress and egress of passengers, amounting often to 75 per cent, of the time required for a trip. Therefore small cars running with moderate velocity are usually more advantageous than large cars of greater speed, while as a result of experience it is stated that one elevator is needed for every 25,000 feet of rental floor space. Now for the requirements of the very high building two types of elevator have been evolved, both of which in actual use have been found satisfactory. These are the plunger elevator, in which hydraulic pressure acts directly on a long plunger working in a cylinder and carrying the car at its extremity, and the cabledrive elevator, which is based on the direct traction principle and is operated by an electric motor.

(The plunger elevator is operated by means of water tinder pressure being admitted to tbe cylinder, this power being applied directly on the plunger through the medium of pilot and main valves controlled by lever from the car. The descent is by gravity, the main valve being opened and allowing the water displaced by the plunger in Its descent to escape to discharge tanks. Counterweights and cables are used only to compensate for the variable buoyancy of the plunger.)



The plunger elevator is an interesting application of a principle that until comparatively recent years had been used for very short lifts only, and it requires a deep well drilled into the ground for the cylinder in which the plunger operates. The most extensive installation of plunger elevators is to be found in the City Investing Building, where twenty-one have been provided, seven of which, operating as express to the seventeenth floor and local to the twentysixth, have a travel of 368 feet, which is a record distance for plunger elevators. To sink the wells for the elevator cylinders over one mile of drilling was required, while the total length of car and counterweight guide rails exceeds four and one-half miles. It is interesting for the non-technical individual to learn that the elevator engineer figures the work done by the cars of an elevator installation on a mileage basis, which in the case of the City Investing Building amounts to 180,000 miles per annum. Furthermore, this involves a pumping plant that would suffice for a city of 200,000 inhabitants, as when the cars are operating on the designed schedule there is an annual delivery of 900,000,000 gallons of water.


With the electric direct connected traction elevator even greater heights are possible, and such machines are found installed in the towers of the Singer and the Metropolitan Life buildings, as well as in the new Terminal Building. In this type of elevator an electric motor usually is placed directly over the elevator shaft above the car, and the cables supporting the latter pass up and over a sheave or pulley, A, mounted on the same shaft as the armature or revolving part of the motor. After passing around a second sheave or idler, C, the cable again is wound around the main sheave and is connected with a counterweight, H, equal of course to the weight of the car and its average load. Now at a normal armature speed of sixty revolutions per minute the circumferential velocity of the sheave, which naturally is the same as that of the cable, is sufficient to insure the desired velocity of 600 feet per minute, while the regulation of the motor by switches and resistances is readily accomplished. Various safety devices are installed, but as a last resort there are oil cushions or buffers for both car and counterweight, which are designed to bring the car to a safe stop from full speed at either the top or bottom of the shaft. Such an elevator in the Singer Building rises in the tower to a height of 546 feet, while in the Metropolitan Life Insurance Building five such shafts will rise to the fortyfirst story and one to the fortyfourth. In the Hudson and Manhattan Terminal buildings there are thirtynine of these elevators, with a maximum travel of 285 feet f o r those rising to the twenty-second story.

For power, light, and heating it is plain that these new office buildings must require large and elaborate steam, pumping, and electric plants located in their basements, and the special mechanical engineering of such a building presents many special problems on account of limited space both for machinery and for coal storage. In the Terminal buildings not only has there been installed a complete power plant, but arrangements have been made to use current from the power-house at Jersey City, a special transformer room having been designed for the sub-basement where the alternating current passing through the tunnel will be transformed into direct for the service of the building.


Just as in the case of the exterior of the new office buildings, the public passageways and halls of the lower stories afford considerable opportunity for interior decoration, often rising to a height of two or three stories and being adorned with marble, carving and bronze, so that their appearance is most attractive. And these halls have a double function, as, in addition to giving access to the elevators, they often serve as public passages leading from street to street, or preferably supplying the approach to elevated or underground railways. Now for a person to be able to step from tube, subway, or elevated platform directly into an elevator naturally 'makes offices in such a building most convenient and desirable, while the large number of people passing through the groundfloor halls or arcades, in addition to the regular occupants of the building, makes small booths or offices most available for retail business. Indeed, so many people are collected in such a structure that such conveniences as special telegraph offices, restaurants, newsstands, book and stationery shops, cigar stands, and shoe-polishing establishments are most essential, not to mention haberdashers, tailors, real-estate agents, confectioners, and the hundred and one other occupations that can flourish where a number of people are gathered together. But withal the character of the building must be preserved, and the ease with which the office of a firm can be found, especially if identified with the name of a building that is on- every one's tongue, makes a recently erected skyscraper a most desirable building in which to have an office, while the various improvements making for comfort and convenience are all appreciated at a time when business must follow the line of least resistance.

In the skyscraper we have simply turned our stream of travel from its normal horizontal to a vertical direction, and we have substituted private streets and modes of conveyance for those of the city below.

Copyright, 1908, by Pach Bros.. N. Y.

(Our photograph shows the tower approaching completion. It has fifty stories, and its flagstaff is 700 feet above the sidewalk. This great campanile to-day is only exceeded in height by the Eiffel Tower In Paris.)


Most notable perhaps is the tower of the Metropolitan Life Building, designed by N. Le Brun & Son, which with its glistening white marble already has become a landmark for the city. As the insurance company desired more space, and as it owned the single corner not occupied by its main building, it was but natural that this vacant space should be utilized in such a way as to add to the dignity of its massive and imposing Italian Renaissance structure. Now no more fitting climax for such a group of buildings could be imagined than this noble campanile rising with its forty-six stories 700 feet above the sidewalk. For a great insurance company to have a home of such a monumental character is no small asset, and the value of such a structure outside of land mortar and stone cannot be underestimated.

Indeed, with its great clock 324 feet above the sidewalk, where hands twelve feet in length point to four-foot numerals on dials twenty-five feet in diameter, and with its four tower bells still higher up and announcing the quarter-hours from a point twice as high as any other chimes in the world, the Metropolitan Life Building long must stand as one of the world's wonders. Here, as in other office buildings, the floor space can be computed in acres, and the entire building, with its grand total of 16,237,034 cubic feet, has a floor area of 1,085,663 square feet, or about twenty-five acres, available for the business of the company or for rental.


Sharing the honors for a high tower building with the white Italian campanile of the Metropolitan Life is the Singer Tower, designed by Ernest Flagg, which, however, suffers in any comparison with the former on account of the lofty buildings with which it is surrounded and the absence of the park at its foot. Here we have a forty-seven-story tower as the predominant feature of the remodeling and amplification of the old Singer Building at Broadway and Liberty Street. This unique structure, sixty-five feet square, sets back fifteen feet from Broadway and in its height of 612 feet carries forty-two office floors, each with sixteen offices. In the Singer Building the walls are of brick and limestone, while copper sheathing is used conspicuously, especially in the tower, where considerable decoration has been employed. The architecture is modern French, and naturally involves greater adornment than in the Metropolitan Tower, yet there is no lack of stability in the general appearance, and the extreme height of the tower is marked by grace and strength. Together with the main building, which is fourteen stories in height and has forty offices on each floor, the Singer Tower supplies about nine and one-half acres of floor space for rental.


Passing from tower buildings to those of somewhat different type, the Terminal Buildings of the Hudson and Manhattan Railroad Company, of which Clinton & Russell are the architects, not only rise to a considerable elevation, twenty-two stories, or 275 feet, above the curb, but they are remarkable as constituting the largest and heaviest structure for an office building in Manhattan. This building really represents two distinct structures, numbers 30 and 50 Church Street, running from Cortlandt to Fulton Streets, though separated by Dey Street, but as they have been built by the same corporation on the same foundation, and as they contain the terminal of the Hudson River tube and form one structure below the street, they are usually spoken of together. Over twenty acres of floor space are available for rental, and the two buildings could be divided into some 4000 offices, with accommodations for 10,000 people, or a population equivalent to that of Sioux Falls, S. D.

This enormous building has been constructed on an immense box of concrete, 420 feet in length and 178 feet in breadth at its widest point, with walls eight feet thick going down to solid rock, an average depth of seventy-five feet below the surface. Now this gigantic box of concrete is pierced so that the trains from the tunnel under the Hudson River can enter through Cortlandt Street and pass out through Fulton Street, the tracks being about thirty feet below street level, while the building proper supplies the necessary approaches to the platforms, ticket offices, waiting-rooms, etc. The terminal arrangements in no way interfere with the use of the portion above the sidewalk as an office building. Indeed, each building above the third story has a floor plan of H-form, so that abundant light and air are secured for the various offices, there being some 5000 windows in the two buildings. While the Terminal buildings have not the ornate exteriors of some of the recent high office buildings, yet they are massive and imposing and carry out effectively their general object.

(These buildings house daily a population greater than that of many a small city. Beneath Is the downtown terminal of the Hudson River tubes.)

(Considered one of the most successful designs for a large office building, as It combines with utility great architectural beauty.)


Another interesting example of a skyscraper is the City Investing Building, F. H. Kimball, architect, with its entrance on Broadway,near Cortlandt Street, and extending through to Church Street,with a frontage on Cortlandt Street. Here we have an office building designed to afford a maximum of rental space and without the necessity of striking architectural features or the consideration of unique conditions. The result has been a rich and artistic building which rises from the Broadway sidewalk to a height of thirty-two stories, or counting from the basement to the tower over 500 feet. The architectural base for the first five stories is faced witli limestone, while above white glazed brick and white terra cotta have been used, and emphasize the opinion of many architects that a single solid color brings out most effectively the mass and form of a skyscraper.

The upper stories and the attic of the City Investing Building show considerable decoration, while within the building the arcade on the ground floor extending from Broadway to Church Street is as prominent a feature of its general plan as it is from a decorative point of view. Here have been concentrated a wealth of artistic adornment, marble, bronze, ornamental plaster, and carved stone being among the materials used. The City Investing Building has a floor space available for renting of nearly eleven acres, and its total cost was about $10,000,000.

The present space does not permit consideration of such important structures as the new West Street Building of Cass Gilbert, the new home of the Trust Company of America, or others almost equally important, but it is desirable to refer briefly to several important projects that seem to indicate that the last word in skyscraper construction has not yet been said.


First of these is the proposed office building for the Equitable Life Assurance Society to be erected on the present building of the company on the block bounded by Broadway, Nassau, Pine, and Cedar streets. The plans prepared by D. H. Burnham & Co. call for a structure of sixty-two stories, 909 feet in height, exclusive of a 150-foot flag-pole, and being 209 feet higher than the Metropolitan Life tower and 292 feet higher than the Singer Building, as indicated in the illustration on page 579. Whether the building ever will be erected may be considered at this moment an open question, but the acceptance of the plans by the building department is of course a great advantage, whether the insurance company decides to erect such a building itself or should wish to dispose of the land with such permission for its construction.

The plans show a building of Renaissance type built in three sections surmounted by a cupola. The first or main building is 489 feet, or thirty-four stories high, or twice the height of the main building of either the Metropolitan Life Insurance Company or.the Singer Building, and will be finished with cupolas several stories in height set around the base of the tower or second section. This will extend from the thirty-fourth to the forty-ninth story in the center of the building, being, of course, of smaller plan, and in turn will be surmounted by a still smaller section reaching to the fifty-eighth story, above which for four stories more will rise the main cupola. The main facades will be of brick and granite with terra-cotta trimmings, while the design shows bays set between pilasters of Corinthian and Doric orders, with clustered columns at the corners.


Less monumental than the proposed Equitable Building is the thirty-eight story building, designed by W. C. Hazlett, to be erected on lower Broadway, to supplant the old Tower Building, to which reference was made at the beginning of this article, as well as to occupy adjoining lots, while a new and lofty structure to take the place of the Mills Building, with a tower 1000 feet in height, has been proposed.


Whether the American city has been justified in permitting the skyscraper to flourish, or whether the American investor in the end will find the lofty tower and the huge office building a useful and profitable investment, time only can tell, but that the American architect and engineer have been able to meet the opportunity which has given rise to these structures admits of no discussion. Not only has a type of building based on pure utility and special conditions been evolved, but an artistic design and treatment has resulted that to-day justly earns the admiration of European critics. And in actual construction no less than in design have American ingenuity and engineering skill been manifest. Structural materials,—especially steel, terra cotta, and concrete,—have been improved, and their use has been developed along scientific lines, so that the construction of a modern skeleton building with due regard to all elements of safety can be carried on with a skill and certainty not excelled in any form of structural engineering. And with the experience of large fires and an earthquake to test his work, the engineer of the modern skyscraper surely can say that he, like his building, stands on a firm and safe foundation.

No comments: