TO RENDER BUILDINGS FIREPROOF

TO RENDER BUILDINGS FIREPROOF

How the New York Building Department Tests All Fire-Resisting Material.

Excellent as is the fire department of New York city, it is powerless to keep down fires altogether, and so long as there are buildings to burn the department will not go out of business. That buildings will increase and multiply as years roll on stands to reason, and in order that these may prove to be less a source of danger it is at least desirable that all should be built of fireproof materials, so far as such are procurable, How imperative this requirement is is proved from the fact that the cost of the buildings now being erected in the borough of Manhattan alone will this year exceed $150,000,000, with the prospect of the ngures for 1003 being still greater. A very large proportion of this money is spent upon skyscrapers, tor the prevention and extinguishment of fires in which very stringent laws exist, both as to the use of fireproof materials in their erection and in their firefighting equipment. “As a rule, the cinder concrete floors consisted of segmental arches of flat ceiling plates, differing only in the form and position of the metal by which the concrete was reinforced or strengthened. In some cases the metalwork formed the centering on which the cinder concrete was laid and left permanently in place. In all cases, the metalwork was placed as near to the lower surface of the cinder concrete as possible, in order that it might bear all the tension caused by the bearing down weight on the floor above. The greatest care is taken in these tests to make them thoroughly trustworthy and practical. A pyrometer, consisting of bars of rhodium and platinum, bound together, in whicu an electric current is generated by the heat and recorded by a galvanometer, registers the temperatures. This method has been generally accepted as a standard throughout the country, and has been incorporated, with slight modifications, into the present building law of the citv of New York. About forty different types of floor constructions have been tested under such conditions and have successfully met all the requirements since the method was first introduced, and most of them are still in general use in the construction of firenroof buildings. As a result of these tests, the fire-resisting qualities of cinder concrete mixed in the proportions of one ot Portland cement, two of sand and five ot hard coal cinders have been well established. Where properly applied, so as thoroughly increase the floor beam, a sufficient insulation has been provided so that no injurious effect results from heat.” Stone concrete is not sanctioned by the building department, any more than tests have approved its use at Hamburg, Germany, where also coarse, hard cinders and concrete mixed find favor. Soft coal cinders do not bind well with the concrete.

With respect to the former: The building department of New York city, under Commissioner Perez M. Stewart, is doing its best to avert a big fire, to which the city is more or less liable at any moment, notwithstanding its fire department and the many firc-resistent buildings that have been put up. In order that the fireproofness may be as complete as possible, the bureau of buildings will not allow the use of any fireproof material until it has been thoroughly tested by experts. The department is perfectly willing to investigate the merits of any new style of building construction, to give it fire and strength tests at the expense of the city, and to permit it to be used, if it is successful in passing these tests but only on that condition. This course was begun in 1805 when Stephen Constable was superintendent of the building bureau under Mayor Strong, when the demand arose for cheaper, lighter, and at the same time fireproof buildings. Supt. Constable instituted a series of tests that should approximate to the conditions that womu obtain in an actual fire. G. C. Henning, the engineer of tests, devised the method of the test. It consisted of placingsay, a proposed form of floor construction on a brick structure about eleven by fourteen feet in size, and ten feet high, in which a wood fire was maintained at a temperature of about 2,000 degrees for four hours. After exposure to fire the floor was then subjected to a stream of water from a fire hose at the pressure ordinarilv used by the fire department in fighting fires. This pressure varies according to conditions: it was, therefore, determined, in order to make the tests uniform, that it should be sixty pounds per souare inch at the mouth of a one and one-eighth inch nozzle. The floor load to be carried during the exposure to fire was 150 pounds per square foot uniformly distributed. On the extinguishment of the fire the floor load was increased to 600 pounds per square foot, so as to determine whether the floor was strong enough to carry its load safely.

“Numerous types of reinforced cinder concrete constructions (says Rudolph P. Miller, chief engineer of the building department) were tested under these conditions in i8q6 and 1897. There was also one type of reinforced stone concrete tested, and a floor of a plaster of paris composition, in which the necessary strength was obtained bv a system of suspension cables. Several types of terra cotta floor arches were also tested.

TESTING BEAMS, NEW YORK BUILDING DEPARTMENT.NEW YORK BUILDING DEPARTMENT OFFICIALS APPLYING FIRE TEST TO FIREPROOF BUILDING MATERIAL.

The extensive use of steel has arisen quite recently with the incoming of the skyscrapers. Previous to 1870 that style of building was unknown, and fireproof construction was practically limited to public buildings, where the question of expense was not considered. Its type was heavy masonry construction, and it was only after the use of wrought iron floor beams spaced at regular intervals supporting segmental brick arches was introduced that building construction approached in form our present methods. Such I beams were first rolled in this country by the Trenton Iron works in 1854. To secure a lighter construction than that of the brick arches, one of arched corrugated iron supporting a bed of concrete was introduced, but it failed of its object. In 1871 terra cotta arches were introduced, as in the Equitable building, at Chicago—the hollow tile blocks being of hardburned terra cotta, without the inner web-shaped partition which gives them strength. The present block, with its interior reinforcing webs, was developed about 1873-74, since which time, except for the introduction of the segmental arched tile construction, which can be used for long spans. ‘The tile arch or “end construction” has now superseded the older “side construction,” and is its superior in strength, without being any more expensive. The same principle is applied to fire-resisting floors. Before 1895 Theodore Hyatt’s floor construction was in vogue. It combined strength, rigidity, fire-resistance, weight, and cheapness with the hollow tile construction then in use. Today concrete, whose strength is reinforced by imbedded metal beams, is used in the construction of floors.

As to fireproof wood: That, of course, is a misnomer—as fire-resistance for a longer or a shorter period is all that can he claimed for such chemically treated wood. It is really almost useless in buildings of the tenement house class, and a too great implicit reliance upon it as an absolute protection against the spread of fire in such structures is a snare and a delusion. As Supt. Stewart says: “It would undoubtedly be better if the use of firenroofed wood could be eliminated entirely from buildings, and the requirements so changed that nothing but incombustible materialscould be used for interior trim in buildings over a certain height. No attempt to return to the use of untreated wood in buildings over 150 feet should be tolerated.” The law should be so amended as to forbid the use of untreated wood in tenement houses or private houses, convents, dormitories, etc., which are often seventy and seventy-five feet high, while the hotel, lodging house, and police station must be fireproof, if over thirty-five feet in height. Yet in the former buildings there live the most helpless and the least resnonsible members of the community—the sick, infirm. aged, crippled, and the women and the children—and these, considering the cubic contents of the buildings, probably in greater numbers than in the hotels. It follows, therefore, that, if they exceed the height prescribed by law for the hotels and other buildings mentioned above, they should likewise be built fireproof.

As to the window shutters: Supt. Stewart would insist unon the use of tinsheathed shutters and the immediate abolition of iron shutters, which, bv warping under fire, afford an entrance to the flames. As to the windows: He would have them with metal frames and dazed with wire glass. In the case of buildings with large windows he would have them protected by water-curtains, and the stairways, if absolute safety is to be provided, should be covered ways outside of the building altogether, senarated from it by brick walls, and. of course, fireproof.

Lastly, to insure the safety of the skyscraper and the dry goods districts, there should be at once established the long talked-o_____ auxiliary mains with stationary pumps to enable burning buildings to be deluged with salt water, when required.

The illustrations accompanying this article (by courtesy of the New York Tribune”) show the buildin______ department experts applying the fire test to alleged fireproof building material; attaching a pyrometer (the heat-measuring instrument) preparatory to testing a partition wall by fire; and testing steel beams and arches.

ATTACHING A PYROMETER, OR HEAT-MEASURING; INSTRUMENT,IN TESTING A PARTITION WALL, NEW YORK BUILDING DEPARTMENT.

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