FIRE RESISTING CONSTRUCTION AND ITS DEFECTS

FIRE RESISTING CONSTRUCTION AND ITS DEFECTS

Captain T. P. Purcell

Chief Engineer

This paper, which was printed in the Irish Builder and Engineer, of Dublin, contains many practical ideas on the subject of fireproof construction and fire prevention, from which the following excerpts are taken: For some considerable time great attention has been bestowed on the selection of materials for constructional purposes, and their proper application with the object of producing buildings that are classed as “fireproof.” But I may safely say that the expression “fireproof” has a conditional meaning. No building can be absolutely fireproof. The application of heat for a sufficient time will destroy any material, even the ganister linings of cupolas and smelting furnaces. “Fire-resisting” is a much more appropriate term, although but seldom used, even in the building acts. The great destruction of property and loss of lives from fires that has occurred from time to time, wiping out whole blocks or sections in cities, causing veritable ruin and devastation, dislocating trade and entailing much national loss, has aroused the keenest interest in this question of fire-resistance and protection. Many agencies have been and are now at work in trying to devise better methods of construction, with the ultimate view of minimizing the great risk to life and criminal wasteful loss of property, which may be considered as the accumulated fruits of labor. It is to be hoped that their efforts will lead to the general adoption of better standards for construction in cities generally, and that what has been accomplished in Paris for forty years will eventually apply, at least, to the domestic architecture, in all other cities. In Paris it is a fact that when a fire breaks out in any shop or apartment on the lower floors, the tenants in the rooms above never think of any danger, don’t leave their rooms in consequence, but calmly look out of windows at the operation of firemen below them. For the same reason the damage is usually confined to a single apartment, and the engines and appliances used by the brigade are in general quite small and would be looked upon as useless squirts in Great Britain or America.

The British Fire Prevention Committee, as the title implies, devotes itself to prevention. The committee has adopted an international standard table for fire-resisting floors and ceilings, classed under three general heads:

TEMPORARY PROTECTION.

1,500_____ F. optional load on 100 square feet area.

B. Fxposure of 60 minutes at 1,500° F. optional load on.

A. Fxposure of 45 minutes at 200 square feet area.

PARTIAL PROTECTION.

A, 90 minutes at 1,800 loaded with 112 lbs. per foot on 100 sq. ft, area.

B 120 minutes at 1,800 loaded with 108 lbs. per foot on 200 sq. ft. area.

FULL PROTECTION.

A. 150 minutes at 1,800 loaded with 224 lbs. per foot on 100 sq. ft, area.

B. 240 minutes at 1,800 loaded with 280 lbs. per foot on 200 sq, ft, area.

A special commission, composed of representative members, has also been convened to investigate aggregates for concrete, as to their fireresisting qualities and capability to withstand stresses both before and after being affected by fire.

Buildings may be generally divided into three classes: Domestic. Industrial and Public. The first includes all dwellings and places of restdeuce: the second, offices, shops, warehouses, workshops and factories; while the third would embody churches, schools, theatres, assembly rooms, etc. Only the first two classes will be referred to in these notes. The results of fire generally all over the world have demonstrated amply that no form of construction has yet been devised which has withstood a conflagration; also that metal construction generally, when not fully protected, has been an absolute failure, owing to the great conductivity of iron and steel, with consequent weakening, expansion, buckling and distortion of the supports and beams. Steel, which gains in strength up to 490° Fahr., rapidly diminishes when temperature goes beyond 550°, until it becomes plastic. Steel expands one inch in 28 feet when heated to 500°, and one inch in 14 feet when up to 1,000°. When a dull red heat it is about 1,300°. The moral is—don’t let any constructional steel work attain 500°; have beams as short as possible, and disconnected at junctions and bearing points. In the City Market fire, which occurred in 1894, long strings of girders supporting the roof were bolted down on metal columns provided with heavy cast-iron cantilever brackets on each side and similar brackets under the ends fixed into the walls; result was that these walls were early in the fire pushed completely outwards by the expansion, thus giving the fire access to the backs of all the shops surrounding the markets. Up to a quite recent period buildings constructed of iron or steel were considered and classed as “fireproof.” but many serious examples of failure has dissipated the idea. A warehouse on Camp street, Philadelphia, built entirely of iron, was considered fireproof, until a fire occurred and the stock of furniture burned; the fire proved a terribly hot one, the heat being unsupportable 60 feet away, and the building collapsed. Newhall cottcn mills, Burnley, had solid concrete floors between iron girders: expansion of the beams caused complete collapse, with the loss of a fireman’s life. In the great fire at Melbourne, 1898, a block of warehouses covering 380×180 feet, belonging to various owners (one being nine stories high), was consumed, with the exception of the Mutual building, which stood partly in center of block. This was properly constructed—had fine gauze wire outside shutters to the windows; the building was saved, standing up in the midst of so much desolation, a monument to forethought and careful construction. Stone in every form when exposed to fierce heat has given way coniplctely. When used in stairs it cracks and fails rapidly, if exposed to such heat as would be drafted up a stair well, owing to the unequal expansion due to the portion fixed in wall keeping cooler.

CHIEF T. P. PURCELL, DUBLIN FIRE BRIGADE.

Good stock brickwork in honest mortar appears to be the best all-round material for the shells and internal walls of buildings from a fire standpoint. An investigation of the ruins after the great Cripplegate conflagration in London revealed the following results to the Kent Brickmakers’ Association, who caused it to be made:

Ordinary Stick Bricks.— Uninjured.

Perforated Bricks.—Broken to pieces, and when used on outside faces the fronts were gone.

Blue Bricks.— Faces gone.

Red Bricks.—Faces gone, bricks practically destroyed.

Stone.—Cracked and destroyed.

Iron Girders.—Twisted and curled up.

Wooden Beams.—Charred, but practically uninjured otherwise.

Match Boarding.—All burned away.

Terra cotta is hard; it splinters and flies, while the porous sort stands fire better, but is difficult of practical application. Tile construction with toggle joints, largely advocated some twenty years ago and much used in America for fire protection since, has proved insufficient to protect the steel framing, and unsuitable on many occasions, as the tiles crack and peel off, exposing the bottom flanges of girders, upright columns, etc., to immediate distortion, and leading to the final destruction of the building. Previous to the great Baltimore fire, buildings of structural steel construction so protected were regarded as fireproof, but they came badly through the ordeal. The fine Parker building, twelve stories high, which I saw while being erected in New York, was entirely of steel construction protected by tiles, and was almost completely destroyed, or at least badly wrecked, by fire about a year ago, several firemen being killed by collapse of the floors. In America a bitter controversy has raged between rival interests in the building materials line as to, among other mattors, the relative merits of tile and concrete construction in the larger cities, particularly New York, for sky-scraping steel structures, and several efforts to amend the building laws so as to make them more rational and effective have been frustrated by the powerful influence of interested individuals. This sort of operation, though not altogether confined to the states, is, as we well know, fairly typical of America. However, I am informed by R. Humphrey. C. E., engineer in charge of the Structural Materials Laboratory of the United States Geological Survey at Philadelphia, that concrete must gain its rightful recognition and force ahead from this forward. Mr. Humphrey was visiting cities in Europe with the object of studying the building systems, bylaws, etc., in operation, and came to Dublin for this purpose. In face of all these facts you will be surpriseel when I tell you that in actual practice, from a fireman’s point of view, what is known as slow burning mill construction, viz., brick walls, strong uprights of oak or solid pine, beams of sound seasoned wood having a sectional area of not less than one square foot, joists 9×4 or 11×3 and flooring 3 inches thick with tongued and grooved joints, soffits plastered on metal lathing with reliable mortar well haired and forming a good key, for warehouses and a similar but lighter floor construction for dwellings with sound proof pugging between joists, is practically the safest and best type of building out. If in warehouses or factories the stairs is in an outside enclosure, and no belt races or lift holes cut through the floors, firemen will penetrate such buildings with confidence, work close on to the fire, and if the stock of material is not really inflammable or too congested, or that the fire did not get too much headway before discovery, they will do good work, prevent total destruction, and will not allow the fire to spread to neighboring buildings, simply because the men have confidence. The timber may char badly. but won’t collapse until entirely consumed; it does not warp, and so long as any tangible vestige of beam or joist remains it may be walked over. But in so-called fireproof structures, where iron or steel is largely concerned, we look upon them with suspicion, and don’t take too much risk, if we know it. Jn the case of such slow burning buildings, it is, of course, absolutely necessary that all timber is thoroughly seasoned, else dry rot sets in, and such spongy condition invites fire. Quite recently a large factory in the east side of New York, which was constructed slow burning, got on fire; it had seven floors and a big depth from front to rear. A hard fight was made to save it. but the experienced officer in charge of the brigade noticed that, contrary to all custom, the timber floors began to collapse and fall down early in the fray—result, total destruction. This circumstance appeared so curious that the professor of engineering in Columbia University. who tests all materials for city departments. was asked to investigate, when he found that the 16-inch square oak columns supporting the lower floors and 14-inch pine the upper ones must have been put in green originally and were quite closed for about 3 feet under the metal flanged caps, and burned away readily for that distance. The socketed metal caps prevented any vent or circulation of air to the sap pores hence the failure to dry out or season. Great floor areas and cubical capacity without any vertical shaft to relieve the pressure of gases and the consequent accumulation of heat are danger_____us to surrounding property. Lateral spread of fire is much more destructive than vertical. Although vertical openings through elevator shafts and skylights increase the draught, making the fire burn more vigorously, and in a sense hastens the destruction of the particular section on fire: yet the damage, as a rule, is generally less, and the tendency to a conflagration very much reduced, if the fire brigade are there with proper equipment to fight it, as they can usually work in closer quarters with such a fire. While, if these large areas are confined down with fire-resisting floors, the lateral spread of heat is so great that men cannot approach sufficiently close to do effective work, and great risk of spreading ensues. Owing to the exigencies of modern business methods, the necessity for economizing space, also for strong, tall buildings, the free use of steel is rendered more or less an absolute necessity in building construction nowadays. Steel now made cheaply in such excellent quality and convenient sections, giving maximum of strength with minimum of weight, offers great facilities for such construction, but owing to its great power of readily absorbing heat by conduction and rapidly losing strength when exposed to fire it is absolutely necessary for safe construction that it be fully protected throughout by being covered cr embedded in some good non-conducting and fire-resisting material. Good Portland cement concrete is, perhaps, the best medium for this purpose, as, besides protecting the steel, it readily lends itself to moulding into suitable forms and adds considerably to the stability of the structure. Steel in concrete must be amply protected by a proper thicknes, not less in any place beneath a flange or on a column than 2 1/2 inches outside the metal, as, although the expansion of both materials fairly coincide, the concrete has powers of absorption, while the steel has great conductivity.

*****

The rapid application of reinforced concrete, particularly in America, is largely owing to its behavior in the great conflagration in Baltimore and San Francisco; in the latter city it also withstood the effects of earthquake very well. For instance, the Great Fairmont hotel cost $.3,000,000, designed by an Irish engineer to withstand stresses acting upwards from beneath (a most unusual provision), was executed in ferroconcrete, stood in the line of fire, the contents were completely cleaned out, but the fabric withstood both the shocks and effects of the lire and had only to be re-trimmed and decorated to be lit for occupation again. A competitive test carried out in America in 1897, between a concrete floor supported by arch of same material with steel rods, and a similar structure of hollow tiles, the floors loaded to 1.70 lbs. per square foot, and fire kept lighted under for five hours, the temperature being 2,300° Fahr., a beat beyond the melting point of copper and near that of castiron, was afterwards cooled with water and then loaded to 600 lbs. per square foot. The hollow tiles gave way.

*****

The main points in “tire-resisting” buildings, after proper provision has been made and a good margin of safety allowed in the carrying capacity of wall, stanchions and floors, is to see:

  1. That all steel is thoroughly protected, no matter where placed.
  2. That it is protected by good Portland cement concrete of proper aggregate.
  3. That all internal and external angles on the concrete are rounded.

The ideal fire-resisting building:

  1. Should be proof against attack from without.
  2. The internal framing and fixtures thoroughly protected by fire-resisting materials.
  3. It should be able to localize a fire and confine it to the particular floor or apartment where it originates.

Building laws for cities ought to make it imperative that where residential quarters are included over shop or warehouse, the intervening floor should be properly constructed of fireresisting materials thoroughly from wall to wall, with no lateral or vertical opening communicating with upper stories, and that the stairs protecting the domestic part be enclosed by walls and independent of those used for business purposes.

For domestic buildings, the following conditions might be observed:

  1. Steel beams avoided as far as possible, but where necessary for large spans should be thoroughly protected.
  2. Steel joists, if used, should have bottom flanges protected, and not more than 6 feet apart, except where expanded metal is used in the aggregate.
  3. A better quality of concrete and less of it

than usual, spans may be arched to say 2 inches thick at the crown, and a flat ceiling put in on suspended expanded metal, leaving an air space and sound excluder.

This system not advisable if gas is used in the building, as a leak may accumulate and cause an explosive mixture.

4.Plastered ceilings should be of a character that will not fall away as a result of fire.

Note.—When steel joists of small section are embodied in concrete floors 18 inch to 9.4 inch centers, the concrete and plastered ceiling immediately below them usually crack, producing a very bad effect.

.7. Properties aimed at in fire-resisting floors for domestic buildings should be: 1. Resistance to fire. 2. Non-conductivity of sound. .3. Lightness compatible with safety. 4. Economy of space. 5. Economy in cost.

Projecting shop fronts are a great danger to those living above them, except the roof is constructed of fire-resisting material, and that a similar first floor extends beneath the residential part of the building; also that the stairs be isolated from the shop by walls, with a clear exit into the street. A majority of buildings, even under the by-laws now in existence, are only a kind of enlarged grate in which the contents may be rapidly consumed. What with enlarged window openings, fitted with timber frames and the glass, wood boxings, trimmings and casings, unprotected skylights, lift openings which act as flues, belt races and other openings through floors which create draughts, the spread of fire is rendered more certain. At least, efforts can be made to diminish the chances of fire and delay its progress, prevent its passage from room to room, or house to house, to construct so that the fire may be easily extinguished and to provide safe means of exit for the inmates. Party walls, except for narrow buildings, ought not to be less than 14 inches, should have no openings and be carried above roof, in the case of dwellings, say, 15 inches, and of the warehouse class 36 inches higher. All windows in the latter buildings which look into lighting wells, or arc in proximity to those in other buildings, should be protected by some approved form of fire-resisting shutter or have wired glass glazed in metallic frames. Skylights should also be glazed in similar manner. These precautions will delay passage of fire either out of or into the building so protected. Skylights ought, however, be balanced so as to fly open when the fusible fastening is affected by a fire within, and thus relieve the pressure of smoke and heated gases from the building. Partitions of lath and plaster should be abandoned, and either breeze concrete or some of the other approved forms of light fire-resisting partitions used. In cities, flat roofs should be more generally adopted. It is remarkable how readily the timber under ordinary high-pitched slated roofs ignites by radiated beat In in big fires in adjoining buildings. From an .•esthetic point of view, I think the skyline effects would be rather improved than otherwise by nice parapets over flat roofs in cities. Flat roofs will be found convenient in many ways—can be made fireproof against burning sparks or embers, and afford splendid advantages to firemen when fighting any large fire in the vicinity. No presses or lock-ups should be allowed under stairs, as they are often hiding-places for neglect, and fires frequently breakout there, either burning the stairs or rendering it impassable with smoke. Match boarding as well as ceiling lining with air spaces behind. or any passages communicating from floor to floor, are very dangerous in shops and warehouses. as fire is spread rapidly thereby all over the building. In Glasgow a large block of warehouses finished with match boarding, during a strike of plasterers, was recently completely destroyed. although opposite the central fire station; the latter fine building was seriously damaged by the collapse of the warehouses as well as from the intense beat. In dwellings the single stairs ought to have straight flights with flat landings without winders, and be continuous from ground floor to top. This is most important. A dormer or trap door to roof, with a permanently fixed or hinged stepped ladder. This should have automatic fastenings and never placed over the stairs, where it would act as a flue when opened, but in a room immediately off the top landings. For warehouses, workshops and factories more ample provisions must be made, the latter being compulsory under Factory Act. An alternative means of egress from every workroom or section of a factory, either by outside balconies, stairs, bridges to other buildings, etc. If within the building, a factory stairs should be of fireresisting material, enclosed by walls, lighted and ventilated through the outer wall, and the exits from rooms should be closed by self-acting fire doors opening on to flat landings. If external iron stairs, to be carried down by some flank or blank part of the wall free from crossing the windows. All such stairs to have grip rails on wall side, and if over 5 feet ti inches on tread a dividing rail down the center. If iron or fixed sashes are used, a part should be made to open, so as to permit rescues by the firemen as well as entrance with their hose. In a Brooklyn celluloid factory, two months ago, the owner and his son, together with several employes, were roasted to death, in view of frantic but powerless efforts made for their release, owing to window bars which could not be removed, even by the appliances and staff of an adjoining engineering works. Outside concrete balconies afford the greatest possible safety to inmates in case of fire, hor churches, schools and meeting-houses, where large numbers assemble, more ample means of egress ought to be provided than is generally the case. All doors should open outwards and passages gradually widening toward the street. The risk is really greatest from panic, and not so much from fire or suffocation. A sort of temporary madness takes possession of an audience in trying to escape, often from imaginary danger; all are bereft of reason for the time being, and with no other thought than their individual safety. Of course, the furniture and contents in any ordinary room generates a lot of smoke and considerable heat, but it is easily possible in a proper fire-resisting building to limit the damage to the contents and perhaps windows of one room, if the door is only closed when the outbreak occurs. But in the case of shops and warehouses, the counters, shelving and fixtures furnish a great deal of fuel, and the inflammable character of the stocks adds considerably to the fury of such an outbreak, and it is quite possible that the whole contents may in consequence be destroyed, regardless of the fire-resisting qualities of the building. However, the struc jure itself should come through such an ordeal if properly designed and constructed, and the skeleton be again capable of continued use without any fundamental repair. I have witnessed such a case in Glasgow, where fire coming through the windows from an adjoining shop cleared out the stock of a wholesale warehouse of seven floors, without any tangible damage to the floors in the building. As fires may smoulder on and break out during the night, it is of the utmost importance that automatic means of detection and giving an alarm be installed in every important building, whether used for public purposes or business. By such early detection only can damage to buildings and loss of contents be minimized, as well as danger to life averted.

Binghamton Eire Report.

A recommendation that the matter of motorpropelled fire apparatus be thoroughly looked up before purchasing any more horse-drawn apparatus is embodied in the eighteenth annual report of Charles N. Hogg, chief of the Binghamton, N. Y., fire department. During the past year the department has responded to 121 alarms of fire. Of this number of alarms, 76 were calls for tires in wooden buildings, 32 in brick or stone buildings, 10 for other than buildings, and 3 false alarms. The total loss was $45,810.57. of which $16,103.22 was on buildings and $29,707.35 on the contents and the amount of insurance paid was $44,299.85, of which $15,054.50 was on buildings and $29,245.35 on the contents. The apparatus consists of one automobile for use of the chief, one first-size Nott engine, one second-size La France engine, one fourth-size La France engine, one Seagrave city service truck, one Hayes aerial truck (held in reserve), four combination chemical and hose wagons, three ordinary hose wagons, three supply wagons and three chiefs’ buggies.

The month of January, 1910, has a good fire record. The losses during January in the United States and Canada aggregated $15,175,400, against $22,255,000 in the same month of 1909, and $29.582,000 in the first month of 1908. It shows the smallest fire losses of any January in a number of years.

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