F. METAL-SKELETON CONSTRUCTION.

341. METAL SKELETON CONSTRUCTION.] The term "Metal Skeleton Construction" shall be understood to mean that type of construction in which all loads and stresses are transmitted to the foundation by a skeleton or framework of metal.

342. ALLOWABLE STRESSES FOR IRON AND STEEL.] (a) The maximum allowable stresses in pounds per square inch in steel and iron shall not exceed the following:

(b) The allowable compressive stresses in pounds per square inch shall be determined by the following formula:

In the above formula L equals length in inches and R equals least radius in gyration in inches.

(c) In no case shall the allowable compressive stress exceed that given in paragraph (a) of this section.

(d) For steel columns filled with, and encased in concrete extending at least 3 inches beyond the outer edge of the steel, where the steel is calculated to carry the entire live and dead load, the allowable stress in pounds per square inch shall be determined by the formula

L

18,000—70—

R

but shall not exceed 16,000 pounds.

(e) For steel columns filled with, but not encased in concrete, the steel shall be calculated to carry the entire live and dead load. In this case the above formula may be used, but the allowable stress shall not exceed 14,000 pounds.

(f) Stresses due to eccentric loading shall be provided for in all compressive members.

(g) The length of rolled-steel compression members shall not exceed 120 times the least radius of gyration; but the limiting length of struts for wind bracing only may be 150 times the least radius of gyration.

(h) Wherever the live and dead load stresses are of opposite character, only 70 per cent of the dead load stress shall be considered as effective in counteracting the live load stress.

343. BEAMS AND GIRDERS.] The beams and girders shall be riveted to each other at their respective junction points.

(b) At each line of floor or roof beams, lateral connections between the ends of the beams and girders shall be made in such manner as to rigidly connect the beams and girders with each other in the direction of their length.

344. COLUMNS.] (a) If rolled-steel columns are used, their different parts shall be riveted to each other, and the beams and girders shall have riveted connections to unite them with the columns. If cast iron columns are used, each successive column shall be bolted to the one below it by at least four bolts not less than three-quarters inch in diameter, and the beams and girders shall be bolted to the columns. Bolt holes in flanges for connection of column to column shall be drilled.

(b) After the bases or base plates and the columns have been set in place, both shall be protected by a covering of rich concrete, applied directly to the metal, measuring not less than 22 inches thick from the extreme projection of the metal. Said concrete coating shall completely fill all spaces, and shall form a continuous concrete mass from the grillage or other foundation to an elevation 6 feet above the floor level nearest the base plate or column stool.

345. RIVETS AND BOLTS.] (a) In proportioning rivets the nominal diameter of the rivet shall be used.

(b) All connections of steel trusses shall be riveted; and the connections of the steel-skeleton work in buildings more than 100 feet high and in buildings whose height exceeds twice its width shall be riveted.

(c) Whenever it is impossible to rivet connections as herein described, such connections may be bolted, provided the holes are reamed and coldrolled or turned bolts which exactly fit the holes are used in place of rivets, in which case the allowable stress upon the bolts shall be that allowed herein for field-driven rivets.

346. PLATE GIRDERS.] (a) Plate girders shall be proportioned either by the moment of inertia of their net section, or by assuming that the flanges are concentrated at their centers of gravity and using a unit stress such that the extreme fibre stress does not exceed 16,000 pounds per square inch. In the latter case one eighth of the gross section of the web, if properly spliced, may be used as flange section.

(b) The gross section of the compression flanges of plate girders shall not be less than the gross section of the tension flanges; nor shall the stress per square inch in the compression flange of any plate girder of a longer length than 25 times the width exceed

L

20,000-160

B

in which L is the unsupported distance and B is the width of flange.

(c) The flanges of plate girders shall be connected to the web with a sufficient number of rivets to transfer the total shear at any point in a distance equal to the effective depth of the girder at that point combined with any load that is applied directly on the flanges.

(d) Webs of plate girders shall be provided with stiffeners over all bearing points, under all points of concentrated loading, and elsewhere as required by good engineering practice.

347. LATERAL AND SWAY BRACING.] All trusses shall be held rigidly in position, both temporarily and permanently by efficient lateral and sway bracing.

348. STRUCTURAL DETAILS.] All structural details and workmanship shall be in accordance with accepted engineering practice, and shall be subject to the approval of the local or State Building Commissioner.

349. PAINTING.] All metals shall be clean and shall be free from loose rust and scale; and shall be protected by at least two coats of approved metal-protecting paint.

350. CAST-IRON COLUMNS.] (a) The limiting length for cast-iron columns shall be seventy times the least radius of gyration.

(b) Cast-iron columns shall not be used in buildings of greater height than twice the least width, or in buildings over 100 feet high.

351. RIVETED TENSION-MEMBERS.] (a) In proportioning tension members the diameter of the rivet holes shall be taken one-eighth of an inch larger than the nominal diameter of the rivet.

(b) Pin-connected riveted tension members shall have a net section through the pin-hole at least 25 per cent in excess of the net section of the body of the member; and the net section back of the pin-hole, parallel with the axis of the member, shall not be less than the net section of the body of the member.

G. TIMBER.

352. QUALITY OF TIMBER.] Timber used for building purposes shall be sound, well manufactured, close grained, free from wind shakes or from dead, loose, decayed, encased or pitch knots, or other defects that will materially impair its strength and durability.

353. ALLOWABLE STRESSES AND SPECIAL REQUIREMENTS FOR TIMBERS.] (a) The maximum allowable stresses in pounds per square inch on actual sections for timber shall be as following:

Fibre Stress and Tension with Grain:

Douglas fir and long leaf yellow pine
Oak

Short leaf yellow pine

Norway pine

White pine

Hemlock

Compression with Grain:

.

Douglas fir and long leaf yellow pine
Oak

Short leaf yellow pine

700 lb. per sq. in.

130 lb. per sq. in. 200 lb. per sq. in. 120 lb. per sq. in. 80 lb. per sq. in. 80 lb. per sq. in. 60 lb. per sq. in.

(b) The unit stress on timber posts shall comply with the formula:

C equals compressive strength of timber with the grain as given in table, L equals length in inches,

D equals least diameter in inches.

(c) The maximum length of a timber post shall not exceed 30 diameters.

(d) Timber posts shall not be used in buildings of greater height than twice the width of the building nor in buildings over 100 feet in height.

(e) The maximum deflection of any wood joist, beam or girder suporting a plastered ceiling shall not exceed one three-hundred-sixtieth part of its clear span.

ARTICLE XII-REQUIREMENTS FOR DIFFERENT TYPES OF

CONSTRUCTION.

A. FIREPROOF CONSTRUCTION.

359. FIREPROOF CONSTRUCTION DEFINED.] The term "Fireproof Construction" wherever used in this Act, shall mean that type of construction in which all parts of a building that carry loads or resist stresses all exterior and interior walls, all interior partitions, and all stairway and elevator enclosures, are made entirely of incombustible material, and in which all metallic structural members are protected against the effects of fire by coverings which shall be entirely incombustible and slow heat conductors, and which are defined herein as "Fireproof Material." Reinforced-concrete shall be considered fireproof when built as required by this Act.

360. FIREPROOF MATERIALS-DEFINITION OF.] The materials which shall be considered as fireproof are: Burnt-clay brick; burnt-clay tiles; terra-cotta; cement concrete, whether made of stone, gravel or cinder; or any other materials having at least equivalent fire-resisting properties. All the above materials shall conform to the standards for fireproof materials adopted by the State Building Commissioner.

361. INCOMBUSTIBLE MATERIAL.] The following materials shall be considered as incombustible: Any of the fireproof materials described in the preceding section; and in addition thereto stones, metals, plaster blocks, plastering on metal lath and metal studding, wired glass, and other materials, provided all such material shall conform to the standards adopted by the State Building Commissioner.

362. FIREPROOF CONCRETE-CONSTRUCTION.] Reinforced-concrete construction will be accepted for fireproof buildings if designed and executed as prescribed in other portions of this Act, and also in accordance with the following:

(a) The materials of the concrete shall be in accordance with sections 320 and 321 of this Act, and the mixing and placing shall be in accordance with sections 322 and 323 of this Act.

(b) The minimum thickness of concrete surrounding the reinforcing members of reinforced-concrete beams and girders shall be 2 inches on the bottom, and 11⁄2 inches on the sides.

(c) The minimum thickness of concrete under the reinforcing rods slabs shall be 1 inch.

(d) All reinforcement in columns shall have a minimum protection of 2 inches of concrete except as hereinafter provided.

(e) If a supplementary metal fabric is placed in the concrete surrounding the reinforcement, simply for holding the concrete, the thickness of concrete under the reinforcing rods may be reduced by one-half inch, in which case such fabric shall not be considered as reinforcing metal.

363. CINDER CONCRETE.] (a) Cinder concrete may be used as a fireproofing material for encasing steel columns and beams, for filing central spaces in steel members, or for filing above flat or segmental floor arches, and for the embedment of floor nailing strips. Cinder concrete shall not be used for piers or walls carrying loads, and shall be given no credit as carrying loads when used in or around steel columns or beams.

(b) Only clean, thoroughly burnt, steam-boiler cinders, free from matter other than cinders, shall be used for cinder concrete. The cinders shall be

of such size that they will pass through a 1-inch square mesh.

(c) Cinder concrete shall contain one part Portland cement and not more than seven parts of cinders and of sand of the grade specified in section 312. The sand in all cases must completely fill the voids in the cinders.

(d) All steel and metal pipes and conduits enclosed in cinder concrete shall be protected by a coating of cement grout or be plastered with good lime mortar before the cinder concrete is placed.

(e) For fireproof construction, the minimum thickness of cinder concrete covering on structural metal shall be the same as required by this Act for brick or concrete covering for fireproof buildings. In slow-burning or mill construction, the minimum thickness of cinder concrete covering on

structural metal shall be 3 inches on columns and 2 inches on beams, girders and other structural members.

(f) Wherever cinder concrete is used for covering columns, beams, girders or other structural steel members of a building, the cinder concrete covering shall have metal binders of wire fabric imbedded in and around said steel members. If wire is used for said metal binders, it shall not be smaller than No. 8 gage and shall be spaced not less than 12 inches apart along the length of the steel member covered.

364. TESTS OF FIREPROOF CONSTRUCTION.] (a) In cases in which it is claimed that any equally good or more desirable mode or manner of construction, or material or device for fireproofing, other than specified in this Act, can be used in the construction or alteration of buildings, the State Building Commissioner upon written application for a permit for the use of the same, shall have power to appoint a Board of Examiners consisting of not less than three nor more than five members, each of whom shall have had at least ten years' experience as an architect, engineer or builder, who shall take the usual oath of office. The said Board of Examiners shall adopt rules and specifications for examining and testing such mode or manner of construction, or material or device for fireproofing, and furnish a copy of the same to the applicant. The material to be tested shall withstand successfully a fire of two hours duration, rising to 1,700 degrees Fahrenheit in the first thirty minutes and remaining at that temperature for the following ninety minutes. At the end of the two hours the material shall be quenched with at least a one and one-eighth inch stream of water for five minutes, at a nozzle pressure of 50 pounds per square inch. The said Board of Examiners shall notify the applicant to submit the proposed material for such examination and test; and such tests shall be made in the presence of the said examiners or a majority thereof. All expenses of the Board of Examiners in making examinations and tests shall be paid by the applicant; and said Examiners may require security therefor.

(b) The said Board of Examiners shall within ten days after such examination and tests, certify the results of such tests and their decision on the said application, to the State Building Commissioner, who shall in the event of a favorable decision authorized the use of such material or construction as fireproof material.

(c) A complete record of the proceedings and all acts and decisions of the Board of Examiners shall be kept by the State Building Commissioner in his office.

365. ENCLOSING WALLS OF STEEL-SKELETON CONSTRUCTION.] The enclosing walls of fireproof buildings having steel-skeleton construction so designed that their enclosing walls do not carry the weight of floors or roof, shall be not less than 12 inches in thickness; provided, such walls be thoroughly anchored to the steel skeleton; and provided, further, whenever the weight of such walls rests upon beams or columns, such beams or columns shall be made strong enough to carry the weight resting upon them without reliance upon the walls below. Such enclosing walls shall be of fireproof material.

366. SUPPORT OF WALLS AND FIREPROOFING.] The fireproofing material and the walls of a steel-skeleton building shall be separately supported for each story upon the steel frame.

367. FIREPROOF PARTITIONS.] (a) All fireproof partitions shall be made of brick, terra-cotta tile, or plain or reinforced concrete. No such partition shall be less than three inches thick.

(b) All fireproof partitions shall be supported directly on the steelskeleton construction, or on the fireproof floor-arches, or on concrete, or on brick masonry.

(c) If stairs, shafts or elevators are enclosed, they shall be enclosed in fireproof partitions.

368. INCOMBUSTIBLE PARTITIONS.] (a) Only fireproof or incombustible material shall be used in the construction of partitions not required to be fireproof, excepting that frames, casings, doors, sash and the rough carpenter work required for the proper fastenings of such frames, casings, doors or sash, may be of wood. Wired glass shall be used in such partition doors and windows.

(b) All corridor partitions of incombustible or fireproof material in fireproof buildings, shall be supported directly on the steel construction, on