war =s±±±SS^= DEPARTMENT OF BUILDINGS THE BUI G CODE OF THE City of Cleveland, Ohio TITLE X REINFORCED CONCRETE CONSTRUCTION V. G. MAR AN I, Inspector of Buildings D. W. MORROW, Ass’t Insp. of Buildings J. P. CROSS, Engineer of Construction REVISED DECEMBER 13, 1911 W. R. Smellie Printing Co. Caxton Building Cleveland 27ja)5 A L t) l 1 The part of the Building Code, known as Title X — Reinforced Concrete Construction, which is here in- eluded as Sections 448A to 473 inclusive, was pre- pared as a separate instrument under the able direction of Virgil G. Marani, C. E. ; Inspector of Buildings, largely by James P. Cross, C. E. ; Engineer of Con- struction, with the assistance of David W. Morrow, B. S. ; Assistant Inspector of Buildings. This important work is the result of much study and research, combined with the experience of en- forcing the present regulations, pertaining to Rein- forced Concrete Construction. A great many engineers were consulted, as well as the committee appointed by the Builder’s Exchange and the Honorary Advisory Committee of the Build- ing Department. Acknowledgment of assistance is given to the fol- lowing Civil Engineers : B. L. Green, C. E. ; S. W. Emerson, C. E. ; W. J. Watson, C. E. ; H. E. Mer- tens, C. E. ; and W. O. Henderer, C. E. The entire work was presented to the Honorary Advisory Commission of the Building Department, and J. W. Frazier, C. E. ; Secretary, gave valuable assistance and suggestions. ^This revised portion of the Building Code was first accomplished because of its importance; but, is only a beginning of the efforts put forth in the past two years by Virgil G. Marani, C. E. ; Inspector of Build- ings, to thoroughly revise and recodify the present code. v... Mr. Virgil G. Marani, Inspector of Buildings, Cleveland, Ohio. October 7th, 1911. Dear Sir : This is to notify you that at a meeting of the Advisory Commission, held October 4th, at 2 P. M., the proposed revision of the reinforced concrete sec- 1 tion of the Cleveland Building Code, submitted by you, was carefully gone over by them. The followinig is an abstract from the minutes of that meeting. “A motion was made by Mr. Striebinger, seconded by Mr. Werk, instructing the Secretary to advise Mr. Marani in writing that the Commission has examined the proposed revision of the reinforced concrete sec- tion of the Cleveland Building Code, prepared and submitted by the Buildipg Inspector, that same meets with their approval and they recommend that Mr. Marani submit it to the Council at its next regular meeting, with the request that they take action upon same at an early date.” Yours very truly, (Signed) J. W. Frazier, Secretary,. 2 ORDINANCE NO. 22783. AN ORDINANCE to ammend Title X, Concrete Construction, Sections 448, 449, 450, 451, 452. 453, 454, 455, 456, 457, 458, 459, 460, 461, 462/ 463, 464, 465, 467, 468, 469, 470, 471, 472 and 473 in- clusive of the Revised Ordinances of 1907, Build- ing Code, relating to the erection of Concrete Build- ings and Structures. Now, therefore, be it ordained by the Council of the City of Cleveland, State of Ohio, that : Section 1. That Title X, Concrete Construction, Sections 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472 and 473 inclusive of the Re- vised Ordinances of 1907, Building Code, be amended to read as follows: TITLE X. REINFORCED CONCRETE CONSTRUCTION. — Index — Section 448 (A). 448 Reinforced Concrete — Definition. 449 Requirements for Drawings. 450 Reinforced Concrete Unit Stresses. 451 Designs for Slabs — Beams and Girders. 452 Limiting Width of Tee Beams. 453 Web Stresses. 454 Square and Rectangular Slabs. 455 Flat Slab Type of Construction. 456 Reinforced Concrete Columns. 457 Spiral Reinforced Columns. 458 Structural Steel Columns Encased in Concrete. 459 Column Splices. 460 Curtain Walls in Skeleton Construction Build- ings. 461 Minimum Thickness of Slabs. 462 Fireproofing. 463 System. 464 Proportions ‘for Mixing Reinforced Concrete. 465 Cement Sand and Inerts. 466 Steel in Concrete. 3 467 Placing Concrete and Steel. 468 Freezing Weather. 469 Centering and Forms. 470 Inspecting and Tests. 471 Concrete Block Construction. 472 Tests of Concrete Blocks. 473 Requirements and Conditions of Approval — Revocal of License. TITLE X. REINFORCED CONCRETE CONSTRUCTION. REINFORCED CONCRETE— DEFINITION. Section 448 (B). By reinforced concrete is meant concrete in which steel is imbedded in such a position that it shall resist all tensile stresses and assist in the resistance of shear along proper structural lines so that the stresses in the combination can be ascertained by computation and verified by tests. The concrete shall be mixed in such proportion and so handled that after it is placed in the forms, all voids in the aggregate will be filled with mortar and all voids in the mortar filled with cement. Thirty (30) days after mixing, it shall develop a crushing strength of two thousand (2,000) pounds per square inch, by testing a six (6) inch cube. REQUIREMENTS FOR DRAWINGS. Section 449. Before a permit shall be issued for a reinforced concrete building or structure, complete working drawings, details and specifications shall be filed with the Department of Buildings, giving the size and location of members, the size and position of reinforcing rods, stirrups, bent rods and any other information necessary for the proper calculation of the structure or building. The Department of Build- ings reserves the right to demand that the owner, architect or engineer submit a certified copy of such computation or stress sheets for examination upon ap- plication for a building permit. The Department of Buildings, in granting a permit to erect any reinforced concrete structure, does not, 4 in any manner, pass the construction until after tests have been made of the actual construction to their satisfaction. REINFORCED CONCRETE UNIT STRESSES. Section. 450. The following unit working stresses shall not be exceeded : Iron in Tension Medium Steel in Tension... High Carbon Steel in Ten- sion Cold Twisted Medium Steel in Tension ] Steel to resist diagonal Ten- sion 1 Concrete in Direct Com- pression Concrete in direct Com- pression (Spiral Reinforced Columns) Concrete-Extreme Fibre in Compression (As determined by the straight line formula) Rond stresses for Plain High Carbon bars Bond Stresses for Plain Low Carbon Bars Bond stresses or Twisted or Deformed Bars . . . . T Concrete in Diagonal Tension NOTE — The compressive : not exceed the product of the compressive stress in the concrete multiplied by the elastic modulus of the steel and divided by the elastic modulus of the con- crete. 12,000 lbs. per sq. inch. 16,000 lbs. per sq. inch. 18,000 [ lbs. per sq. inch. 18,000 lbs. per sq. inch. 10,000 lbs. per sq. inch. 500 lbs. per sq. inch. l 650 lbs. per sq. inch. L 700 k lbs. per sq. inch. i 50 lbs. per sq. inch. 70 lbs. per sq. inch. 100 lbs. per sq. inch. 40 lbs. per sq. inch. stress in the steel shall DESIGNS FOR SLABS, BEAMS AND GIRDERS. Section 451. All reinforced concrete work shall be designed in accordance with standard engineering practice and the following assumptions : That the ratio of moduli of elasticity of concrete to 5 steel is one (1) to fifteen (IS) ; That the adhesion of the concrete to the steel makes the two materials act together; That tensile stresses are taken by the steel and that the stress strain curve of concrete in com- pression is a straight line. Beams, slabs and girders shall be calculated as con- tinuous unless constructed so as to act as simple beams. When continuous for uniform loads, the bend- ing moment at the center shall be figured as not less WL WL than for the intermediate spans and — 10 9 for the end spans, provided at least sixty-six (66) per cent, as much reinforcement is provided at the top over supports as at the center of the member ; and the reinforcement extends beyond the support a suffi- cient distance to insure proper bond. In all cases, however, beams and girders which are built monolithic at the supports shall have at least twenty (20) per cent, as much steel in the top over supports as at the center. For concentrated loads on continuous beams or girders, the bending moment at the center shall be calculated as for a simple beam and this moment may be reduced twenty (20) per cent, for intermediate spans or ten (10) per cent, for end spans. Where a short span adjoins a long span and one- half (y 2 ) of the short span considered as a cantilever cannot produce a bending moment which will develop the strength of the reinforcement over the supports, the long span shall be considered as an end span. For simple girders, beams or slabs the span shall be taken as the clear span and for continuous girders, beams or slabs, the span shall be taken as the distance between centers of supports. LIMITING WIDTH OF FLANGE IN TEE BEAMS. Section 452. When beams are made monolithic with the floor slab a portion of the floor may be as- sumed as acting in flexure in combination with the 6 beam. The width of the slab so acting in flexure is to be governed by the shearing resistance between slab and 1 beam, but limited to a width equal to one-third ( — ) - 3 of the span length of the beams between supports and also limited to a span length of three-quarters (J4) of the distance from center to center between beams. No part of the slab shall be considered as a portion of the rib, unless the slab and rib are cast at the same time. Where reinforced concrete girders support rein- forced concrete beams, the portion of the floor slab acting as flange to the girder, must be reinforced with rods near the top, at right angles to the girder to enable it to transmit local loads directly to the girder and not through the beams. WEB STRESSES. Section 453. Where the diagonal tension exceeds forty (40) lbs. per square inch, additional web rein- forcement of approved design shall be used. Stirrups shall not be placed further apart than two- 2 thirds ( — )D. if they are considered as adding to the 3 shearing resistance. In no case shall the shear ex- ceed one hundred and twenty-five (125) pounds per square inch. When reinforcement is used to increase the unit shear, the proportion of the unit shear taken by the concrete shall not exceed forty (40) lbs. per square inch, and the reinforcement shall be sufficient to take the remainder. If unattached stirrups are used they shall pass under the main reinforcing bars. There shall be sufficient anchorage to develop the stirrups above the neutral axis of the beams without exceeding the bond stresses specified. If the stirrups are attached to the reinforcing bars the connection must be sufficient to develop the elastic limit of the 7 steel without causing slipping along the main bars. If the reinforcing rods are bent to approximately forty-five (45) degrees and are spaced no further apart than “d” or if the bars are bent at the one quarter ( T 4) points, they may be figured as shear members in providing for the excess shear over forty (40) pounds per square inch. The notation “d” shall be effective depth. SQUARE AND RECTANGULAR SLABS. Section 454. For square slabs with two way rein- forcements, the bending moment at the center of the W L2 slab shall be not less than for intermediate 20 W L2 spans, and — for the end spans. 18 The moment over supports shall be not less than W L2 and the sum of the moments over one sup- 30 port and at the center of the span shall be taken not W L2 less than , in which above formula “W” is the 10 load per linear foot and “L” the length of span. For square or rectangular slabs the distribution of the loads in the two directions, shall be inversely as the cubes of the two dimensions. FLAT SLAB TYPE OF CONSTRUCTION. Section 455. The type of construction referred to in this section is a design of reinforced concrete slab supported by reinforced or structural steel columns * with flaring heads and in which beams and girders are eliminated. This construction shall be figured with a bending moment in any quadrant over the column head of not W L3 less than in foot pounds, in which W equals 27 8 total weight per square foot, dead and live load. L equals length in feet of a side of an equivalent square in rectangular panels and the side of a square in square panels. This length shall be taken center to center of columns. In calculating the required area of steel in each band at the center of the span*, the length of span of band shall be taken center to center of columns in the above formula. The bands of rein- forcement shall be made approximately seven-six- 7 teenths ( — ) L in width, in solving for the required 16 area of steel over the column head, the distance from the compressive face to the plane of steel assumed shall be from the center of gravity of all the steel to the under side of slab. Any additional steel required over the column head shall extend beyond the center of column a distance not less than three-tenths (.3) L in all directions. The radial bars may be assumed as resisting tension provided they are carried a distance horizontally not less than one-tenth (.1) L each way before bending downward; further, that the allowed area of each radial bar figured to resist tension shall constitute not over one-half (J4) the area of any single band of continuous reinforcement. The diameter of interior spirally reinforced con- crete columns shall never be less than one-thirteenth 1 1 ( — ) L for floors, or one-fourteenth ( — ) L for roofs 13 14 and the diameter of column head shall never be less than two-tenths (.2) L and this head if constructed of concrete shall be dropped below the under side of slab at least three (3) inches at the outer edge. Square panels shall never be less in thickness than 1 one forty-fifth ( — : ) of the diagonal distance from 45 center to center of columns, for floors, and not less 9 1 than one-fiftieth ( — ) for roofs. SO Rectangular panels shall never be less in thickness 1 than one forty-fifth ( — ) of the diagonal span of an 45 equivalent square center to center of columns for 1 floors, and one-fiftieth ( — ) for roofs. SO The minimum thickness of slabs shall be six and 1 one-half (6 — ) inches for floors and six (6) inches 2 for roofs. The required percentage of steel in a single layer of bars shall not exceed forty-four one-hundredths (.44) of one per cent, for medium steel, or thirty-six one-hundredths (.36) of one per cent, for high carbon steel. In any flat slab type of construction provision shall be made to take care of circumferential stresses. In all buildings hereafter to be erected all interior columns shall have spiral and vertical reinforcement or shall have columns built of structural steel encased in concrete and the slab steel shall be so placed that it comes near the top of slab at the columns and shall be held firmly in position in such a manner that the bars cannot be displaced. A spacing and clamping device satisfactory to the Department of Buildings shall be used for the floor slab steel. In end or wall panels in which wall columns of rein- forced concrete with heads are omitted, allowance shall be made for the increased moments. These mo- ments shall be assumed to be ten (10) per cent, greater than the moments in the interior panels. If wall columns are used they* shall be calculated to 1 carry one-half ( — ) the panel load plus any other 2 loads and if necessary the column shall be designed 10 for eccentric loadings. The wall beams .shall be de- 1 signed to carry one-third ( — ) of the panel load plus 3 any other loads. The minimum width of wall beams of reinforced concrete shall be twelve inches and never 1 less than one-half ( — ) the depth of beam. 2 REINFORCED CONCRETE COLUMNS. Section 456. Reinforced concrete columns shall not exceed in length fifteen (15) times the least side or diameter and where such columns exceed twelve (12) times the least diameter or side, the allowable compression of the concrete shall be taken as five hundred (500) pounds multiplied by the least side or diameter of the column in inches and divided by the unsupported length in feet. For columns subject to eccentric loading or bend- ing of an indeterminate amount, the above stress shall be reduced at least twenty (20) per cent. When the bending stresses in a column can be definitely deter- mined, the combined bending and direct stress shall not exceed five hundred (500) pounds per square inch. Columns with longitudinal rods shall have at least one (1) square inch of steel in the total area, and not less than four (4) rods; and rods shall not be used of a less diameter than one-half (*4) inch. The area of the longitudinal rods shall not be less than one-half ( T / 2 ) of one per cent, of the required cross section area of the column and shall not exceed four (4) per cent, of the effective cross sectional area of the column. The longitudinal rods must be tied to- gether to resist outward flexure at intervals not greater than the least width or diameter of column. The steel hoops shall not be less than one-quarter (J4) inch diameter and spaced not more than twelve (12) inches apart. 11 SPIRAL REINFORCED COLUMNS. SECTION 457. Section 456 Modified. Where the reinforcement consists of vertical bars and spiral hooping, the con- crete shall not be stressed beyond six hundred and fifty (650) pounds per square inch, provided that the amount of vertical reinforcement be not less than the spiral reinforcement nor greater than five (5) per cent, of the area within the hooping; that the percent- age of spiral hooping be not less than one-half (} 4 ) of one per cent, and not to exceed one and one-half ( 1 / 4 ) per cent; that the pitch of the spiral be uni- form and not greater than one-eighth (} 4 ) of the diameter of the column nor greater than three (3) inches; that the spiral be secured to the verticals at every intersection to insure the maintaining of its form and position; that the verticals be spaced so that their distance apart, measured on the circumference,, be not greater than nine (9) inches or one-eighth (*/£) the circumference of the column within the hooping. In such columns, the action of the hooping may be con- 4 sidered equal to two and four-tenths (2 — ) times its 10 amount taken as vertical reinforcing. No part of the concrete outside of the hooping shall be considered as a part of the effective column section. STRUCTURAL STEEL COLUMNS ENCASED IN CONCRETE. Section 458. Where structural steel columns, in steel frame structures or structures in which the loads are transmitted directly to steel column, are encased in concrete, the structural steel shall be proportioned to 15 carry the total dead load and fifteen-sixteenths ( — ) of 16 the total live load that can be transmitted to same and the concrete shall be proportioned to carrv one-six- 1 teenth ( — ) of the live load only; and in no case shall 16 12 the unit stress in the structural steel exceed sixteen thousand (16,000) pounds per square inch of net steel section, or shall the unit stress in the concrete exceed five hundred (500) pounds per square inch of net con- crete section. In columns of this design the concrete shall be rein- forced with spiral hooping of not less than one-half (J4) of one (1) per cent. The pitch of the spiral shall be uniform and not 1 greater than one-tenth ( — ) of the diameter of the 10 hooping nor greater than three (3) inches. The spirals shall be secured at each intersection in such a manner as to insure the maintaining of its form and position. No part of the concrete outside of the hooping shall be considered as a part of the effective column sec- tion. In latticed or open web structural columns it shall not be necessary to use the hooping specified above. In buildings with columns of this design the height shall be limited to sixteen stories or two hundred (200) feet in height, provided that the other require- ments of this Code for buildings of this height are com- plied with. All structural steel which is to be encased in con- crete shall be wrapped with wire in such a manner as to insure the bonding of the concrete to the steel and no structural steel which is to be encased in concrete shall be painted or oiled. Before encasing structural steel in concrete, scale or rust of any appreciable amount shall be removed. COLUMN SPLICES. Section 459. In all buildings hereafter to be erected the column splices shall be made in such a manner as to transmit the stresses for which they are designed. The connections shall be made by turnbuckle, sleeve nut, slip sleeve or by lapping the rods and bolting together in such a manner that the stresses will be 13 transmitted properly. If the device used requires the rod to be threaded the effective area shall be taken at the root of the thread. If a slip sleeve is used the rods must have their ends milled or equal. The dia- meter of the sleeve to be not over one sixteenth 1 (— ) inch larger than the diameter of the rod. Where 16 the bearing is made metal to metal the contact shall be made so as to transmit all stresses properly. Where the rods are in tension due to wind stresses, the con- nection shall be made by means of a positive connec- tion. The use of pipe sleeve connections is prohibited unless they fit the rods as above described. All column steel shall set directly in line with the steel below and must be constructed in such a manner as to eliminate any short bends in the steel. The steel reinforcement shall be spliced at such a point above the floor that the bond stress in the rod is developed enough to carry the increased load transmitted to it. CURTAIN WALLS IN SKELETON CONSTRUC- TION BUILDINGS. Section 460. Buildings having a complete skeleton construction of steel or of reinforced concrete con- struction, or a combination of both, may have exterior walls of reinforced concrete eight inches thick, pro- vided, however, that such walls shall support only their own weight and that such walls shall have steel reinforcement of not less than three-tenths (.3) of one per cent, in each direction vertically and horizon- tally, the rods spaced not more than twelve (12) inch centers and wired to each other at each intersection. All bars shall be lapped for a length sufficient to develop their full stress for the allowable unit stress for adhesion. Additional bars shall be set around openings, the verticals wired to the nearest horizontal bars, and the horizontal bars at top and bottom of openings shall be wired to the nearest vertical bars. The steel rods shall be combined with the concrete and placed where the combination will develop the 14 greatest strength, and the rods shall be staggered or placed and secured so as to resist a pressure of thirty (30) pounds per square foot, either from the exterior or from the interior on each and every square foot of each wall panel. MINIMUM THICKNESS OF SLABS. Section 461. Reinforced concrete slabs shall not be less than four (4) inches thick for floors and three {3) inches for roofs. FIREPROOFING. Section 462. For the purpose of fire protection the outer surface of reinforcing steel shall be kept away from the surface of the concrete. Two (2) inches in columns and girders. One and one-half (1J4) inches in beams. Three-quarters ($ 4 ) inch in slabs. No reinforcing steel not protected from fire shall be considered as adding to the strength of the con- struction. Lime or hard wall plaster shall not be considered as a fireproofing material in reinforced concrete work. SYSTEM. Section 463. No system of reinforced concrete shall be used which is not capable of design and in- vestigation in accordance with the formula and prin- ciples laid down in this Code. PROPORTION FOR MIXING REINFORCED CONCRETE. Section 464. All reinforced concrete shall be mixed in the proportion of (1) one part Portland Cement to (2) two parts clean, sharp sand and not more than (4) four parts aggregate. Where slag or other similar ma- terial is used, the proportion of aggregate shall be re- duced in order to have the voids properly filled. In no case shall more than two (2) parts sand be used to one (1) part cement and all mixng shall be done by machine, except where limited quantities are re- quired or where the conditions of the work make hand 15 mixing preferable ; hand mixing to be done only when approved by the Department of Buildings. In all mix- ing the separate ingredients shall be measured and shall be thoroughly mixed and must be uniform in color, appearance and consistency before placing. CEMENT, SAND AND INERTS. Section 465. (a) CEMENT. Only Portland Cement shall be used which conforms to the Standard Specifications of the American Society for Testing Materials. All cement shall be tested in lots of not more than one (1) car load, and the Department of Buildings may at any time demand that certified copies of all test records be submitted for examination. The minimum requirements for tensile strength for briquettes one (1) inch square in section shall be: NEAT CEMENT. 24 Hours in moist air 175 lbs. 7 Days (one day in air, six in water) 500 lbs. 28 Days (one day in air, twenty-seven in water) 600 lbs. ONE PART CEMENT, THREE PARTS STANDARD SAND. 7 Days (one day in air) 200 lbs. 28 Days (one day in air, twenty-seven in water) 275 lbs. SAND. (b) The sand used shall be clean, coarse, sharp, natural sand, preferably a mixture, of coarse and fine grains with the coarse grains predominating. The maximum percentage of clay or loam shall not exceed five (5) per cent, and at least sixty (60) per cent shall be retained on a fifty (50) mesh sieve and the sand shall contain at least ninety (90) per cent silica. AGGREGATE. (c) The aggregate shall consist of hard broken stone, free from dust, clean gravel, slag or similar material crushed and screened to pass a one (1) inch ring and rejected on a one-quarter (J^) inch ring. Both sand and aggregate shall be subject to the ap- 16 proval of the Department of Buildings, which may demand that any material in question be tested at the expense of the owner or owners, in an approved test- ing laboratory and the certified results submitted to the Department of Buildings to aid in forming an m opinion as to the fitness or unfitness of the material for the purpose intended. STEEL IN CONCRETE. * * Section 466. All steel shall be tested by an ap- proved testing laboratory and the Department of Buildings may, at any time, demand that certified copies of all test records be submitted to it for exam- ination. All steel used for reinforcing purposes shall comply with the “Standard Specifications” Governing the Chemical and Physical Properties of Concrete Re- inforcing Bars as adopted by the Association of American Steel Manufacturers, 1910. “The above modified — All reinforcing steel not rolled from billets shall be rolled from standard section Tee rails, and shall comply with the physical tests specified in Paragraph 2 of the above mentioned Standard Specifications. A complete physical test shall be made, by an approved testing laboratory, of each size of bar to be applied by the manufacturer on the contract from each ten (10) ton lot or less. These tests and materials shall be subject to the regulations prescribed in Paragraphs 2, 4, 5a, 6d, 7, 7e, 7f, 9 and 10 of the above mentioned specifications. Hot twisted bars of high carbon steel, shall be twisted with one complete twist in a length equal to not more than twelve (12) times the thickness of the bar. The Department of Buildings may demand the owner, builder, contractor, sub-contractor or foreman to make, or cause to be made, bending tests in the field, on all grades of reinforcing steel, when in their opinion there is any doubt as to whether the reinforc- ing steel is up to the standard of these regulations. These bending tests shall be those specified in the, above mentioned “Standard Specifications.” 17 PLACING CONCRETE AND STEEL. Section 467, In filling in concrete around reinforc- ing steel, the concrete must be worked continuously with suitable tools, as it is put in place. Filling the columns completely and puddling afterwards will not be permitted. In placing the concrete the work shall be so laid out that partially set concrete will not be subjected to shocks from the wheeling or handling ma- terial over it. Concrete placed in warm weather shall be drenched with water twice daily, Sunday included, during the first week after being put in place. When it is not possible to cast an entire structure in one operation, the work should be stopped ; for col- umns at the underside of girders for girders at a point midway between supports, unless a beam should occur at this point, in which case the joint should be offset a distance equal to twice the width of the beam; for slabs at the center of the span. When work is resumed the concrete previously placed shall be cleared of all foreign material, drenched and slushed with a mortar composed of one (1) part cement and one (1) part sand. Beams and girders shall not be constructed over freshly placed columns without permitting a period of ten (10) hours to elapse to provide for settlement of shrinkage in columns. Before resuming work the top of the column shall be cleansed of foreign matter, and if the column has become hard, the top shall be wet and slushed with the cement grout above specified. When beams are designed as tee beams, the slab shall be poured at the same time as the web. Some means satisfactory to the Department of Buildings shall be used to hold the reinforcing steel in its proper position by means of a spacing and clamping device. The longitudinal steel in beams and girders shall be so disposed that there shall be a thickness of concrete between the separate pieces of steel of not less than one and one-half (1J4) times the maximum sectional dimensions of the steel. 18 When steel is used in the compressive side of beams and girders, the rods shall be tied in accordance with requirements of vertical reinforced columns, with stir- rups connecting with the tension rods of the beams or girders. FREEZING WEATHER. Section 468. When concrete is placed in freezing weather, the materials must be heated and such pro- * visions made that the concrete can be put in place with- out freezing. The use of frozen lumpy sand or aggregate depend- ing on hot water used in mixing to thaw it out, will not be permitted. All reinforced concrete shall be kept at a temperature above freezing for at least forty-eight (48) hours after being put in place. All forms under concrete placed in freezing weather shall remain until all evidences of frost are removed from the concrete and the natural hardening of the concrete has pro- ceeded to the point of safety. All such work after centering is removed shall be given the physical test prescribed in Section 470. CENTERING AND FORMS. Section 469. All forms shall be built in a substantial manner, plumb and true, with tight joints, so that no appreciable part of the concrete mixture can escape, and shall be so supported and braced that they will carry all the usual loads which may come upon them without springing or deflection. An opening shall be left at the bottom of all column forms for cleaning and adjusting the steel. This opening shall not be closed until all is in readiness for pouring the columns. The forms shall be carefully cleaned just before concreting, and all chips, ice and other foreign matter removed. Before removing the shores under any beam or girder the columns supporting it shall be stripped, so that the columns may be examined on all sides. Pour- ing columns in chases left in the masonry shall not be allowed. Provided ample shores are used to carry the full 19 weight of the floor, column forms may be removed in not less than four (4) days after pouring. The time which shall elapse before removing the shores under beams and girders varies with the design and condition of the weather, but in no case shall they be removed in less than three (3) weeks after pouring, provided that the beams and girders carry their own weight only. Where beams and girders carry construc- tion loads from above, sufficient shoring shall be left in place to carry these loads until the completion of the work. The supports under floor slabs shall not be removed in less than ten (10) days after pouring, but this clause is not intended to prevent removing the joists and lag- ging in less time, provided the slabs are kept properly shored. INSPECTION AND TESTS. Section 470. When any reinforced concrete is used in construction, the owner shall provide for the in- spection of cement and inerts, as required by the In- spector of Buildings. Unless otherwise authorized in writing by the Inspector of Buildings, the owner shall also provide a special inspector of the work who shall be satisfactory at all times to the Inspector of Build- ings, and who shall be on the work continually during the mixing and the placing of concrete and steel and the removal of forms. Such special inspector shall make daily written reports to the Inspector of Buildings on the progress of the work. Before reinforced concrete work is started, the owner shall name in writing the special inspector, and such special inspector shall pass such examination as may be required by the Inspector of Buildings to de- termine his competency. Before a building containing reinforced concrete floors is occupied, the floors shall be tested by applying a load equal to two and one-half (2*4) times the figured live load to such parts as the Inspector of Buildings or deputies may select. The floor shall sus- tain this load for at least twenty-four (24) hours, 20 without cracking or other evident signs of failure. CONCRETE BLOCK CONSTRUCTION. Section 471. (a). Concrete building blocks may be used for building three (3) stories or less in height, where such blocks have passed the test hereinafter specified. Concrete shall be composed of at least one (1) part . Portland cement and not more than three (3) parts w sand, and not to exceed five (5) parts crushed rock or gravel. The cement, sand and aggregate shall comply with the requirements specified in Section 465 for these ma- terials. In no case shall the walls or webs of the blocks be less in thickness than one-quarter (%) of the height. The hollow space in any block shall not exceed thirty-five (35) per cent. (b) The thickness of walls for any building when concrete blocks are used shall be the same as the thick- ness of a brick wall, except where the allowable crush- ing strength of such wall is exceeded; then the thick- ness must be increased. An eight (8) inch block shall be considered one (1) brick thick in wall measure- ments. Where the face of a building is of concrete building block and the backing is of brick the facing of con- crete blocks must be well bonded to the brick, with headers projecting four (4) inches into the brick work, every fourth course being a header course. All walls where blocks are used shall be laid with Portland cement mortar. (c) All concrete blocks before being used in con- struction in buildings shall have obtained the age of at least four (4) weeks. Such blocks shall develop a crushing strength of fifteen hundred (1,500) pounds per square inch at twenty-eight (28) days. Where girders, beams or joists rest on the walls so that the end reaction exceeds four thousand (4,000) * pounds the blocks below such concentrated loads must be made solid a distance below and to the side, as may ~ be required by the Department of Buildings. 21 Concrete sills and lintels spanning over four (4) feet six (6) inches shall be reinforced and the ends rest on solid blocks or solid walls. TEST OF CONCRETE BLOCKS. Section 472. All concrete materials made of Port- land cement, sand and crushed rock or gravel, or ce- ment and sand, which are larger than the standard brick size and which are molded and then set in place in the structure, shall come under the provisions as follows : (a) APPLICATION FOR TESTS: Before any concrete block is used in a building an application for its use and for a test of the same shall be filed with the Department of Buildings. A description of the ma- terials and the manufacture of same shall be filed with the application. (b) TESTS TO BE MADE : The concrete blocks shall be subject to the following tests: Compression, transverse and absorption. All such tests shall be made in some laboratory of recognized standing under the supervision of a repre- sentative from the Department of Buildings. The tests shall be made at the expense of the owner. (c) For the purpose of these tests at least ten (10) samples of test pieces shall be provided. Such samples shall be selected from stock by a representative from the Department of Buildings, or may be made in the presence of such representative. The samples shall be of the regular size as used in construction, except that when the samples are too large to use in the ordinary testing machines, in which case smaller sized blocks shall be made for testing under the direction of a rep- resentative from the Department of Buildings. (d) Tests shall be made in series of at least three (3), composed of four (4) samples each. The trans- verse test shall be made on full size samples. Half size samples may be used for the crushing test, and the re- maining samples are to be kept in reserve in case ex- ceptionally high values are shown by these tests which may make it necessary to discard certain of them. All 22 samples must be marked for identification and com- parison. The weight of the material in the block per cubic foot shall be determined. (e) TRANSVERSE TEST. The transverse test shall be made as follows : The samples shall be placed flatwise on two (2) rounded knife-edge bearings set parallel and seven (7) inches apart. A load is then ap- plied on top of the test piece midway between the sup- ports, and transmitted through a similar rounded knife- edge until the rupture of the sample.- The modulus of rupture shall be determined by multiplying the total breaking load in pounds by twenty-one (21) minus [three (3) times the distance between the supports in inches] and then dividing the result thus obtained by twice the product of the width in inches by the square of the depth in inches. Allowance shall be made in figuring the modulus of rupture for the hollow spaces in the test piece. 3 WL Modulus of rupture R = 2 B 2 (f) TEIE COMPRESSION TEST. The com- pression test shall be made as follows : Samples shall be cut in blocks in such a manner as to contain the full web section. The samples must be carefully measured, then bedded flatwise in plaster of Paris to secure uniform bearing in the testing machine, and then crushed. The total breaking load is then divided by the area of square inches in compression. Deduc- tion is to be made for hollow spaces. (g) ABSORPTION TEST. The absorption test must be made as follows : The block is first to be thoroughly dried and weighed. It is then to be placed in water of a depth of one-half (^4) inch face down- ward. After being in the water for thirty (30) minutes, the block is again weighed, then immersed in water for four (4) hours and weighed again. It is then immersed for forty-eight (48) hours and the result noted. After weight is taken the compressive strength of the block while still wet is determined as provided above. REQUIREMENTS AND CONDITION OF AP- PROVAL— REVOCAL OF LICENSE. Section 473. (a) The following requirements must be complied with in order to secure an acceptance of the material : The modulus of rupture for concrete blocks at (28) twenty-eight days old shall average one hundred and fifty (150) and must not fall below one hundred (100) in any case. The ultimate compressive strength at twenty-eight (28) days must average fifteen hundred (1500) pounds per square inch and must not fall below seven hundred (700) in any case. The percentage of absorption (being the weight of water absorbed divided by the weight of the dry sample) must not average higher than seven (7) per cent and must not exceed ten (10) per cent in any case. The reduction of compressive strength must not be more than thirty-three and one-third (33 1-3) per cent except that when the lower figure is still above one thousand (1000) pounds per square inch, the loss in strength may be neglected. (b) The approval of any material is given only under the following conditions : A plant for the production of the material must be in full operation when the official tests are made. The names of the firms or corporations and the re- sponsible officers must be placed on file with the De- partment of Buildings and changes in same promptly reported. The Department of Buildings may require full tests to be repeated on samples selected from the open mar- ket, when in their opinion there is any doubt as to whether the product is up to the standard of these regulations, and the manufacturer must submit to the Department of Building once in at least every four months a certificate of tests showing that the average resistance of three specimens to cross breaking and crushing are not below the requirements of these regu- lations. Such tests must be made by some laboratory of recognized standing, on samples selected either by the Department of Buildings, or the laboratory from materials actually going into construction, and not ones furnished by the manufacturer. In case the results made under the preceding divisions show that the standard of these regulations is not maintained, the approval of the Department of Buildings to the manu- facturer of said blocks shall be at once suspended and revoked. No certificate of approval shall be considered in force more than four (4) months, unless there be filed with the Department of Buildings at least every four (4) months following, a certificate from some reliable physical testing laboratory, showing that the average of the three (3) specimens tested for compression and three (3) specimens tested for transverse strength comply with the requirements of the Building Depart- ment. Manufacturer and user of any such concrete blocks as are mentioned in this regulation, or either of them, shall at any and all times, have made such test of cement used in making such blocks, or such further tests of the completed blocks, or each of them, at his own expense and under the supervision of the De- partment of Buildings as may be required. (c) A license shall be granted to those intending to manufacture concrete blocks, said license to be re- voked for the following causes : 25 3 0112 077859988 Willful violation of speculations, laws and or] nances. Dishonest methods. Use of improper materials. Section 2. That Title X, Concrete Constructi