CODE FOR FUSION WELDING AND GAS CUTTING IN BUILDING CONSTRUCTION
Formulated by American Welding Society Committee on Building Codes
PART A - Structural Steel
Section 1. General Application
1. Fusion welding may be substituted for or used in combination with the riveting, bolting or other requirements already prescribed in the building code of the City of _____________, hereinafter called the "Building Code," for connecting together, or assembling the component parts of, steel beams, girders, lintels, trusses, columns and other structural steel used in building construction; provided that the welding be done in accordance with Sections 3 to 7, inclusive, or this code.
2. Gas cutting may be substituted for shearing or sawing in the fabrication of structural steel members or parts, used in building construction, provided the cutting be done in accordance with Section 8 of this code.
Section 2. Definitions
The definitions of welding terms, as approved and published by the American Welding Society, shall govern for any welding terms appearing in this code.
For convenience, some of the more common terms have been included herein, and their specific applications under this code are defined as follows:
1. Fusion Welding. -
The process of joining metal parts in the molten, or molten and vapor states,
without the application of mechanical pressure or blows.
Under this code, fusion welding is restricted to the arc and gas welding processes.
2. Root. - The zone at the bottom of the cross-sectional space provided to contain a fusion weld.
3. Throat. - The minimum thickness of a weld along a straight line passing through the root.
Under this code the throat of a fillet weld shall be the distance along a line from the spot to the hypotenuse at right angles thereto, of the largest isosceles right triangle that can be constructed in the cross-section of the fillet weld; and the throat of a butt weld shall be equal to the thickness of the thinner part joined.
4. Fillet Weld. - A weld of approximately triangular cross-section, whose throat lies in a plane disposed approximately 45 deg. with respect to the surfaces of the parts joined.
The size of a fillet weld shall be expressed in terms of the width in inches of its adjacent fused sides.
5. Butt Weld. - A weld whose throat lies in a plane disposed approximately 90 deg. with respect to the surfaces of at least one of the parts joined.
The size of the butt weld shall be expressed in terms of its net or unreinforced throat dimension in inches.
6. Weld Length. - The length of a weld shall be considered to be the unbroken length of the full cross-section of the weld exclusive of the length of any craters.
7. Weld Dimensions. - Under this code the dimensions of a weld shall be expressed in terms of its size and length.
8. Gas Cutting. - The process of severing ferrous metals by means of the chemical behavior or oxygen, in the presence of ferrous metals at high temperatures, to produce a kerf or cut of uniform width without burning the edges of the kerf or cut.
Section 3. Materials
1. The grade of structural steel to be used under this code shall be that already prescribed in the Building Code.
2. The electrodes, welding wire and welding rods, shall either be one of the grades specified by the American Bureau of Welding in its Bulletin No. 2, or some equally good grade which, in the hands of an experienced welder, shows good weldability in flat, vertical and overhead positions. In the discretion of the Superintendent of Buildings it may be required to show the strength specified in Paragraphs c and g, Section B, of the American Bureau of Welding Specifications.*
Section 4. Permissible Unit Stresses
1. Welded joints shall be proportioned so that the loads specified in the Building Code shall not cause stresses therein to exceed the following amounts in pounds per square inch:
Shear on section through throat of weld .................... 11,300
Tension of section through throat of weld ..................13,000
Compression on section through throat of weld ........15,000
Maximum fibre stresses due to bending shall not exceed the values prescribed above for tension and compression respectively.
2. In designing welded joints adequate provision shall be made for bending stresses due to eccentricity, if any, in the disposition or section of base metal parts.
Section 5. Design
1. The architect or engineer designing or supervising a welded structure shall be experienced and skilled in such work.
2. Plate Girders. - Girders shall be proportioned either by their moments of inertia or by the flange area method. In applying the flange area method to welded girders having no holes in the web, one-sixth of the web area may be considered a part of each flange area.
Stiffeners may be either angles or flat bars, welded to the top and bottom flanges, and to the web, by continuous or intermittent fillet welds designed to transmit the stresses.
Connection of component parts of flanges to each other and of flanges to web shall be by continuous or intermittent fillet welds designed to transmit the stress.
3. Beams. - The use of continuous beams and girders, designed in accordance with accepted engineering principles, shall be permitted provided that their welded connections be designed to transmit the stresses to which they may be subjected.
The connections at the ends of non-continuous beams shall be designed so as to avoid excessive secondary stresses due to bending.
4. Columns. - Fillet welds connecting the component parts of a built-up column may be either continuous or intermittent. If intermittent, the length of each weld at the ends of the column shall be equal to the least width of the column. The length of the intervening welds shall be not less than 1 1/2 inches, spaced not more than 4 inches in the clear. The size, length and spacing of the fillet welds shall be such as to provide the same strength, per unit of column length, as the rivets specified elsewhere in the Building Code.
Lattice bars and tie plates, if used, shall be welded so as to secure strengths equal to those of the rivets specified therefor elsewhere in the Building Code.
5. Butt Joints. - The edges of base metal parts, 1/4 inches or more in thickness, transmitting stress by means of butt welds shall be beveled. For single and double vee joints, the bevel of each part shall be not less than 30 deg., thus forming an open space with an angle of not less than 60 deg. For single and double bevel joints, the bevel shall be not less than 45 deg.
Before welding, the root edge or face of one part shall be separated from the root edge or face of the other part by the spacing given for butt joints on pages 22 to 28 inclusive, of Section E of American Bureau of Welding Specifications.*
All butt welds shall be reinforced by depositioning additional metal on the weld to a height extending beyond the surface of the thinnest part joined. The height of said reinforcement shall be not less than the following percentages of the thickness of the thinnest part joined: 20 percent for single vee and single bevel butt welds, and 12 1/2 percent, on each side, for double vee and double bevel butt welds.
Section 6. Workmanship
1. Contractors for welded structures shall be required to satisfy the Superintendent of Buildings as to their ability to produce satisfactory welded joints of the forms specified, and with the process (arc or gas), materials and equipment to be used on the proposed work.
2. The quality of welds permitted under this code shall conform to the practice recommended in Section D of the American Bureau of Welding Specifications.*
3. Surfaces to be welded shall be free from loose mill scale, rust, paint or other foreign matter. A thin coat of linseed oil or equivalent, over the surfaces to be welded, need not be removed. This provision applies both in the case of new structures and where new steel is to be welded to steel in an existing structure.
4. In assembling and during welding, the component parts of a built-up member shall be held by sufficient clamps, or other adequate means, to hold the parts in proper relation for welding.
Section 7. Erection
1. Structural steel parts shall not be painted before they are welded. Parts that are welded in the shop, to be erected by bolts or rivets, shall receive the usual painting after the shop welding is finished. Parts to be field welded shall receive a coat of linseed oil after shop work is completed, and after erection and field welding, they shall receive as many coats of paint as the total number specified elsewhere in the Building Code for shop and field painting.
2. For all welded structures over 30 ft. in height, erection bolts, or equivalent means shall be employed for temporarily supporting the members and for insuring proper alignment.
Section 8. Gas Cutting
1. The contractor shall be required to satisfy the Superintendent of Buildings as to his ability to produce satisfactory gas cuts.
2. Gas cut edges shall be smooth and regular in contour.
3. Gas cutting may be used in the preparation of gas metal parts for welding, provided the edges so cut are thoroughly cleaned after cutting so as to expose clean steel.
4. Gas cutting shall not be permitted to replace the milling of surfaces specified elsewhere in the Building Code.
5. Gas cutting shall not be permitted on any member while it is carrying stress. This restriction shall not apply to detail cutting for the correction of minor fabricating errors, where the removal of metal resulting from such gas cutting would not reduce the required strength of the member that is to be cut.
6. Gas cutting of holes in a member which has not been designed therefore shall not be permitted.
*Refers to Specifications for Test Specimens, Their Preparation and Testing,@ prepared by the Structural Steel Welding Committee of the American Bureau of Welding, the research department of the American Welding Society, 33 W. 39th Street, New York City.