TABLE 9.4 ASTM Standard Rebars Bar size no.a Nominal dimensionsb Diameter mm [in.] Cross-sectional area, mm2 [in.2] Weight kg/m [lbs / ft] a Equivalent inch-pound bar sizes are the designations enclosed within brackets. b The equivalent nominal dimensions of inch-pound bars are the values enclosed within brackets. TABLE 9.5 Rebar Sizes and Grades Conforming to ASTM Specifications Type of steel and ASTM specification Bar size numbers Grade* Billet steel Low-alloy steel *Minimum yield strength. Table 9.5 shows the bar sizes and strength grades covered by ASTM Specifications A615/A615M and A706/A706M.* The grade number indicates minimum yield strength, MPa [ksi] of the steel. Grade 420 [60] billet-steel rebars, conforming to ASTM A615/A615M, are currently the most widely used type. Low-alloy steel rebars conforming to the ASTM A706/A706M Specification are intended for applications where controlled tensile properties are essential, for ex- *Many of the ASTM specifications for steel reinforcement are in a dual units formatmetric units and inch-pound units. The designations of such specifications are also in a dual format, e.g., A615/A615M. The metric units in the specification apply when A615M is specified. Similarly, inch-pound units apply under Since rail-steel and axle steel reinforcing bars (ASTM A996/A996M) are not generally available except in a few areas of the country, these types of bars are not discussed herein. Should the need arise to evaluate or specify rail-steel or axle-steel bars, ASTM Specification A996/A996M should be reviewed. ample, in earthquake-resistant design and construction. The A706/A706M Specification also includes requirements to enhance ductility and bendability. Rebars conforming to A706/A706M are also intended for welding. Weldability is accomplished by the specifications limits or controls on the chemical composition of the steel. Welding of rebars should conform to the requirements of StructuralWelding CodeReinforcing Steel, ANSI/AWS D1.4. Billet-steel rebars conforming to ASTM A615/A615M are not produced to meet weldability requirements. They may be welded, however, by complying with the requirements in ANSI/AWS D1.4. Coated rebars, either epoxy-coated or zinc-coated (galvanized), are used where corrosion protection is desired in reinforced concrete structures. The ACI 318 Building Code requires epoxy-coated rebars to conform to ASTM Specifications A775/ A775M or A934/A934M. Zinc-coated (galvanized) rebars are required to conform to ASTM A767/A767M. ASTM Specification A955M for stainless steel rebars was published in 1996. Stainless steel rebars are intended for use in highly-corrosive environments, or in buildings which require non-magnetic steel reinforcement. In 1997, ASTM issued Specification A970/A970M for headed reinforcing bars. A headed rebar consists of a head fastened or connected to one or both ends of a rebar. The head, which can be a rectangular or round steel plate, is connected to the rebar by welding or threading. Another type of headed rebar has an integrallyforged head. The purpose of the head is to provide end anchorage of the rebar in concrete. Headed rebars can be used advantageously in lieu of bars with standard end hooks thereby relieving congestion of reinforcement and enhancing constructability. Welded-wire fabric is an orthogonal grid made with two kinds of cold-drawn wire: plain or deformed. The wires can be spaced in each direction of the grid as desired, but for buildings, usually at 12 in maximum. Sizes of wires available in each type, with standard and former designations, are shown in Table 9.6. Welded-wire fabric usually is designated WWF on drawings. Sizes of WWF are designated by spacing followed by wire sizes; for example, WWF 6  12, W12/ W8, which indicates plain wires, size W12, spaced at 6 in, and size W8, spaced at 12 in. WWF 6  12, D-12/D-8 indicated deformed wires of the same nominal size

Electrolytic action between aluminum and less active metals should be avoided, because the aluminum then becomes anodic. If aluminum must be in touch with other metals, the faying surfaces should be insulated by painting with asphaltic or similar paints, or by gasketing. Steel rivets and bolts, for example, should be insulated. Drainage from copper-alloy surfaces onto aluminum must be avoided. Frequently, steel surfaces can be galvanized or cadmium-coated where contact is expected with aluminum. The zinc or cadmium coating is anodic to the aluminum and helps to protect it. Aluminum Standards and Data, Engineering Data for Aluminum Structures, Designation Systems for Aluminum Finishes, and Specifications for Aluminum Structures, The Aluminum Association, Washington, D.C. E. H. Gaylord, Jr., and C. N. Gaylord, Structural Engineering Handbook, 3rd ed., McGraw-Hill Publishing Company, New York. Copper and its alloys are widely used in the building industry for a large variety of purposes, particularly applications requiring corrosion resistance, high electrical conductivity, strength, ductility, impact resistance, fatigue resistance, or other special characteristics possessed by copper or its alloys. Some of the special characteristics of importance to building are ability to be formed into complex shapes, appearance, and high thermal conductivity, although many of the alloys have low thermal conductivity and low electrical conductivity as compared with the pure

Open expansion joints are sometimes used for interior locations where the opening is not objectionable. When exposed to water from above, as in parking decks, open joints may be provided with a gutter below to drain away water. The engineer should show all necessary vertical and horizontal joints on design drawings. All pertinent details affecting reinforcement, water stops, and sealers should also be shown. Construction joints should be designed and located if possible at sections of minimum shear. These sections will usually be at the center of beams and slabs, where the bending moment is highest. They should be located where it is most convenient to stop work. The construction joint is often keyed for shearing strength. If it is not possible to concrete an entire floor in one operation, vertical joints preferably should be located in the center of a span. Horizontal joints are usually provided between columns and floor; columns are concreted first, then the entire floor system. FIGURE 9.9 Types of construction joints. Circled numbers indicate order of casting. Various types of construction joints are shown in Fig. 9.9. The numbers on each section refer to the sequence of