Course Script
Welded Wire Reinforcement Use in Concrete Structures
Slide 1: Welcome
Thank you for your interest in Welded Wire Reinforcement Use in Concrete Structures. Concrete structures are being successfully and economically reinforced with high-strength, uniformly distributed welded wire reinforcement (WWR).
Welded wire reinforcement can be used in virtually any structural application: buildings and bridges, highways and tunnels, and pipelines and precast component systems.
Using welded wire reinforcement in concrete controls cracks, improves performance of concrete work, and reduces the need for joints in slabs, thus permitting longer panels. This engineered product, reduces construction costs, speeds construction, and creates more durable structures.
Slide 2: AIA Required Best Practice
The Wire Reinforcement Institute (WRI) sponsors this program provided by Hanley Wood, a Registered Provider with the American Institute of Architects Continuing Education Systems (AIA/CES).
This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing or dealing in any material or product.
Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of completion for both AIA members and non-AIA members are available to print for self-reporting and record-keeping needs.
Questions related to specific materials, methods and services should be directed to the Wire Reinforcement Institute upon completion of this course.
Slide 3: Copyright Materials
This presentation is protected by U.S. and international copyright laws. Reproduction, distribution, display and use of this presentation without the written permission of the Wire Reinforcement Institute is prohibited.
Slide 4: Course Description
The construction industry has long relied on welded wire reinforcement’s strength and flexibility, especially in applications that might be subjected to high flexure and shear stresses.
In the early 1900s, welded wire reinforcement, then known as wire fabric, tested well in cinder concrete construction and in short-span cinder concrete arch construction. It subsequently was used in the construction of Grand Central Terminal and the Empire State Building in New York City, and the Chicago Tribune Towers in Chicago, among other notable projects.
Recent advances in welded wire reinforcement technology have produced ever-increasing wire diameters and materials that can be welded together, enabling the product to be used in different structural components.
This course begins by covering the standards governing the manufacture of welded wire reinforcement and how it’s specified for job orders.
We will then review the design basics of the wires used in reinforcement, such as spacings, sizes, lengths, widths, and overhangs, and how the product is produced and tested for mechanical properties, such as tensile, reduction of area, bend, and weld shear strength. We’ll conclude with examples of how welded wire reinforcement is used in a wide array of structural applications.
At the end of the course there will be a quiz. You’ll have to pass the quiz to earn credit for the course and to print or save a Certificate of Completion.
Slide 5: Learning Objectives
At the end of this course, you will be able to:
· Explain the value engineering of using welded wire reinforcement
· List the design basics of welded wire reinforcement
· Define how welded wire reinforcement is manufactured
· Identify applications and design examples
SECTION 1: INTRODUCTION
Slide 6
An increasing number of contractors are using welded wire reinforcement because of its labor cost savings. The manufacturing process helps to facilitate off-site fabrication and on-site installation. By being machine produced, welded wire reinforcement requires less assembly and setup time, reduces inspection time, and allows for tighter clearances and tolerances, resulting in overall project cost savings.
Slide 7
High-strength welded wire reinforcement can be uniformly or variably spaced to successfully and economically reinforce concrete structures. The wide variety of available wire sizes and spacings make it possible to provide accurate cross-sectional areas of steel for reinforcement. The welded cross wires properly position and uniformly space the reinforcement for uniform stress distribution and effective crack control.
Slide 8
The higher strength capacities to which welded wire reinforcement can be produced means less material is needed to achieve equivalent capacities, thus reducing overall construction costs. Fewer foremen or inspectors are needed to track the project, thus less supervision is needed, reducing overhead costs. Accelerated pour times, construction schedules, and project completion result in overall lower in-place final costs.
Slide 9
Standards governing the manufacture of welded wire reinforcement are American Society of Testing and Materials (ASTM) A1064, and the American Association of State Highway and Transportation Officials (AASHTO) M55 for plain wire reinforcement sheets, and AASHTO M221 for deformed wire sheets. Two codes governing the use of welded wire reinforcement are the American Concrete Institute (ACI) ACI-318 Building Code Requirements for Structural Concrete and the AASHTO LRFD Bridge Design Specifications or the AASHTO design handbook. Additional resources include the Wire Reinforcement Institute (WRI) WWR-500-Manual of Standard Practice for Welded Wire Reinforcement.
Slide 10
Welded wire reinforcement is usually specified according to a description of the scope of work, material code requirements, construction methods (shop drawings, fabrication, handling, storage and surface condition of reinforcement, placing and securing, splicing of reinforcement, substitutions, inspections), method of measurement, and basis of payment (reinforcement).
SECTION 2: DESIGN BASICS
Slide 11
This section will cover the design basics of welded wire reinforcement.
Slide 12 INTERACTION: Design Basics (TAB INTERACTION)
Click on the tab on the left to hear descriptions of the design basics of welded wire reinforcement.
Slide 12: Style
Style designates a complete unit of welded wire reinforcement. Style refers to the spacings and sizes as well as the length and width of the wires used in welded wire reinforcement.
A typical style designation for a unit of welded wire reinforcement is 6 x 12-W12 x W5, where:
· 6 inches (152mm) is the spacing of the longitudinal wire
· 12 inches (305 mm) is the spacing of the transverse wires
· W12 (0.12 square inch; 77mm2) is the size of the longitudinal wires and
· W5 (0.05 square inch; 32mm2) is the size of the transverse wires.
Metrically, this style would be expressed as 152 x 305-MW77 x MW32.
The terms longitudinal and transverse here refer to the manufacturing process and not to the relative position of the wires in a concrete structure.
Slide 12: Wire Size Designation
Wire size designation of plain and deformed individual wire is based on the cross-sectional area of a given wire.
The cross-sectional steel area is the basic element used in specifying the required wire size. The prefixes W (plain) and D (deformed) are used in combination with a number. The number following the letter gives the cross-sectional area in hundredths of a square inch. Thus W4 would indicate a plain wire with a cross-sectional area of 0.04 square inches and a D10 wire would indicate a deformed wire with a cross-sectional area of 0.10 square inches.
Once the cross-sectional area of a wire and the space is known, the total cross-section area per foot of width can be determined: a W6 wire on 4-inch centers would provide 3 wires per foot with a total cross-section area of 0.18 square inch per foot of width.
A welded deformed wire style would be noted the same way except for the substitution of the prefix D for W.
When describing metric wire, the prefix M is added: MW for metric plain wire and MD for metric deformed wire. The wire spacings in metric welded wire reinforcement are given in millimeters (mm), and the cross-sectional areas of the wires in square millimeters (mm2).
Slide 12: Dimensions
Dimensions refer to the description of width, length, and overhang dimensions of sheets.
Slide 12: Width
Width is the center-to-center distance between outside longitudinal wires. This dimension does not include overhangs.
Slide 12: Side Overhang
Side overhang is the extension of transverse wires beyond the centerline of outside longitudinal wires. If no side overhang is specified, welded wire reinforcement is furnished with overhangs on each side, of no greater than 1 inch (25 mm). Wires can be cut flush (no overhangs) specified as +0 inch, +0 inch. When specific overhangs are required, they are noted as +1 inch, +3 inch or +6 inch, +6 inch, indicating the overhang on either side of the sheet.
Slide 12: Overall Width
Overall width is the width including side overhangs in inches (or mm), in other words, the tip-to-tip dimension of transverse wires.
Slide 12: Length
Length is the tip-to-tip dimension of longitudinal wires. Whenever possible this dimension should be an even multiple of the transverse wire spacing. The length dimension always includes end overhangs.
Slide 12: End Overhangs
End overhangs are the extension of longitudinal wires beyond the centerline of outside transverse wires. Unless otherwise noted, standard end overhangs are assumed to be required and end overhangs need not be specified. Non-standard end overhangs may be specified for special situations; preferably, the sum of the two end overhangs should equal the transverse wire spacing.
Slide 12: Splicing.
Unless otherwise specified, welded wire reinforcement is spliced either end-to-end or side-to side.
Adjacent sections are spliced end-to-end (longitudinal lap) by overlapping a minimum of one full spacing plus 2 inches plus the length of the two end overhangs. The splice length is measured from the end of the longitudinal wires in one sheet to the end of the longitudinal wire in the lapped piece of sheet.
Adjacent sections are spliced side-to-side (transverse lap) a minimum of one full spacing plus 2 inches. The splice length is measured from the centerline of the first longitudinal wire in one sheet to the centerline of the first longitudinal wire in the lapped sheet.
Finger lapping is a term used to indicate the development and splice lengths of wire. Deformed wire can be spliced according to the provisions of the ACI code for splice lengths.
Slide 13
The yield strength values shown in Table 1 are ASTM’s requirements for minimum yield strength measured at a strain of 0.005in/in. The American Concrete Institute’s 318 Building Code states that yield strength values greater than 60,000 pounds per square inch (psi) may be used, provided they are measured at a strain of 0.0035 in/in. Higher-yield strength welded wire is available and can be specified in accordance with ACI code requirements.
Slide 14
Elongation test criteria on maximum strength (or maximum stretch) is shown in tables 1(b) and 1(c). Maximum stretch can be defined as total elongation, which is a test in ASTM A370, A4.4.2, measuring both the elastic and plastic extension. The testing recorded in Tables 1(b) and 1(c) correlates with other testing and research done by some major universities, which found that high-strength welded wire reinforcement is capable of developing significant strains and exhibits sufficient ductility to redistribute the strains to avoid brittle shear failure.
Slide 15
The values shown in Table 1 are the ASTM requirements for weld shear strength, which contribute to the bond and anchorage of the wire reinforcement in concrete. A maximum size differential of wires being welded together is maintained to assure adequate weld shear strength. For both plain and deformed wires, the smaller wire must have an area of 40 percent or more of the steel area of the larger wire.
Slide 16
Welded wire reinforcement can be bent many times and most springs are made of a wire type product.
SECTION 3: PRODUCTION
Slide 17
In this next section we will discuss how welded wire reinforcement is produced and tested for mechanical properties.
Slide 18
Wire is manufactured from rod material. Rods are cold drawn or cold rolled through a series of dies or rolls to reduce the diameter and increase the yield and tensile strengths of the steel wire. Welded wire reinforcement is then fabricated from the cold-worked or cold drawn wire by electrical resistance welding. On machines, longitudinal wires are set and spaced as required by the job order, and the transverse wires or cross wires are fed via another part of the machine. The electrical resistance welding process is completed by machine and stepped at intervals as required by the job order. This step of the process is how the transverse wire spacings are set. Each wire intersection is electrically resistance-welded by an automatic welder. Wires are fused into homogeneous sections, thereby ensuring permanency of spacing and alignment in either direction. Welded wire reinforcement is fabricated with all deformed wire, all smooth or non-deformed wire, or a combination of deformed and smooth or non-deformed wires.
Slide 19
Welded wire reinforcement for construction is usually manufactured in 5- to 8-foot -wide rolls, with 5-foot-wide rolls most common. Sheets (or styles) are produced in varying widths and lengths with typical widths of 5 to 8 feet produced. Sheets 12 feet wide and larger are produced primarily for highway paving and precast components. Sheets can be provided up to 40 feet or more in length, but 12-,15-, 20-, and 25-foot lengths are common.
Smaller custom orders can be manufactured. Additionally, welded sheets can be produced using wire sizes up to D31 (equivalent to a #5 rebar), enabling it to be used in more heavily reinforced products.
Slide 20
Welded wire reinforcement is subject to certain mechanical property requirements according to ASTM standards. Tensile tests, reduction of area, bend tests, and weld shear strength tests are normally done at the time the wire is drawn and after the welded wire reinforcement is fabricated. The finished product must satisfy the mechanical properties when tested after fabrication.
Tensile tests are made on wire cut from the welded wire reinforcement and tested either across or between the welds. Reduction of area (the ability of the steel wires to withstand large strains and redistribute stress) is measured at the ruptured section of the tensile specimen. The bend test is performed on a specimen taken from between the welds. The weld shear strength test is taken at longitudinal and transverse wire weld intersections. As the welds in welded wire reinforcement contribute to the bonding and anchorage value of the wires in concrete, the weld acceptance tests must be made in a jig that will stress the weld in a manner similar to which it is stressed in concrete.