"At the suggestion of Professor E. W. Carlton, Chairman, Civil Engineering Department, Missouri School of Mines and Metallurgy, the author selected as subject for research thesis, “A Comparative Determination of Weld Shear Values in Welded Wire Reinforcement Fabric”.
In 1948, the Wire Reinforcement Institute initiated a research program to measure the actual stresses, including weld shear stresses, that occur in Welded Wire Fabric when used as reinforcement in a concrete slab. A great majority of this research was under the supervision of Professor Carlton.
The results of these investigations indicated a wide variation in strength of welds. As a means of increasing the uniformity of welds and welding technique of wire fabric, a special weld tester was developed in 1950 by Professor A. V. Kilpatrick, Professor of Mechanical Engineering at the Missouri School of Mines and Metallurgy, and Professor E. W. Carlton. Prior to this time, no efficient, industry usuable, mechanical weld tester had been developed. The express purpose in designing the weld tester was to reproduce, mechanically, as nearly as possible, the actual shear stresses acting on Welded Wire Fabric embedded in concrete.
The results of the weld tester were of such importance that ASTM Specifications A185-37 for Welded Steel Wire Fabric (which required no weld test), were revised to A185-54T which state the following:
“Section 5(b) In order to assure adequate weld shear strength between longitudinal and transverse wires, weld shear test as described in Section 6(c) shall be made. The minimum average shear value of the welds for mesh, having a wire size differential of up to and including four gages, shall have a breaking strength in pounds of not less than 35,000 multiplied by the area of the longitudinal wire in square inches."
"Section 5(c) Fabric having a wire gage differential between longitudinal and transverse wires of five or greater shall not be subject to weld shear requirement."
Section 6(c) Weld shear tests for determination of conformance to the requirements of Section 5(b) shall be conducted using a fixture of such design as to prevent rotation of the transverse wire. The transverse wire shall be placed in the anvil of the testing device which is secured in the tensile machine and the load then applied to the longitudinal wire.”
In the design of the Carlton-Kilpatrick Weld Tester (a more complete description of the tester is included in the section pertaining to test equipment) are included anvils of various sizes corresponding to the various gages 14 through 4/O. The varying sizes of anvils were included in the design to insure a positive grip of the transverse wire, thus preventing its rotation. Also included with the weld tester is an additional anvil which is the No. 2 size anvil. This was the anvil used with the original tester design, later augmented by the complete set of anvils. Throughout the thesis, this additional anvil will be referred to as the “average” anvil, while the anvils belonging to the complete set will be called "design" anvils.
It came to the attention of Professor Carlton that it is common practice in certain areas of the Welded Wire Fabric Industry to use the average anvil for all sizes of transverse wire rather than the design size anvil.
The question arises as to whether, by so doing, the tester is violating section 6(c) of ASTM specifications, which state that, "tests shall be conducted using a fixture of such design as to prevent rotation of the transverse wire". That is, is rotation allowed by using the average, rather than the design, anvil? And, if so, is there a resulting error in the shear value assigned to the weld?
It is the purpose of the author to arrive at an answer to the above stated problem by means of comparative tests. The exact procedure will be outlined in a later section.
The importance of obtaining the correct value of weld shear resistance can be emphasized by outlining a few experimentally proven facts. They are as follows:
a) In any reinforced concrete structure, the reinforcing steel would serve no end unless it was adequately bonded to the concrete.
b) “The term bond as applied to smooth or deformed steel bars does not define the resistance to slipping of welded wire fabric reinforcement; anchorage is a better term, because it defines the functions of the transverse wires which are responsible for resisting slip.”
c) When subjected to pull out tests the longitudinal wires do not slip until the weld fails in shear.
d) The results of bond studies along the longitudinal wires showed unit bond stresses of about 200 psi, which is very low when compared to the ultimate strength of the wire.
The above outlined facts serve to prove that the bonding of Welded Wire Fabric is dependent upon the value of the weld in shear and that without proper bonding, the reinforcement is useless.
It is therefore of utmost importance that the correct shear value of welds be obtained from samples tested. The best known method for obtaining these shear values is by use of the Carlton-Kilpatrick Weld Tester. Hence, the research which the author proposes to perform to determine whether or not the tester is being used improperly, is needed.
Due to the extensive use of Welded Wire Fabric in all phases of construction by the Corps of Engineers, the subject material is of much interest to the author. It was for this reason that the research project on Welded Wire Fabric was selected for thesis work by the author"--Introduction, pages 1-5.
Heagler, John B., 1924-1999
Civil, Architectural and Environmental Engineering
M.S. in Civil Engineering
Missouri School of Mines and Metallurgy
v, 123 pages
© 1957 Ernest Charles Kobs, All rights reserved.
Thesis - Open Access
Library of Congress Subject Headings
Wire products -- Testing
Wire products -- Specifications
Steel, High strength -- Welding
Steel -- Cold working
Strains and stresses
Print OCLC #
Electronic OCLC #
Link to Catalog Recordhttp://laurel.lso.missouri.edu/record=b2614154~S5
Kobs, Ernest Charles, "A comparative determination of weld shearing values in welded wire reinforcement fabric" (1957). Masters Theses. 4161.