There are many empirical methods of fixing the value of the "yield point" used by the 

 various commercial laboratories throughout the country. It is, however, beyond the scope of 

 this pamphlet to go into an analytical discussion of this phase of the subject. 



In order to study the characteristics of the stress-strain diagram indicating the behavior 

 of "Steelcrete" mesh under tensile stress and to determine the values of the significant points of 

 deformation, the hereinafter described tests were conducted under the supervision of Prof. James 

 S. Macgregor of the Columbia University Laboratories, New York City. The results of these 

 tests will be found in the succeeding pages. The behavior of the specimens during test will be 

 noted at a glance from the curve sheet (pages 168 and 169). The approximately straight por- 

 tions of the curves in every case, exceed the unit value of 60,000 pounds per square inch, indi- 

 cating that the "yield point" or "commercial elastic limit" exceeds this value. It will be recalled 

 that the claims for this material, as indicated in the "Steelcrete" handbook are for a value of the 

 "yield point" of not less than 55,000 pounds per square inch, which is greatly exceeded by the 

 results of these tests. 



In order to remove all possible adverse criticism, strict instructions were given Mr. Mac- 

 gregor to select the specimens from the center of a sheet of "Steelcrete" mesh and include at the 

 central portion of the test specimens a bridge (or center connection between two diamonds). The 

 manner in which the test specimens were prepared is described in his letter of transmittal on 

 page 162. See also the photographs on page 163, which illustrate the successive steps re- 

 quired. No more exacting tests could be demanded of any steel reinforcing material than are 

 here given. Not only with the motive of satisfying the most difficult specifications are the results 

 of these tests submitted, but also with the end in view of meeting the increasingly critical de- 

 mands of engineers and designers for detailed information of this character. 



166 



