Nordtest Method Mechanics 006

							        STEELS FOR CONCRETE REINFORCEMENT:
        SHEAR TESTING OF JOINTS IN
        WELDED FABRICS



1.      SCOPE


         This NORDTEST method describes a procedure to determine the shear
         strength of a cross-joint in welded steel fabrics for concrete
         reinforcement.


2.       FIELD     OF     APPLICATION


         This method applies to all kinds of tack welded or automatic
         resistance           welded   fabrics.


3.      REFERENCE


         NORDTEST NT MECH 001 - Testing machines: Calibration


4.       SYMBOLS        AND     DEFINITIONS


         None.




 published by                           key   words         classification

 NORDTEST                               reinforcing steel   UDC 620.176:691.713
 Tekniikantie 12                        welded fabrics
 FIN-02150 Espoo                        testing             ISSN   0283-7196
 Finland                                shear testing
 www.nordtest.org
                                                - 2 -



5.    METHOD    OF    TESTING


      All parts of the test procedure shall be performed at ambient tem-
      perature of 23 ± 5 °C.


      The testing shall be carried out by qualified persons. If compute-
      rized testing is used, the procedure shall be well documented.


5.1   Apparatus


      Tensile testing machine which allows a uniform increase of force or
      travel. The determination of force shall have an inaccuracy less
      than ±1% (NT MECH 001).


      Fixture        *) according to Fig. 1. The width of the slot shall be 1 mm
                       larger than the diameter of the pulling bar of the test
                      piece.


      NOTE *)         Fixture which allows the supporting bar to rotate may be
                      used. In such case the test will-give a slightly lower
                      value     for   shear   strength.




                                                           1.   Pulling bar
                                                           2.   Supporting bar
                                                           3.   Clamping part
                                                           4.   Locking device
                                                           5.   Support of
                                                                pulling bar
                                                           6 Support against
                                                             bending
                                                           7 Sliding bearing




       Fig. 1. Fixture for shear testing of welds.
                                         -3-



5.2   Test    piece


      A test piece of sufficient length is cut or sawn from the welded
      fabric. Each test piece must contain at least one cross-joint (see
      Fig. 1). When testing welded fabrics with small mesh sizes, the
      length of the pulling bar may include several joints depending on
      the gripping device of the testing machine.


5.3   Procedure


      The test piece must be placed and centered so that the pulling bar
      can move frictionless as shown in Fig. 1. The free end of the
      pulling bar shall be supported in such a way that it will not bend
      during the test. The     force   shall   increase   continuously   until   frac-
      ture occurs. The rate of stress increase shall not exceed 30 N/mm2
      s-1.


6.    TEST     RESULT


      The maximum force in newton (N) as well as the location of the
      fracture shall be recorded.


7.    TEST     REPORT


      The test report shall include the following information if relevant:

             a) Name and address of the testing laboratory
             b) Identification number of the test report
             c) Name and address of the organization or the person who ordered
                the test
             d) Purpose of the test
             e) Method of sampling and other circumstances (date and person
                responsible for the sampling)
             f) Name and address of manufacturer or supplier of the tested object
             g) Name or other identification marks of the tested object
             h) Type, grade and dimensions of tested object
             i) Date of sypply of the tested object
             j) Date of the test
             k) Test method
                                 -4-




1) Conditioning of the test specimens, environmental data during
    the test (temperature, pressure, RH, etc)
m) Identification of the test equipment and instruments used
n) Any deviations from the test method
o) Test results (use SI units)
p) Inaccuracy or uncertainty of the test result
q) Conclusion
r) Data and signature