There are four ballot items: 1. Remove Section 4.4.1 - Load Frame Stiffness Requirement : The task group would like to remove section 4.4.1 which has a lateral and longitudinal stiffness requirement for load frames. Section 4.4.1 is not used in any calculation of machine bearing capacity or load capacity. Section 4.4.2 is used to calculate the load capacity of machines and an example of the calculation is giving in appendix X1. The origin of the values for lateral and longitudinal stiffness was from a note that once appeared in ACI testing requirements for high strength concrete. This note has subsequently been dropped from the ACI requirements. The requirements of section 4.4.2 yield nearly the same longitudinal stiffness values as 4.4.1. The longitudinal stiffness of a test machine significantly affects the post peak failure mode but the peak load is relatively insensitive to machine flexibility. The task group believes that 4.4.2 adequately covers the stiffness requirements of the load frame and 4.4.1 can be removed. 2. Revise Note 2 - Add Reference to Fig A1.3 Note 2 describes the preferred orientation of test specimens in testing machines with significant differences in lateral stiffness. Figure A1.3 shows and example of the situation discussed in note 2. Adding a reference to the figure will help clarify the note. 3. Revise Section 4.7.8 Hemispherical Head Requirement The task group would like to add an exemption to the 2 inch minimum thickness requirement for the spherical portion of a test head. In a hemispherical head of non-integral construction, a test head where the spherical portion of the head is mechanically fastened to the back of the platen, portions of this spherical bearing piece can, and typically will, be thinner than 2 inches thick. This brings the design and bearing calculations described in section 4.10 and Annex 1; into conflict with section 4.7.8 which states any section less than 2 inches thick should be considered as a spacer for bearing calculations. This conflict was not intended. This spherical section is almost wholly contained and supported by the socket section of the head. 4. Add A1.1.1 and A1.1.2 - Bearing Area Calculation Annex A1 gives geometric solutions to determine the allowable bearing areas for platens. After reviewing these solutions the task group found that in almost all cases these solutions can be expressed more simply as mathematical calculations. This ballot would add two new subsections giving these calculations to make the standard easier to use by the typical testing laboratory.
bearing block; bearing surface; load frame; platen; spacer; testing machine;
Citing ASTM Standards
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