Section 7.3 is part of the requirements for flatjack calibration. The calibration process includes applying pressure to a flatjack with a compression testing machine. Spacers are used to limit the movement of the bearing plates, so that the flatjack is not over-compressed, which could cause damage to the welds. The thickness of these spacers is specified in Section 7.3, but the existing language recommends spacers that are too thin to prevent damage to the flatjack: The thickness of the spacers shall be equal to approximately 1 times the combined thickness of the two sheets used in fabrication. As stated in Section 5.1.3, the thickness of the sheets used in fabrication typically ranges between 0.024 in. (0.6 mm) and 0.048 in. (1.2 mm). This would result in shim thicknesses between 0.064 in. (1.6 mm) and 0.128 in. (3.3 mm). However, the outside diameter of the inlet/outlet ports is typically 0.125 in. (3.2 mm). With the additional thickness of the two sheets at the connection of the inlet/outlet ports, the uninflated thickness of the flatjack typically ranges from 0.173 in. (4.4 mm) to 0.221 in. (5.6 mm). Some compression and flattening of the inlet/outlet port is acceptable, but the use of shims approximately half of the uninflated thickness of the flatjack is clearly unacceptable and could lead to damage of the flatjack. This ballot proposes to replace the shim thickness language with a thicker, more reasonable requirement. A similar ballot item is proposed for the corresponding language in ASTM C1196, In Situ Compressive Stress Within Solid Unit Masonry Estimated Using Flatjack Measurements.
Keywordsflatjack; in situ; masonry; nondestructive evaluation; Compression testing--masonry/mortar; Nondestructive evaluation (NDE)--concrete/masonry; Compressive modulus; Deformability; Flatjack method; In-situ inspection/analysis; Masonry units;
Ballot Item Approved as C1197-2014 and Pending Publication