ASTM C1531-22 PDF

SIGNIFICANCE AND USE 5.1 This test method provides a means of evaluating the horizontal in-plane shear behavior of mortar joints in existing unreinforced masonry assemblies (see Note 2). Note 2: The masonry mortar joint shear strength index obtained by this test method can be related to the masonry wall shear strength by relationships contained in referencing Codes and Standards. For example, formulas relating shear index to wall shear strength are found in Chapter A1 of the International Existing Building Code and Chapter 11 of the Seismic Evaluation and Retrofit of Existing Buildings, ASCE Standard ASCE/SEI 41. The user of this standard is cautioned that these shear strength relationships are typically empirical relationships based on tests of early 20th-century unreinforced brick masonry. These relationships typically assume that wall shear strength is limited by shear of the mortar joints rather than shear through the units 5.2 For hollow ungrouted or solid unit masonry construction the shear strength index is measured only for the mortar bed joints vertically adjacent to the unit being tested. When testing hollow ungrouted masonry construction, the shear strength index is based on the horizontal interface between the mortar and the test unit and the masonry above and below the test unit. In the case of multi-wythe construction, the measured mortar joint shear strength index is applicable only to the wythe in which the test unit is located; no headers shall exist immediately above or below the test unit. The contribution of any existing collar joint mortar to the measured shear strength index is neglected, and this may lead to an overestimate of the shear strength index (see Note 3). Note 3: Some documents that reference this test method, including ASCE/SEI 41, include a reduction factor to account for the contribution of a filled collar joint to the measured shear strength index. 5.3 The test procedure listed for Method A may be conducted as an extension of Test Method C1... SCOPE 1.1 These test methods cover procedures for the determination of the average in situ mortar joint shear strength index in existing unreinforced solid-unit and ungrouted hollow-unit masonry built with clay or concrete units. Three methods are provided: 1.1.1 Method A (with Flatjacks Controlling Normal Compressive Stress)—For determining mortar joint shear strength index when the state of normal compressive stress at the test site is controlled during the test using the flatjack method described in Test Method C1197. Horizontal displacement of the test unit is monitored throughout the test. The test setup for Method A is shown in Fig. 1. FIG. 1 Test Setup—Method A Note 1: A paper2 by Francesco Graziotti et. al of Univ. of Pavia included in ASTM STP 1612 discusses alternative methods for interpreting Method A testing results. 1.1.2 Method B (without Flatjacks Controlling Normal Compressive Stress)—For determining mortar joint shear strength index when using an estimate of the normal compressive stress at the location of the test site. Horizontal displacement of the test unit is not monitored during this procedure. The test set up for Method B is shown in Fig. 2. FIG. 2 Test Setup—Method B 1.1.3 Method C (with Flatjack Applying Horizontal Load)—For determining mortar joint shear strength index using an estimate of the normal compressive stress at the location of the test site, as shown in Fig. 3. Horizontal displacement of the test unit is generally not measured during this procedure. FIG. 3 Test Setup—Method C 1.2 The text of this standard refers to notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. 1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for informat...