Masonry Magazine October 1975 Page. 13
FIG. 7
Racking Test Frame and Specimen After Testing
FIG. 6
Racking Test Frame and Specimen
Shear or diagonal tensile strength is of considerable concern to structural designers, especially in geographical areas where seismic design is required. Until recently, ASTM standards provided only one method of test for determining shear strength. The method of test is described in ASTM E 72, Standard Methods of Conducting Strength Tests of Panels for Building Construction. This method of test, referred to as the racking load test in the standard, has been supplemented for masonry by ASTM E 519, Standard Method of Test for Diagonal Tension (Shear) in Masonry Assemblages. The E 72 racking load test provides for testing materials and constructions of all types, while E 519 applies only to masonry.
It has long been recognized that the method of test provided for in E 72 introduces compressive stresses into the test specimen at the tie down which cannot be measured. See Figs. 6 and 7 for the testing apparatus used for this test and method of failure. The tie down is required to prevent rotation of the specimen when load is applied. In addition to the uncertainty of the tie-down stresses, this method of test requires a specimen 8 ft by 8 ft (2.438 mx 2.438 m) in size. This method of test generally is available only in large laboratories active in masonry research. On the other hand, E 519 provides a method of test which is easier to perform and provides very reliable data. The smaller specimens, 4 ft by 4 ft (1.219 mx 1.219 m), plus more simplified equipment place this method of test within the capabilities of many private testing facilities. See Figs. 8 and 9 for test setup and loading shoes required for this test.
FIG. 8
Diagonal Tension Test Instrumentation for Modulus of Rigidity
The specimens for both E 72 and E 519 should be constructed using the brick, mortar, bonding pattern and wall thickness that will be utilized in the construc-
FIG. 9
Diagonal Tension Loading Shoe