(1)Associate Professor, Department of Construction Science, Texas A&M University, College Station,Texas – 77840, USA. jm-nichols@tamu.edu

(2)Associate Professor, Department of Architecture, Texas A&M University, College Station,Texas – 77840, USA. kglowacki@tamu.edu

(3)Assistant Dean, College of Architecture, Texas A&M University, College Station,Texas – 77840, USA. leslief@tamu.edu

ABSTRACT Masonry veneer provides the outer surface of many different buildings in the world. Traditional veneer masonry is fastened to a frame using masonry ties of different forms. The earliest and simplest assumption was that masonry or stone elements would not support tension stresses or forces. Development of cement products and the improvements in the manufacture of clay bricks lead to observation that masonry could sustain a small tensile force or stress, particularly for transient loads, such as wind or earthquake loads. In 1980, two Australian researchers developed a test that was a variation on the standard beam test to determine flexural strength of masonry units. The test, now termed the Bond Wrench Test, allowed for the testing of all joints in a masonry prism, not just the one tested in a beam test. The bond wrench provides a different sample population of results when compared to the beam test for a single prism. Two popular versions of the bond wrench were developed before 2000 CE, the American ASTM bond wrench and the Australian Standard (AS) bond wrench. The two wrenches are distinctly different. In the last few years, two additional wrenches were designed and manufactured at our university. These wrenches are termed the TAMU unbalanced bond wrench and the TAMU balanced bond wrench. A set of comparison results were established using the ASTM E-518 prism beam test to provide a secondary measure of the estimated bond strength. The purpose of this paper is to compare experimental results for the different wrenches to determine the precision of the four bond wrenches and the standard beam test. The secondary purpose is to determine the biases, and establish the likely reasons for the biases between the different wrenches. The results show that the TAMU bond wrenches provide a smaller co-efficient of variation on the results, provide consistent mean results and are significantly cheaper to construct in any metal-shop.

KEYWORDS: bond strength; flexural stress; masonry; bond wrench; beam test.