Masonry Magazine October 1975 Page. 9
BIA Technical Notes
on Brick Construction
Brick Institute of America 1750 Old Meadow Road, McLean, Virginia 22101
TESTING FOR ENGINEERED BRICK MASONRY
DETERMINATION OF ALLOWABLE DESIGN STRESSES
INTRODUCTION
Prior to the development of a rational design procedure for brick masonry, it was sufficient to know that brick masonry units and mortar used were in compliance with the standards outlined in Technical Notes 39, "Testing for Engineered Brick Masonry-Brick and Mortar." These quality control tests provided assurance that the same quality of materials were being used throughout the building project. This did not give any assurance or knowledge as to the actual performance of the masonry in the wall.
With the development of a rational design method, it became important that the architect and/or engineer have knowledge of the expected performance of the brick and mortar, not as individual parts of the wall, but as the total wall system. With this need in mind, this Technical Notes outlines several ASTM Standard Methods of Tests for Masonry Assemblages which will give the architect and/or engineer the ability to predict in-the-wall performance of masonry and determine allowable design stresses.
It is essential in all of the tests described in this Technical Notes that the units, mortar and construction of the assemblage be nearly identical with the materials and methods to be used in the actual construction process. Only in this way can the actual performance of the masonry be accurately predicted.
This Technical Notes will cover ASTM standards for the determination of all necessary design stresses for brick masonry as specified in the design standard, Building Code Requirements for Engineered Brick Masonry, BIA, August 1969, and the model building codes in present-day usage. It will also stipulate the revisions necessary to determine the same properties for hollow brick units. Subsequent issues of Technical Notes will discuss miscellaneous tests for masonry not to be used for design stress determinations. These tests will be used primarily for quality control, material compatability and in-the-wall performance predictions for properties other than strength.
STANDARD METHODS OF TESTS
The ASTM test standards with which this Technical Notes is concerned are contained in Part 18 of the 1974 Annual Book of ASTM Standards. The methods of tests described in Part 18 and listed below should be strictly adhered to; otherwise, the test performed is no longer a standard test and erroneous or misleading results may be obtained. The applicable ASTM standards for masonry are as follows:
Compressive Strength and Modulus of Elasticity: Standard Methods of Test for Compressive Strength of Masonry Prisms, ASTM Designation E 447.
Diagonal Tension (Shear) and Modulus of Rigidity: Standard Method of Test for Diagonal Tension (Shear) in Masonry Assemblages, ASTM Designation E 519.
Standard Methods of Conducting Strength Tests of Panels for Building Construction, ASTM Designation E 72.
Flexural Tensile Strength: Standard Methods of Conducting Strength Tests of Panels for Building Construction, ASTM Designation E 72.
In addition to the above listed standards, the brick and mortar used should conform to the standards listed in Technical Notes 39.
PURPOSE AND APPLICATION OF TESTS
General. If a rational design approach for masonry is employed, it is essential to establish allowable design stresses early in the design process. Present design standard requirements provide two methods to establish these values. Under these requirements, the ultimate compressive strength (f'm) may be determined by (a) prism test, or (b) an approximation based upon brick strength and mortar properties. The prism test method is the preferred method as it provides the designer with more exact information; whereas the approximation method, of necessity, provides more conservative values.
Allowable design stresses may be determined under the design standard, once an ultimate compressive strength of masonry has been determined. However, in some cases, it may be desirable, or necessary, to establish tensile or shear strength to closer tolerances than is obtained by design standard values usually given as a function of ultimate compressive strength or of brick strengths and mortar types. Such conditions may occur when masonry is to be used in prefabricated panels, is to be subjected to unusual loading conditions or when high, early strengths are desirable.
All masonry specimens for establishing design stresses should be built using "inspected workmanship;" that is to say, all head, bed and collar joints should be completely filled (see Technical Notes 7B