Page 32 - Design of Reinforced Masonry Structures

CHAPTER 1
INTRODUCTION

1.1 WHAT IS MASONRY?

Masonry is one of the oldest forms of construction known to humans. The term masonry
refers generally to brick, tile, stone, concrete-block etc., or combination there of, bonded
with mortar. However, many different definitions of masonry are in vogue. The International
Building Code (IBC 2009) [1.1] defines masonry as “a built-up construction or combina-
tion of building units or materials of clay, shale, concrete, glass, gypsum, stone or other
approved units bonded together with or without mortar or grout or other accepted methods
of joining.” ASTM E631 defines masonry as “construction usually in mortar, of natural
building stone or manufactured units such as brick, concrete block, adobe, glass, block
tile, manufacture stone, or gypsum block.” The McGraw-Hill Dictionary of Scientific and
Technical Terms defines masonry as “construction of stone or similar materials such as con-
crete or brick.” A commonality in these various definitions is that masonry essentially is an
assemblage of individual units which may be of the same or different kind, and which have
been bonded together in some way to perform intended function. An interesting discussion
on the various definitions can be found in Ref. [1.2].

1.2 PLAIN AND REINFORCED MASONRY

From a structural engineering perspective, masonry is classified as plain or unreinforced
masonry and reinforced masonry. Plain masonry refers to construction from natural or
manufactured building units of burned clay, concrete, stone, glass, gypsum, or other simi-
lar building units or combination thereof, made to be bonded together by a cementitious
agent. The strength of plain masonry depends primarily on the high compressive strength
of masonry units. Plain masonry, like plain concrete, possesses little tensile strength.

Therefore, it cannot be used as an efficient building material for structures or structural
elements that must resist tensile forces. The poor tensile strength of plain masonry makes it
unsuitable for horizontal spanning structural elements such as beams and slabs, which resist
loads in flexure and, thereby, are subjected to tensile stresses. Similarly, plain masonry also
cannot be used for columns subjected to eccentric loads that will produce tensile stresses in
them. To overcome this drawback, plain masonry is strengthened with reinforcing materials
such as steel bars, which greatly enhance both its tensile as well as compressive strength.
This later form of masonry construction is referred to as reinforced masonry. Stated simply,
reinforced masonry construction is “masonry construction in which reinforcement acting in
conjunction with the masonry is used to resist forces” [1.1]. Reinforced grouted masonry
and reinforced hollow unit masonry are subheads that are used in the building codes to
characterize different forms of reinforced masonry construction.

1.1