Page 100 - Design of Reinforced Masonry Structures

2.52 CHAPTER TWO

approach” to construction. The impetus for the systems was provided by federal agencies
and others in an attempt to lower on-site construction costs [2.55, 2.56].
Prefabricated masonry panels are produced in many different ways. There are practi-
cally as many fabrication methods as there are firms producing these panels. Typically,
these methods have been classified into five general categories: hand-laying, casting, spe-
cial equipment, special units, and special mortars [2.55, 2.56]. A comprehensive discussion
on various aspects of prefabricated masonry can be found in Ref. [2.55].
Panels have been prefabricated from both brick and concrete masonry units. They are
designed in the same manner as hollow clay masonry walls. Each panel is self-contained
structural system capable of handling the loads that are encountered during lifting, trans-
portation, and installation. During lifting, the entire panel is hanging from the connectors at
or near its top, which subjects the lower portion of the panel to tension. As a result, the panel
behaves as a beam to support its own load. To preclude the possibility of masonry cracking
in the tension zone, designers use standard mortar and special bricks for designing panels.
Prefabricated masonry panels offer great design flexibility since each one is custom
made. However, on a project, there could be hundreds of panels, each one with a different
configuration. Panels are produced to accommodate precast pieces (such as for window
sills), and steel embedments for mounting windows. Also, complex shapes, such as sloping
sills, arches, corbelled soffits, or articulated parapets that would be nearly impossible to
build on the jobsite can be easily made in a factory [2.57]. Figure 2.50 shows prefabricated
exterior load-bearing panels installed in building in Denver. The panels are 8-in. thick split-
face concrete masonry laid up with a thin bed adhesive material. The bearing surfaces of
the block units are ground to give better height control. The panels were preassembled at
a factory site by Masonry Systems, Inc., Denver and hauled 25 mi to the jobsite for instal-
lation. Figure 2.51 shows a prefabricated curved brick panel being cured in a plant prior
to shipping.

FIGURE 2.50 Preassembled exterior load-bearing panels. (Courtesy: NCMA.)