Masonry Design | 69
code is that designers need to provide the movement
joint locations.
Further support for this interpretation is based
upon how the locations of movement joints affect
various performance aspects of the walls that
only the designer can address. These include:
a. The spacing and location of CMU joints
affect the size of the joints and the type
of the horizontal reinforcement. While TMS
402 does not say how to design the joints,
TEK Notes from the National Concrete
Masonry Institute (NCMA) provide guid-
ance for CMU walls and Technical Notes
from the Brick Industry Association (BIA)
provide guidance for clay masonry.
Specifically, the NCMA TEK notes have
empirical and engineered methods for
sizing and spacing joints and selecting
horizontal reinforcement for CMU to
accommodate shrinkage only.
b. The spacing of movement joints
determines the length of, and the design
of, the shear walls.
c. The placement of movement joints can
affect the design of masonry beams and
lintels since the position of movement
joints relative to an opening determines
whether arching action can be used in the
design.
d. The locations of the movement joints can
affect the axial design of the wall at
concentrated loads. If a movement joint is
placed near a concentrated load, the wall
may not be able to distribute the concen-
trated load such that the wall can ade
quately provide sufficient support. If addi-
tional support is needed, a pilaster may be
required near the movement joint.
e. A movement joint placed close to an open-
ing can result in an undersized jamb pier.
f. Movement joints can assist in accommo-
dating differential movement.
Hopefully, it is clear that locating movement joints
is not just about accommodating shrinkage and
contraction of the material. Joint placement can
affect so much of the design that is not within the
expertise of the contractor. Thus, the task of designing
and locating movement joints is a design
responsibility from the code and, in my opinion,
should not be assigned to the mason contractor.
Q: In our office, a common question is whether
to design reinforced masonry walls with horizontal
bond beams or horizontal joint reinforcement.
Can you provide any suggestions?
A: Many design firms work in various states
and the answer can vary by region. While bond
beams and masonry are generally part of many
designs for the tops of walls and for openings,
practice varies for how to reinforce the field of the
walls. So, the short answer is that the choice can
be determined by one or more of the following:
1. regional practice,
2. desired structural performance,
3. controlling thermal movement.
Let’s consider each separately:
1. Regional Practice:
In some western state, engineers design their
walls fully grouted for seismic performance.
In addition, they prefer bond beams for hori-
zontal reinforcement. In the mid-west and
eastern states, partial grouting is more com-
mon. In these areas, engineers often choose
horizontal joint reinforcement unless there is a
design condition that requires bond beams.
2. Desired Structural Performance:
a. The purpose of the horizontal reinforce-
ment must first be established. If the sole
purpose is for crack control, either bond
beams or horizontal joint reinforcement
may be used. If the horizontal reinforce