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CE479: DESIGN OF BUILDING
COMPONENTS & SYSTEMS
FALL 2012 – J. LIU
MASONRY: Introduction
Topics
History of Masonry Materials
Building Elements / History of Masonry (Some photos courtesy
of Prof. Richard Klingner)
Load-Bearing Buildings
Masonry Units CE479
Photos 747 North LaSalle
Some properties (for design)
Skip to here, Fall
2012, since we
had Ed Gern’s
guest lecture
last Friday.
History of Masonry Materials
Stone
Clay Units
Concrete Masonry Units
Mortars
Stone
First masonry – crude stack of selected natural
stones with earth (soil) packed in between
Later, stone masonry units shaped into polygonal or
squared units with close-fitting joints
Sedimentary rocks (mainly sandstones and
limestones)
Now, most stonework is a thin non-structural veneer
Sawn Units
Stone
Stone Wall,
New Zealand
Dry Stone Wall,
Great Britain
Clay Units / Brick
In use for at least 10,000 years
Sun-dried bricks (adobe) used in Babylon, Egypt, Spain, South America, Indian reserves of U.S., etc.
By 3000 BC, discovered that baking or firing brick greatly increased strength and durability
1858 – introduction of Hoffman kiln, allowed for firing of bricks in continuous process
Concrete Masonry Units
1866 – techniques for making hollow blocks in
wooden molds
Fairly dry mixture of sand, cement, and water was
placed in mold and tamped by hand
Modern concrete blocks manufactured by vibrating
mixture of portland cement, sand, aggregate in a
mold under pressure
Mortars
Early mortars used to fill cracks
May have been clay or clay-straw mixtures
18th century – John Smeaton in England mixed
pozzolana with limestone (with high proportion of
clayey matter) to produce a durable mortar
19th century –portland cement mixed with sand,
lime and water to produce a much stronger mortar
Building Elements
Pyramids
Walls
Columns and Towers
Beams or Lintels
Arches
Vaults and Domes
Pyramids
Simplest way of building is to stack masonry units on
top of one another
Walls
Less material than pyramid construction
Used for retaining earth, fortification of
communities, enclosing buildings
History of Masonry
Columns and Towers
Trajan‟s Column
Rome, 113 AD
Tower of Pisa, 1174
Beams or Lintels
Post-and-lintel construction
Arches
Greater spans are possible with two inclined stone
slabs resting against each other to form a primitive
arch
Corbelled arches
Arches
First true arches about 1400 BC
Wedge-shaped stones (voussoirs) arranged to form
a semicircle
Arches
Shapes
Parabolic
Semi-Circular
Gothic (Pointed, concentrated load at top)
Cable-Arch Analogy
History of Masonry
Vaults and Domes
Vaults – extension of arch construction
Earliest domes formed by corbelling
History of Masonry
Load-Bearing Buildings
Earliest (Rome) were masonry walls with timber
roof with clay tiles
First multi-story examples also by Romans
“cellular” floor layout to provide stability and lateral
resistance
Later multi-story commercial buildings used timber
columns in interior
Thicker exterior walls used at base to provide
resistance to lateral loads
History of Masonry
Masonry Units CE479
Clay Brick
Concrete Block
Clay Bricks
Three grades: SW, MW, NW (ASTM C62)
SW and MW (two grades for hollow brick)
SW – high degree of resistance to frost action even if
permeated with water
MW – moderate degree of weathering resistance
NW – restricted to interior applications; exposure
to weather not an issue
Grade SW required
Also required
whenever brick
in other than
vertical surfaces
(i.e. walls) are in
contact with soil
Clay Bricks
Available in many sizes based generally on a 4x4
inch module (for an overall 24 x 24 inch planning
grid)
Nominal dimensions differ from specified dimensions
by 3/8” mortar joint
Clay Bricks - Hollow
Net cross sectional area between 40 – 75% of
gross cross-sectional area
Effect of reduction in area significant enough that
net cross-section is used in calculations
Larger units
Fewer units for a given wall area
Not heavier (voids)
Concrete Masonry Units
Grades N and S
Grade N – higher strength and resistance to
moisture penetration and severe frost action
Grade S – moderate strength and resistance to
frost action and moisture penetration
For both grades, two types
Type I – moisture controlled unit; meant to limit
shrinkage and cracking
Type II – not moisture controlled
Grade classifications removed
in 1990 ASTM C90
Mortar and Grout
Mortar - used to bond masonry products together. Composed of portland cement, sand, lime and water. Conforms to ASTM C270. Types M and S are used for exterior use, Types S or N used for interior load-bearing walls. Type O used for non-load-bearing interior walls.
Grout - similar to mortar, except used as a filler, especially for vertically-reinforced walls. Specified as either fine-grained or coarse-grained. Conforms to ASTM C476.
Concrete Masonry Units
Solid or hollow
Hollow – less than 75% of solid horizontal cross-
sectional area
In practice, hollow blocks used most frequently
because of reduced weight, ease of handling, ease
of reinforcing, overall economy
Percent solid is usually 50 – 60%
Concrete Masonry Units
Sizes fit into same modular planning grid (as for
clay brick)
Typical nominal size of 8x8x16 inch – “Standard
Block”
Minimum face shell and web thicknesses for load-
bearing units
For example, 1-1/4 in. minimum face thickness and 1
in. minimum for webs for nominal 8 in. unit
Concrete Masonry Units
Concrete Masonry Units
Masonry Elements
Single-Wythe Walls
Solid and Composite Walls
Cavity Walls
Veneer Walls
Columns and Pilasters
Beams and Lintels
Single-Wythe Walls
Used in load-bearing and non-load-bearing
applications
Solid and Composite Walls
Two or more closely spaced wythes joined by
header units or metal ties (cavity filled with mortar
or grout)
Can be reinforced
Course of
headers
Metal Ties
h
t l
Orientation (and names) of
masonry elements in walls
Joint
Reinforcement
Cavity Walls
Typically 2 in. apart and connected with metal ties
Moisture collected in cavity and diverted by
flashing and weep holes to exterior of building
Usually inner wythe load-bearing, outer wythe non-
load-bearing
Lateral loads resisted by bending of both wythes
Joint
Reinforcement
Metal Ties
Veneer Walls
Nonstructural cladding anchored to a structural
backup wall
Metal
wire tie
Expansion Joints
Columns and Pilasters
Columns – isolated vertical members
Pilaster – thickened wall section built integral with
the wall, sometimes described as an „engaged
column‟
Both can be reinforced
Beams and Lintels
Roof beams, floor beams, bond beams, grade
beams
Bond beams – typically located at roof and floor
levels and tie the building around perimeter, act as
chord members
Lintel – horizontal beam spanning over a door or
window opening
All must be reinforced
Stirrups for shear may be required
From Masonry Designer’s Guide, Sixth Edition, The Masonry Society, Boulder, CO, 2010
Example of use of modern Masonry (TGRW Structural
Engineers, Chicago ILL
747 North LaSalle
Chicago, Illinois
Primary Structural System
Exterior Wall System
• Load Bearing CMU
• Composite Metal Deck / Framing
• CMU Shear Walls
• Architectural Split Face CMU and
Glass Curtain Walls
f‟m for clay masonry units
f‟m for concrete masonry units
Masonry Assemblages (Prisms)
Compressive Strength of Concrete
Masonry Prisms Made with Mortar Type S
and Variable Grout Mixes
Juan Manuel Salguero Mendizábal, MS
Thesis, Brigham Young University
Compression Tests
Strength of prisms higher than that of mortar
cubes and lower than masonry units (alone)
Weaker mortar expands laterally faster than
the masonry unit
Masonry confines mortar
Vertical tension cracks develop in masonry
Note: in grouted concrete masonry, compressive
strength of grout shall be equal to or greater than
the compressive strength of the concrete masonry
units
Flexure (Tension) tests
Numerical analysis of concrete block masonry beams under three point bending
Vladimir G. Haach, Graça Vasconcelos , Paulo B. Lourenço
Tension normal
to head joints
Tension parallel
to bed joints
Wall tests
http://www.thenbs.com/topics/Environment/articles/earthBricks.asp
http://www.structuremag.org/article.aspx?articleid=382
For design
Treat units as isotropic
Compressive behavior
Governed by crushing
Tensile behavior
Bond strength between units and mortar
typically controls capacity
