|
Items in cart [0] |
Questions? Call 888-624-8373 |
| ||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 29
P A R T T W O
PRESIDING CHAIRMAN
John Knox Shear
Technology of Building
With Masonry
M R. S H ~ A R: In this second session we turn our attention to the sub-
ject of technology of building with masonry. Having started on an aesthetic
basis, which ~ must say ~ commend, we must nevertheless move quickly
into things equally basic but in another dimension.
29
OCR for page 30
Or:
OCR for page 31
Reinforced Brick Masonry
R . ) O H N K N O ~ S H E A R: The tech~ol-
ogy of buiZ3ing with masonry presents us with
two men, an engineer and an architect, both
coming out of backgrounds of broad experi-
ence. Our first speaker, Mr. Walter L. Dickey,
has had a broad background, which has pre-
pared him for his discussion today. Mr. Dickey
has worked at it actively and practicalZy, and
has for many years rzow worked at it in the
theoretical realm as an engineer. He is the
chief structural engineer for the Bechtel Cor
THIS is a description and discussion of the
combining of modern reinforcing techniques
with ancient and venerable brickwork, to solve
problems of modern architectural expression
and construction.
The subject of Reinforcect Grouted Brick
Masonry is one that is noted to tie into almost
Walter L. Dickey
Bechtel Corporation,
San Francisco, Calif.
poration. He is a civil engineering graduate of
the GaZifornia :Institute of Technology and
worked as a bricklayer whiZe doing graduate
work on masonry structures.
Mr. Dickey is a member of the American
Society of Civil Engineers, the American
Standards Association Masonry Committee
the Structural Engineers Association of CaZi-
fornia' the Pacific Coast BuiZ6ing Officials
Conference and the American Ordinance
Association.
all the other topics of this conference. it
provides flexibility in architectural design
to achieve effectively the `'Aesthetic De-
n~ancls of Contemporary Architecture," in-
cluding n~inimizing the norn~ally great need
for "era cl; filllers." It provides for combinations
of "Colors and Textures" in almost anv type
J ~
31
OCR for page 32
of pattern that might be desired. It provicles
for the achievement of "Modular Design,"
even the mixture of different modular systems
within the same wall. :[t provicles for aIn~ost any
'Veneer" surfacing desired. It has been used
in lieu of "applied veneer" in many instances.
In so using it, the "Veneer ancT Face-bonded
walls' would be homogenized with the struc-
ture.
The "TLern~al Performances is excellent.
"Ceramic Veneer" can be used in this type
construction. Also there have been instances
in which "Natural Stone" was used as one
wythe of the Reinforced Grouted Masonry.
"Marble and Granite" night have been used
although ~ do not know of specific instances.
"Brick anc! Tile Research" has been conductecT
extensively evaluating this type of construc-
tion as well as providing information that can
be used in unreinforced masonry. "In-the-
wall Costs" are relatively goocT, and "Main-
tenance of Industrial and Public Buildings"
is minimized by this type of construction. :Et
has been used in "Residential Design" with
striking results ancT is effective in construction
to provide not only curtains but also structural
shear elements. It has been used on "Hospi-
tals" such as the large Veterans Hospital just
outside of Los Angeles at SepuIveda. :[t has
not only been used in "Schools" but the Cali-
fornia State Division of Architecture, responsi-
ble for the design and construction of safe
school buildings, was one of the leading or-
ganizations in the initial development of the
technique. ~
So it touches the many facets of a Modern
Masonry Conference.
AUTHOR s COMBINATION OF PRACTICE
ran
AND 1 HEORY
The author's early experience was on con
struction jobs as bricklayer laborer, hod carrier,
brick layer, and brick layer foreman, primarily
32
on brick and tile walls, partitions, etc. The-
oretical training was at the California Institute
of Tecl~nology with graduate work, particularly
in masonry structures. Since then experience
was as structural engineer in private practice
ancT structural engineer for the power division
of Bechte] Corporation. It was in the latter
capacity that there was the responsibility for
the design of one of the largest brick builctings
in the western area, a power plant some 800
feet long, 90 feet high and 400 feet wide.
There were of course many other similarly in-
teresting responsibilities, in the tremendous
and widespreacT activities of Bechte! Corpora-
tion.
The above theoretical and engineering train-
ing was valuable, but in design the practical
experience was of even more value and aid in
visualizing the problen~s of combining brick,
mortar, grout and reinforcing into a 1~o~no-
geneous structural element. The problems of
design are no snore complex than design of
reinforced concrete, but details of assembly
sonnetizes tax the experience and practical
ingenuity of the (resigner.
WHAT [S RBM AND RGBM?
The terms RBM~an(1 RGBM are abbrevia-
tions of "Reinforced Brick Masonry" and
"Reinforced Grouted Brick Masonry.', These
should be definecl of course, since they are the
subject of this paper. RGBM for some time
referred to the reinforced grouted world that
was cleveloped as a new method of construc-
tion, and which became most generally popu-
lar and effective. it consists of wythes of ma-
sonry with grout poured between, i.e. a grout
collar joint to provide for reinforcing, to tie
the wythes together, and to form a weather
barrier. There are other founts of reinforced
masonry but this is presently the most effec-
tive.... The rather clumsy term RGBM is
now being dropped for the more euphonious
RBM.
OCR for page 33
RBM is now being usecT as the generic
terns for all reinforced brick masonry, wheth-
er of the more popular grouted type, or the
type with reinforcing in bee] joints, or in filler]
cells or holes in the brick units, as will be dis-
cussec! later.
Frown an architect's standpoint, RBM seems
to offer the designer greater flexibility in treat-
n~ent ancT use of finisher] materials than any
other comparable material or method. There
is little limitation in selection of masonry
materials, of patterns, of types, of sizes, etc.
The choice is greater even than in unreinforced
masonry. In adclition the finish surface or
material is not applied merely as a skin or
covering, it serves as part of the structure as
well. It can be said that the finish becomes an
active loacI-carrying participant rather than
a passive Toacl, or burden. It is a mystery why
so little is known about the use of this n~ethoc!
except in the area in which it was initially cle-
veloped.
HISTORY
RBM was reported to have been user] 140
Years ago in Englanc! ancI later in France and in
TncTia. The author's first personal experience
with reinforced brickwor]; was in 1911 on the
construction of the State Hospital at Agnew.
The reinforcing consisted of flat steed straps
in the bed joints with notches or holes for
vertical bars. The installation was not well re-
garclecT by the masons, their felt tint "they
had built the Pyran~icis without steel and
steed was not necessary." However, while rein-
forcen~ent has been used for a long tinge ancI
sometimes rather haphazarcIly, to strengthen
n~asonr,v, reinforced brick masonry in the
modern sense is a relatively new construction
requiring new design procedures and new con-
struction n~ethocis. In the past 20 years espe-
ciaTly these have been developed from experi-
mental investigations ancT observations of con-
struction of hundreds of buildings uncler
orclinar,v vertical Toacis, anc! uncler the influ-
ence of earthquakes. The trained and practical
observation as well as the Iaborator,v work
has confirn~ec! the soundness of tile scheme.
LONG BEACH EARTHQUAKE
RBM was developed ant! has experienced
its greatest use and improvement in the
Southern California area. It was there that
the Long Beach quake of 1933 shook clown
the cheaply built, poorly designecl, loosely
tied, boom built, brick structures. Brick were
salvagecT and cleaned front the debris be; the
simple expedient of sweeping off tile loose,
powdery mortar crust. It was said at the
tinge tint the purpose of the mortar nest
have been to "keep the brick apart" rather
than to bond then together. There was an
example of a stack of brick on a pallet adjacent
to a collapsed brick structure. The pile was
still unclisturbecT anc] standing relatively true,
not having mortar to keep the brick apart,
while the brick building was a pile of debris
sin~ilar to the photo below of the church in
Bakersfield.
~,~ ,,, ~ ~ ~ ~ · ,,, ~ ~ ~ T~ ~ ~ ~ ~ ~ : ~
OLD BRICK CHURCH AFTER BAKERSFIELD
EARTHQUAKE OF 1952
The old church in the fore:,round' built with old
brick masonry desi:,n methods' was completely
destroyed. The new annex in the background'
built of 8" RBM' is unharmed.
33
OCR for page 34
Some of the brick structures that were clef
Polished by the Long Beach quake were iden
tical to many of the brick structures now built
in the East (since the last big earthquake
occurred in the area ~ . The first quake, for
ninny, will probably be the last. We do not
predict a quake soon, but the records, as shown
on the seismic chart, show quakes have oc-
currecT here in the past.
DESTRUCTIVE AND NEAR DESTRUCTIVE EARTHQUAKES
OF THE U. S. THROUGH 1950
While the greatest number of earthquakes has
occurred in the West' particularly California,
some of the largest on record have occurred in
the Eastern area.
Since the builctings referred to had not been
designed to resist any lateral force the factor of
safety against lateral force might be FS ~ O--
O so Lence the collapse.
The buildings that suffered worst as a group
were the school buildings. These hac] certain
unclesirable characteristics in con non. Tilers
was excessive, massive, ornate gingerbread!
"embellishment" arounc! the top. There were
Digit winclow openings, in~posing top-heavy
entrances, a minimum of structural material
to back up the fancy facing, a n~inin~um of
roof structure and detail connection-eEect
of unclue emphasis of a competitive bidcling
system inadequate inspection of the quality
with resultant n~inin~u~n cement content, and
low regard for workmanship.
34
The sight and Sensory of brick buildings
collapsed as piles of debris was a factor that
practically elin~inate(1 the popular pendant
for brick production, especially perhaps since
so much "used" brick was available in such
good condition, unbroken and hardly stained.
It was obvious then that a different type of
construction nest be developecl.
DEVELOPMENT OF RBM
Recognizing the advantages of bricT; con-
struction and the serious need for developing
structures to resist quakes safely, the Southern
California groups initiated active programs of
engineering study. Mr. Harry Bolin was one
of the aggressive and far-seeing engineers who
cIid much to develop the scheme of grouted
reinforced masonry; and to conduct tests which
verified the soundness of the various factors
He established facts where there hack been but
theory before.
One series of tests was especially interesting
and valuable. It establiished that grout could,
and should, be pourer] very wet, even "sloppy, ~
apparently violating the engineering concept
of "water cement ratio.' The grout might be
poured, with a W/C ratio to result in 1600
psi concrete, but due to the absorption of the
brick ant] the subsequent curing effect, the
grout core when actually tested couIcl develop
5000-6000 psi in 78 days. Also, when poured
tllusly, the bond was extremely laigh.
The first noteworthy exan~ple of that pro-
gran~ was the Vermont Avenue School built in
1937.
Many types of masonry were attempted
special shapes were (leveloped The Grout
Lock Brick and the Port Costa Key Brick
shown in the sketches are two. The ~ne-
chanical key to the brick is a desirable feature,
elin~inating one of the hazards of poor world
manship, namely poor bond. However, sinus
OCR for page 35
Scab forcing
Is. 7
Z~Gro~f \ . /
~ . - 7 me, _ A ~ ~ , - _
comer ~
. dS"WALL CORNER CONSTRUCTION
DETAI L ~ 124"s 134~ PI ER
In: ~
if ~e,~forceo' fork
AFROS
L~ Is.
~ IS ~ ~ ~ ~7fl
/f~c CO LU M N ~ BE AM
8 E A M BR [C K C O N STRU CTION
PORT COSTA KEY BRICK GROUTED MASONRY
Sketch at upper ri,,ht shows typical wall sec-
tions constructed with special brick known as
`-Groutlock'' brick. The beveled ed:,es of these
units provide more space for both vertical and
horizontal reinforcing' and give the impression
of mechanical bond. Although such special
shaped brick as shown here' on the Port Costa
Key brick details' and L's and soaps used on
the Vermont School have been developed in
some areas for RBM, it can be designed and
constructed with the conventional brick shapes
and sizes found all over the country.
Slcetcl~ at lower right illustrates various REM
wall sections and thicknesses constructed with
modular brick of conventional size. Variations
are possible as brick sizes vary locally. In most
cases the variation will be largely in the over-all
wall thickness when brick of different widths
are used. Thickness of vertical or horizontal
joints is determined by the size of reinforcing
bars used. A minimum of ]/4 in. clearance
should be maintained between the bars and the
masonry units except that No. 2 (~/4 in.) liars
may lie used in ]/2 in. joints.
1 \
3/~. ~ ~ 2^'0.C. ~OQ':O~TALLY - 19~0.C VLRTICALLY
PLAN OF 7 ~ WALL
BLA M bR,CK
Grabs
~lLrCK
TYPICAL GROUTLOCK BRICK CONSTRUCTION
>40~1~AL SIZE OF bR\C~ ASSU "CD A5 23 ~4 ~ d'
' ~W
In'
four rl`L
PtA CRAV[L \
GQOLUT rail ~
-I ~ ~
1' l
l
>' For arl~roQc` - c'4r
NIL ~ '~'-1
~'CLlAQAbCt ~ Rt~rORCC"C~7
i ~ ALL' -I
~ afar
ALTER,4~` POSITION.
~ or HORIZONTAL b^QS
1 ~F7- (THESC 64~5T BL.. 2
~,r Jolt 15 'I')
~ .
~ .
.,1 1
| ;~' ~. rod Q~l~ro~cc~c~T
I'd- Ail 3A'1.
~\'l~ (LtA4A>`C£ TO 411NtO4Ct - C - T
5' WALL ;
. ~ l .
.
'
. //~/
f ~
~ -~. ~
~ ~r ~
~ ~ . Amp. .
j HA' loll 5''- yell a/
~ , . 1 ,
| 13'6 WALL ;
|- -- - -
~;
~1~1
~11~1~
;~h 1'i 34 anti 3~ I
L 12 /s WALL i
VARIOUS RBM WALL SECTIONS WITH CONVENTIONAL
SIZE BRICK
35
OCR for page 36
taneousT:, research in mortar and grout had
disclosed the fact that bond between brick
and mortar couIc3 be so good as to be better
than tile strength of the material, under prop-
er conditions. Therefore there was no need for
special sllapes, ordinary common brick of any
shape and size would clot The only special con-
sicleration was good workmanship, i.e., clean
moist brick, good plastic cement mortar,
sloppy wet cen~ent grout. Other masonry units
such as tile, stone, concrete block. etc., could
serve.
PRESENT RBM DATA
There is a wealth of material publishec! on
RBM but two publications are especially rec-
on~n~encled as covering flee subject quite thor-
oughly and in considerable detail. One is the
"Technical Notes on Brick and Tile," Struc-
tural Clay Products Institute, Volume I, No.
I, 7, 3' and 4. Another is the very excellent
book, "Reinforced Brick Masonry and Lateral:
Force Design," by Mr. Harr,v C. Plun~mer of
the Structural Clay Products Institute and Mr.
John A. Blume, one of the leading structural
engineers of the west.
A good guide to the design of RBM, in the
western areas especially, is the Uniform
Building Code developer! by the International
Conference of Building Officials. One of our
Conference Con~n~ittees also prepared a book-
let as a practical aid to inspectors of RBM,
"Reinforced Grouted Brick Masonry Field
Inspectors Handbook."
These describe construction procedures and
some effective methods to aid in accon~plish-
ing teens. They emphasize the importance of
good workmanship and continuous inspection
to achieve it.
The importance of the inspection is to be
noted in the different values of design strength
which are permitted in the Design Tables of
the UBC. The clesign strength permitted is
considerably higher for continuously inspected
structures than for those not inspected.
36
TYPES OF RBiM
As mentioned before there are many edec-
tive types of Reinforced Brick Masonry. Some
of these are listed below. The item in common
is the use of masonry elements and reinforcing
boncled together by a cen~entitious material'
generally cement mortar an(1 grout.
Stone Masonry
Stones set in mortar
Cavity NVall lMasonr:
Space provided between wythes
Reinforced Hollow Unit Masonry
The units contain hollow spaces, and
reinforcing may be in joints or in filled
cells.
Reinforce(1 Solid Masonry
Solid Masonry with the bars in the becT
joint or between soaps' for example.
(Includes SCR 8z Brix Blox, etc.:
Reinforced Groutec! Masonry
Wythes bonded together with grout
collar joint between.
Composite Construction
Might be similar to reinforced grouted
masonry, with hollow units in one
wythe and solid in another.
I~nprovec] use of mortar was developed in
the search for adequate reinforcing methods.
The mortar of the new RBM is almost as
unique a feature as is the reinforcing, ant! is
a feature that insures the action of RBM as
a homogeneous element.
Two of the above, Composite, referred to
frequently, and SCR are describe(1 in noose
detail. The Bricl: Block, a form of reinforce
soli(1 masonry, is mentioned briefly.
There have been quite extensive tests on
many of the aspects of the above types, too
numerous to mention in this paper other than
merely in passing, and to emphasize that they
verify the theories.
OCR for page 37
COXIPOS3[TE GROUTED MASONRY 800. /'SC/i?4C~__~
CONSTRUCTION /; ~ --- ~ :~ -
Tllis may be of many types' and one, tile
combination of structural glazed tile ancI co~n-
n~on brick. is described here as an example.
This type was used in a plant in which there
were laboratory, ofI;ce, and storage rooms.
Along one side wall there was an outer finish
face, which was entirely of a Norman unit
stretcher bond. The inner wythe in the storage
area was a bunko brick, economical of n~ate-
rial and labor. The laboratory was formed by
intersecting walIs of reinforced hollow glazed
tile and by having the interior wythes of the
exterior wall co~nposec] of glazer! tile, bondec]
to the grout collar similar to the brick. Then
in tee office space adjacent in this same ex-
terior wall, the interior wythe was a buff face
brick in lieu of the Norman, jumbo or glazer:]
tile. That particular wall was an example, to a
sn~all clegree, of the freedom and functional
expression that might be achieved with REM.
The (resign of such composite shapes re-
quires a thorough visualization of stress paths,
requiring that one cleIve into the higher orders
of witchcraft.
Recognizing the uncertainties, the author
participated in some tests which were neatly on
reinforced beans which verified nanny items
rather satisfactorily. Results of the tests of clay
tile beans with their complex interior shapes
are indicates] on the chart.
The chart (right above) indicates that n~a-
sonry, in stack bond, complies with the design
values permitted. It also emphasizes that ~na-
sonry is a good n~aterial on its own, without
reinforcing. It indicates also the comparative
value of stack vs. running bond. Since the stack
bond performed as well as design values wouIc]
require, we should note that the running bond
is so much better than the stack bond, rather
than stating that the stack bond is so much
worse than the running bond. In other words:
600,
500 .
` 400.
3 Boo .
200,
O O
50
/' ~\ ["'a- ~ ~ ~ ~ ~ ~0~0
SHOOTS'
/
/ -I ~
,. T~
- SICK r~
TESTS OF STRUCTURAL CLAY TILE
The type tested is shown as above. The three
arrows on Design Curve show Calculated values
for ``uninspected'', ``inspected,?, ~`ultimate.~' This
illustrates' not how poor stack Lund is' but how
excellent is masonry.
"The glass is half full!" not "the glass is half
empty!"
The sections of composite brick and tile con-
struction iTIustratecT on next page are for fur-
ther clarification of the type.
The test ~netho(1 which was used to check
the increase of strength achieved by the grout
as poured between the brick is shown in the
sketch below.
Grout should be poured into place very wet
to make thorough intimate bond with tile
TYPICAL MASONRY TEST PRISM
Well oiled, non- absorbent
/: end p I ates.
,: Typicai for job.
it/
/ ~
Swell oiled, non-absorbent base plate.
tA OQTAQ
~^,`~:~ | GROUT
37
OCR for page 38
OCR for page 40
OCR for page 41
OCR for page 42
OCR for page 43
OCR for page 44
OCR for page 45
OCR for page 46
OCR for page 47
OCR for page 48
OCR for page 50
Representative terms from entire chapter:
reinforced concrete
masonry and reinforcing. Tile porous volume
of masonry then sucks the water from the
grout core leaving it with an excellent. edective
water cement ratio. The tests showed that the
grout samples developed 1600 psi in 78
REM AD\TANTAGES Savings In Structural Steel Support
Savings In Steel Reinforcing
It is recognized that masonry shows less
shrinkage cracking than concrete ant] therefore
customarily less temperature reinforcing is re-
quired for masonry walls than for concrete
walls. In addition unreinforced rnasonr,v panels
can be included between reinforced portions
for even greater savings. These savings in rein-
forcing steel night be very important, espe-
cially (luring tinges of acute steel shortages. In
some instances the supporting structure can
be incorporated in flee masonry with no acldi-
tional reinforcing.
The table below shows tile comparison of
temperature steel required in masonry walls of
various thicknesses as contoured to that re-
quirecT for reinforced concrete walls. Concrete
requires .0025 x area each way, but masonry
.007 i; area, or .001 ~ area if divicled equally
vertically anc! horizontally, i.e. concrete re-
quires 7~/' tinges as much as n~asonr~
NIININIUM NVALL REINFORCING ( UBC )
REINFORCED BRICK
Wall As/ft. ~bars & Weight Weight
(to) I ea. way spcg psf i psf
6"
8'
1
10" 1 .120
.072 ~ ~9
~18 1
REV 1
.096 ~6
~@,13
~11
~lv
.144 ~ W;~VR~)
34~?,16
Advantage can be taken of tile bigly com-
pressive strength of masonry to carry vertical
Toads eRectively within the wall. Then, if there
is other consideration, SUCH as lateral force or
moment in~pose(l, special reinforcing can be
added. In this way many building types can be
constructed without requirement for support-
ing structural steel.
E CONOMY OF REINFORCING AND LAYING
Economy of placemerzt is effected since tile
reinforcing can be placed easily and econo~ni-
cally by tile masons as desired.
Workmanship is important in all masonry
work, but some of tile uncertainty is removed
by tile pouring of the grout. It provides a
weather barrier. It bonds tile wytiles securely
together, it fills the portions of bed joint that
may not Lave been filled full, it fills the back
REINFORCED CONCRETE
l l
bars & ~As/ft. ~Wall
spcg ea. way (~)
1 ~.18 6"
1.22 ~ ~@,8
~(~13
.65
. ~-
1.62 ~@J5~' .24
~ 34@,10
I . _
8"
.81 ~2.04 ~8 .30 10"
~12 1
_ ~_ ~I
.98 1 2.431 ~6~'
~(7,10
.36 1 12"
39
of the head joints providing good bond in tee
event the mason Pact not used full shoved
joints. In fact some careful workmen leave the
inside edges of the joint open so the grout will
flow in and develop good mechanical bond in
addition to adhesion. When RGBM was ini-
tiated into the Utah area in a power plant
program, it was necessary for the author to
spend a few days indoctrinating the masons.
T ~ ~ r ~
mere are some exan~ples ot what tl~e masons
were told:
"Don't spread such a full bed- it squeezes out
into the grout space.
"Put more water in the grout so it is sloppy
and pours easier.
"Don't put so much mortar on the heac! joints,
it's better if the back edge is not full than for
mortar to extrucle or drop into grout space.
`'Don't furrow the bed-merely swipe it.
"Don't wet the brick too notch, they won't
dry up the grout core.
"Don't put those headers across do it as
shown in the drawings.
'Don't put that angle over the opening, you
don't need it and it will rust.
"PucIdle the grout quick while it is still wet-
don't wait.
"Don't bother to tie the bars, you jiggle then
too eunuch, just lay then in."
After a short while one of the contractor's
forenoon said: "But those are all things that
will help us save money; we have a Jump sun
contract!" After teat he was very cooperative
and helpful ant] Oracle constructive suggestions
himself.
E CONOMY OF REINFORCING WALLS
It is recognized that steel reinforcing antis
strengths to walls, particularly with regard to
buckling tendencies. This is recognized to a
certain degree in the Uniform Building Cocle
where the H/D ratio permitted for unrein-
forced bearing walls is 20, but for reinforced
walls the H/D may safeIv be increased to 25.
40
The additional strength is also recognized in
'non-bearing walls' in which the limitation
for H/D is Z0 for unreinforced walls but is 30
for reinforced walls.
An exan~ple of the practical result of this
additional value wouIc! be for a story height of
20 feet. Obviously it would be necessary to
use a wall thickness of 12 inches for unrein-
forcecT n~asonr,:: but the grouted rcinforcecT ~na-
sonry couIcT be ~ inches thin!
The unreinforced wall would require 50:O
snore brick and labor and would add 50 ~
snore weight to be carried by the supporting
structure. The foundation would 1lave to sup-
port the additional wall weight' the additional
structure weight and its own consequent acidi-
tional weight.
Also, of course, by a little exercise of in~agi-
nation it Night be possible to eliminate much
of the supporting structure, incorporating it
within the reinforcing and strength of the
REM.
BOND BEA~r
The "Bond Bean" is another element that
can be built into the masonry effectively. The
masons build to the bond bean area and con-
tinue right on through, placing the reinforcing
as they go. This is as opposed to cletailLs which
too frequently require that the masons stop
when they cone to the bond bean area. Then
carpenters cone in to build forms, steed need
to place reinforcing, concrete men to pour the
cleans, carpenters to strip and the masons to
return and continue with the briclkworl; all
of which makes the hair of the superintendent
charged with the coordination and cost of con-
struction turn grey.
Bond beans of REM were used efl ec-
t~velv; on the P. G. & E. Contra Costa Steam
Plant, a building some 800' long, 450' wide
ancT 90' high. (Described in greater cletai] in
ASCE Separate No. 347, No. 540 and an arti-
cle in Engineering News-Record, July; 5,
1951.) Tllis plant was designed for a higher
assumed seismic coefficient than generally con
sidered adequate. In spite of the high design
lateral force, and the 27-foot spans, the bond
beans were of REM, as were tile lligl;l ele- sonry units.
relents between tile "slotted" winclows. Allis
enabled tee masonry construction to proceed
economically without interruption.
As mentioned before, this brick building is
some 800' long and it is to be noted that there
are no visible cracks in the front, rear, or inter
~ncdiate walls, aTtl~ougl~ there are cracks in
the concrete base portion at about 9 foot
centers.
DESIGN
The structural design theory for REM is
identical to the design theory for reinforced
concrete, except teat certain different nu~neri-
cal values are involvecI. Although the clesign is
so similar to our familiar reinforced concrete
design, certain portions are discussed here for
greater clarity. For example the basic assun~p-
tions are:
I. The materials are stressec] within the elastic
limits so Hooke's Law applies, i.e., "stress
proportional to strain."
7. Plane sections before bending are assumed
to remain plane after benching.
3. Tension in the masonry is neglected (ex-
cept for unreinforced masonry portions).
4. Bond is developec] between stecT and ~na
On tile basis of these assumptions, which
result in rather conservative structures, tile
following approximate forn~ula may be used.
M (steel) /s A8f,~
M (masonry) fix by'
6
Formulae can be derived and set up in form
similar to those for concrete for "exact" solu-
tions' e. g., clb' M/K, and saline procedures
foIlowect including:
V l.:L -
bj] it- ojU
Although the design of RBM is basically
identical to tile design of reinforced concrete'
the actual RBM cletaiTs Night tax the in-
genuity of some designers. He does not 1lave
quite tile freedom of placen~ent that he 1las
in reinforced concrete. He must recognize arid
visualize flow the structure will be built by
bricklayers placing nodular units in a definite
pattern. He always keeps in Nina, of course,
tile basic factor of tying all parts of tile struc-
ture together. As in otter architectural design,
_
TABLE OF STRESSES (Assume form & f'c = 2000 psi)
Types Of Stress | RBM
Compressed Flexural
Axial
Bearing
Shear no web reinf.
Shear with web reinf.
Bond, Def. bars
Modulus of Elasticity
Steel, tension
fin = .33 f m 670
fm = .16 f m 320
fm = 25 f rr 500
vm 50
v 150
um = 160
Eon = 1000 f'm
18,000 psi
Reinforced Concrete
f =.45900
fc=.18360
fc=.25500
vc= .0360
v =.12240
uc=.lO200
Em= 1000
8,000 psi
41
it is imperative that tile designer keep clearly
in ninth and execute completely a compre-
hensive scheme of franking to resist the loads.
For example. a load on a slab is carried to
beans which are carried to girders Chicle are
carried on columns, which are carried by foun-
dation pads.
All elements of that scheme must be satis-
factorilv checked that no one little link in the
chain will be overstressed, or overlooked. It
Piglet be e~npl~asized here that the amount of
material is not nearly as important as its
proper placement. As on Marilyn Monroe,
the amount of material is not as important as
is the proper distribution in the right places.
Another item of growing popular concern is
consideration of blast resistant design. The
primary consideration in masonry structures
is ease of placement of reinforcing to resist
the very high loacling assumptions, and free-
clo~n in providing for tying all parts into an in-
tegral structure, one that will 'hang together."
An RBM wall designecl for blast resistance
is sl~own in the figure below. As can be seen
this wall is heavily reinforced and "soaps?, or
split brick are used so the reinforcing may be
placed nearer tile outside surfaces.
~.. A, . . ~
VERTICAL LObIGIlUDIWAL SECTION AND ELEVATION
2 ~ 0 o c .
RBM BLAST RESISTANT WALL
~2
It Night be well for the structural designer
of any plant to check our financial tax struc-
ture and the benefits of fast ' write-off" that
may be utilized for plants designed to resist
atomic blast.
USES 0E RB)/]
Following are some examples of the freeclon~
of expression in this n~ecliu~n. The list is mere,
to show songs different types of examples of
structures. Some are economical solutions to
simple problems and some are to illustrate and
e~npl~asize the principle that one need not be
bound to simple rectangles when building with
bricl:. Some are simple conventional solutions
and some are unusual.
Proof of the a(laptabiTity of RBM would be
shown by tee long list of structures in which
that type of construction has been successfulIv
J J
usec! during the past 30 or snore years. Space
does not permit listing then but they include
large industrial and co~nn~ercial builclings
(warehouses, power plants, stores and facto-
ries ), public schools, college and university
l~uiT(lings, hospitals, VA Hospital in Los An-
geles, churches, public buildings, resiclential
buildings and such special structures as stor-
age bins (circular or rectangular), highway
bridges, bleachers, etc. Even in structures not
requiring design against lateral forces, RBM
lintels are being user} Core and more by many
architectural and engineering offices. Also bear-
ing walls are reinforced because of the econ-
on~v of masonry material and labor.
A complete listing of all structures utilizing
RBM would show its versatility and accept-
ance by engineers anti architects.
The sim#Ze ZinteZ can be eFectiveIv built witty
reinforcing imbedded in the joint. This is as
opposed to the cost and inconvenience of steed
lintels and shelf angles. Not only is the RBM
J lintel less costIv than structural steel, but the
hazard of corrosion with consequent cracking,
of masonry is reduced. In adclition REM elin~-
inates the neec! for maintenance painting.
Also fire hazard is reduced because the reinforc-
ing of the IBM lintel has suitable anc] ade-
quate cover for fire protection.
An example of an unusual use of brick is
shown in the photograph of the garden bench.
it implicates a certain freeclon~ in the use of tee
nasonr;; diFering front the conventional brick
paving or brick walls. Due to its rather unbe-
lievable shape (i.e. cantileverecT brick) it has
presenter! a challenge and has been severely
tested by groups of men at a stag barbecue.
Alley ju~npecl up and clown on the outer edge
to see if by singing ancT jumping in unison they
couIcI break the brick cantilever seat. The only
Manage so far was one skinned shin clue to a
slight unsteadiness of one tester.
GARDEN BENCH
Originally the bench hac] been designed for
the brick to be placed "flat", 2~/~" thick rather
than 4" thick. Since the owner, Lowever, could
not overcome his psychological block that brick
is intended only for bearing and not for canti-
lex;ers, he wouIc! rather have it heavier. This
reaction is a senate example of the need for i~n-
agination in design ant! for sound public eciu-
cation in this matter. The best education of
course is physical example, and we need n~ore
Acorn derring-clot
Another example of the eFective use of rein
PALO ALTO CITY HALL LOBBY
forced brick is the curved wall at the encl of the
Palo Alto City Hall lobby. This is a reinforced
grouter! wall `'cantilevered" above a concrete
floor, receiving no lateral support at the top,
anc] over 10 feet high. However, by curving the
wall we not only achieve a clesirecT dramatic
efl ect in the lobby but provide stability similar
to the stability cle~nonstrated in a serpentine
single thickness brick wall on Thomas JefFer-
son's estate, built in the 1700's. Proper use of
shape is the factor notating Jefferson's serpen-
tine wall so effective.
CHIMNEYS
CI~i~nneys can be constructed rather eco-
no~nically of REM. Chimney design is dis-
cussecl in excellent articles in the July and Au-
gust issues of "Masonry Builder, and also in
SCPT Technical Notes of April and March
1955, Vol. 6, No. 3 and No. 4. Another good
design guicle, and one which inclucles not only
stress due to wind and weight but also due to
temperature, is the ACT Standarcl Specification
43
LIGHT STANDARD
This effect is achieved by threading a con-
crete prestressin~ rod through the draw holes
of the brick. It illustrates a large and little ex-
plored field. There have been some examples
of ``stressed'' masonry like 'CStresscrete', which
uses stressing rods in concrete block panels, but
there has been no very great application of the
principle to masonry.
for Design of Reinforced Concrete Chimneys,
ACT ;0~-54. Economy of seismic design is dis-
cussec3 in Dr. Housner's paper published in
ACT, 19;6.
merely of draft consideration and stress but,
due to our increasing concentration of in-
dustry, of selecting the most economical con~-
binations of height and top diameter (since
top I.D. establishes flue gas clischarge velocity)
for a desired reduction of the concentration of
noxious flue gas discharge. Tile interrelated
cost factors are, of course:
Construction cost increase with height in-
crease.
Construction cost increase with top clian~-
eter increase.
Pumping or fan cost decrease with height
increase. (Draft gain.)
Pumping cost decrease with top diameter
increase.
Dilution gain with height increase and con-
centration increase with top diameter increase.
Given the solution to the above, frequently
manacle more interesting ancT complex by earth-
quake considerations, the engineer may find
an economical solution in REM, especially in
the lower stacks somewhere under 200'. Any
desired diameter, thickness and taper of cliam-
eter or thickness can be achieved easily. The
more modern plants discharge gases at rela-
tively low temperatures so separate linings to
resist extremely high temperatures are not re-
quired. Frequently the interior wythe can be
constructed of hard burned clay brick. The va-
riation in thickness that is required for great-
est economy is easily achieved by varying the
number of wythes and the thickness of the col-
lar joint. A simplification of the running bone]
was used effectively some time ago to provi(le
for the variation in circumference, or length
of course. Tile Cottons of the courses was
started with some wedge shaped pieces and
varying bed joints so that the courses were con-
tinuous "spirals" round and round without
need for cutting brick to maintain "bond" in
The proper sizing of stacks is a problem, not tile coursing. Then to speed production a dou
44
REINFORCED BRICK WALL
Strikino color and te.xt,~re. e{~.~.ts can be achieved by using,. different brick in a single wall.
ble pitch "screw thread" was used. Two brick-
layers could work simultaneously on a wythe,
tee faster one of course catching up to tile
slower one. The contest was obvious, up on a
stage in full view of the entire project, and the
production was quite high in quantity as in ele-
vation. Some said that the "screw" bond ar-
rangen~ent was quite appropriately named.
C ONCLUSION
\~:e Lave describect the details, advantages,
and disadvantages of RBM. Although RBM
was developed initially in the west to meet a
need for an economical earthquake resistant
construction, it has certain inherent qualities
making it effective in any area. As a conse-
quence it may make the use of masonry fea
sible and more desirable than some other mate-
rial in many instances. Furthermore no area is
entirely free from earthquakes; some of the
strongest known have occurred in the east. It
nigllt therefore be well to take advantage of
RBM's inherent safety factor.
r n
0 sung up:
RBM is the technique of laying exterior and
interior wythes of masonry with a grout collar
joint in which reinforcement is placed.
It provides masonry surfaces of elements of
(lifFerent heights, types and coursing, all incor-
porated into a homogeneous structure.
It has an adaptability and freedom of expres-
sion which could be snore fully realized.
Design theory is iclenticalL to reinforced con-
crete design theory.
45
Validity of tile principles and tlleor~- slave
been establisl~ed by test.
It leas a tremendous factor of safety over per
J
witted clesign values.
It is subject to seine typical masonry clisad- went
vantages, namely, modular restrictions of size
or placen~ent, and sensitivity to l~un~an work-
~nansl~ip. It is new ant! masons nest be trained
in slightly different techniques.
It leas several advantages, for instance:
An ageless ancT warns beauty, wills intcrest-
ing texture ancI pattern.
~ relatively low cost of placement.
An elimination of certain Duncan equation
factors.
46
low ~naintenancc cost.
Excellent resistance to cracking and dider-
ential settlement.
finish wall that serves as a structural ele
:Eligl~ ea Nil quake resistance.
Good atomic blast resistance.
Good wcatl~er resistance.
Allis discussion will, ~ lope, help enrich the
vocabulary of the architect and engineer who
seeks full, free, uninhibited expression of Lois
creative imagination as well as function. It may
also provicle food for tl~ougllt for tl~ose Also
seek econo~n~, better builcTings at lover cost.
Cavity, Veneer
and Face-Beaded Walls
M R S H ~ A R Our next shaker is Mr.
Stalker O. Cain of the distinguished New York
architectural jr?n of iMcKim. Mead ~ White,
where he is a farther. Mr. Cain has a Bachelor
of Architecture degree from Western Reserve
University' a Master of Fine Arts fro no Prince-
ton, and is a Fellow of the American Academy
in Ronnie. A 1nenzber of the American Institute
of Architects, he is on the Executive Commit
OUR continuing experiences with Tow-cost
dormitories led us to the cleveloprnent, to-
gether with the firm of Severud-Elstad
Krueger. and Edn~und J. Rappoli, builder, of
the system known to many of you as the "edge-
forn~" method of pre-cast concrete construc-
tion. It involves the mass production of the
vertical components of a building ~ exterior
;valIs, corridor walls and partitions) ancT link
Walker 0. Cain
7\1cKi~n. Mead & N(hite.
New York. N. Y.
tee of the New York Chatter. He is also Vice
President of the Architectural League of New
York City and a Trustee of the American
Academy in Ronnie.
Fir. Cain's office has' over the past years,
done some particular work in cavity wall con-
structio1~, which he wiZ~ speak to you about.
He has been asked as well to address himself to
subjects of veneer ant! face-bon(le(1 walls.
ing them by poured floor stabs. The structural
design is such that columns and beans are
virtually elin~inatecl frown those parts of the
structure where the system is used; more con-
~entional construction being Finitely to rooms
such as lounges and dining rooms requiring
longer spans.
Without dwelling on the techniques of
mass production and the assembly of con~-
47
portents at this particular meeting, it can be
sai
stantly throughout construction history. When
we read that Augustus "found Blonde a city of
brick and left it a city of marble," we acknowI-
edge it a feat even in marble veneer. Although
the technique of applying stone sheathing has
changer! remarkably little front that tinge to
this, there has been a notable change in de-
sign and construction of the building frame
itself. Where the Romans applier! veneer to
bearing wall construction, usually of massive
brick and concrete, we apply it to a skeleton
France. The difference between sheathing the
Pantheon on one hancI, and the U. N. buiTd-
ing on the other, are essentially those inherent
in the difference in building frames. We have
to clear with n~oven~ent of the material itself
as well as rnove~nent in the frame, and taken
together these are analog the most critical
problems to be solved. Experiments are al-
ways being undertaken, and bonding patterns
are as changeable in fashion as ladies' hats.
The current efforts lean toward thinner and
thinner veneers, less emphasis on fully bonded
walls except where more permanent or monu-
mental structures are involved, and attempts
to combine thin stones with metal Frances and
panels.
Masonry construction has in the past solved
exterior wall problems in a superior fashion
because of its great strength, (lurability, re-
sistance to weather and fire, dimensional stabil-
ity, thermal transmission ant] its characteristic
graceful weathering.
In view of current trends it may well be that
beauty in old age will emerge as its most valu-
able quality. Strength itself is less important
because stone is more likely to be supported
than supporting. Fire resistance and thermal
transmission may be less of a consideration
under current pressures on cocles to revise
downward present fire resistant ratings for ex-
terior walls. However, weathering and dimen-
sional stability will be its prime attraction in
any technical development likely to take place.
Contemporary design makes heavy clemands
for crisp. taut, clean surfaces. With proper
selection of stone and correct detailing, ma-
sonrv still affords the architect maximum as-
surance that a design will retain its original
character for the life of the building.
49
