5et. Slte~i:11 flll:llit" Itl-i~l( 111:ISftlll-,' 1IIIIItist"I-,' :llt:lleflllellt IIftllSes Itllilt ill S\\'itzel-I:llltI.

H. Lechner, Ziege/strasse, Switzerland

Preparatory Planning

The building costs of multistory apartment houses are proportionately higher in Switzerland than those of two· to five·story houses. (Due to using hlgh·grade bricks and mortar and to hlgher wages as compared to those for standard·grade masonry, the special-quality BS brickwork costs 15 percent more. The wages are hlgher because the laying must be done more carefully and consequently takes longer. An elevator for up to five stories is considerably cheaper in Switzerland than ane for 8 to 20 stories. Sanitary installations, toa, are more expensive- if only beca use the pipes have to be bigger than in lower houses. And so on ... )

The project designer must therefore economize wherever feasible . Any engineer, on getting his first order to design a residential building, is Jikely to give preference to reinforced or steel concrete. On looking into the econontic aspect , however, and on comparing high·grade, special·quality brick masonry with other materiais, he will soon reaUze that brickwork offers the best for the price. Such a wall is simultaneously load· bearing and heat-insulating. Skeleton structures require an expensive load·bearing system and a fllling of masonry between the supports, and each costs nearly as much as the load·bearing, special·quality masonry of a brickwork building. A cellular wall system using reinforced concrete is the most expensive way af building, since a reinforced concrete wall costs 30 percent more than a brick wall of the same thickness.

Thls only applies, however, to ground plans with small spans of 3 m. to 4.5 m. (9.84 ft. to 14.75 fI.) and provided ali the walls assume the loads as ceUs do , as is generally the case in hlgh·rise apartment buildings.

When developing the floor plan of an apartment, the architect must take pains to forro cells with the Uving and

Figure 50·1. Ground plan of 18·storey ''Hirzenback'' building. Zurich.

416

other rooms. As a result , the loads will be evenly distribul,d so that the walls may be relatively thin. For smaUer sP'ce;' 5uch as bathrooms and closets, nonload-bearing wal1s are qUI e adequate. (Note Figure 50·I). . ali

In floor plans for paraUel partitions, the maxlmum WOI

spacing must not exceed 4.5 m. or 5 m. (14.75 fI. or 16.4

ing,

ted ces. uite

.. ali ft.)

Brick Masonry Apartment House in Switzer/and 417

1475'-16.40' 14,75'-16.40' 11,.75'-16.40'

114.50- 500 11450-500 II 450- SILILt-

.. -----

Figure 50·2. Diagram of plan for paral/el partitions.

speei.1 form work of sleel or plywood as large as whole walls, and sinee lhe eonerele surfaee a1lows lhe wallpaper lo be hung immedialely, reinforeed eonerele is eheaper from lhe Iwenlielh floor up, lhe expensive form work having been amorlized by Ihen.

Iwo years ago I had 22· lo 25·slory houses eonlaining 416 aparlmenls in ali lo build for lhe eity of Zurieh, using lhe Iype of eonslruelion wilh sim pie parallel parlilioning walls. On comparing costs, the reinforced concrete structural system was given preference for the previously mentioned economic reasons.

Many years' researeh work by Professor Paul Haller of lhe Federal Malerial Iesting Institute at Dubendorf- Zurieh, with lhe eooperation of lhe Swiss briek induslry, resulted in produeing a speeial·quality briek (grade BS) whieh resists exeeptionally heavy slresses.

lhe standard tesl of lhe speeial BS grade musl arrive at the following values2:

s Speeifie absorptive eapaeity g'/dm2 x mino t, s Seatter in g'/dm2 x mino

-;;: 17 ±5

Figure 50·3. Example of interior wal/ detai/s. 1/4, 1/2, 3/4, and l/l size bricks.

beeause here lhe stiffening effeet of lhe inlerseeting walls is Jacking, and lhe briekwork would otherwise have lo be 100

thick. It goes wilhout saying thal lhe walls may be spaeed furlher aparl- but on1y aI lhe expense of lhieker walls. (See Figure 50·2.)

In elaborating the aparlmenl floor plans, the arehiteel must be guided by lhe briek dimensions when delermining walI lengths and pillars. As a rule, lhe butt joinls may be I lo I· 1.2 em. (3/8" lo 1/2") Df maximum 1.5 em. (5/8"). Brieks being produeed in 1/4, 1/2, and 3/4 sizes, the arehileel has plenly of leeway. (Nole Figure 50·3 .)

Seleetion of MateriaIs, Statie Analysis, Dimensioning

The lerm "multislory" applies lo buildings of at least eighl floors . In Swilzerland , lhe limil for briek masonry probably lies around 20 stories .

Obvious)y , it is not a technical problem to raise brickwork higher Ihan 20 slories. 1t is rather for eeonomy's sake. Wilh

{l s Crushing slrenglh in kg'/em2 (1.026 t. per sq. ft.)

t,{ls Seatter in pereenl Lo Shape of perforation: round, triangular,

reelangular, rhombie Pereenlage of lolal area

AI Dimensional alJowanees: AM - maximum deviation af the single va]ue

fram the roeao value in percent length and widlh heighl

AS - maximum deviation of lhe mean from the design value in mm. (0.039") length widlh height

value

=400' ± 15

15 to 35

± I ± 1.5

± 4 ± 2.5 ± 2

*The strcnf:,1.h of the 18-cm. bricks must correspondingly be equal to 440/cm ' (451 t. persq.ft.)

418 Designing, Engineering, and Constructing with Masonry Products

EL Planeness of bearing faces in mm. (average ealipered heighl) 'S 0.07 bs

R Craeking no eraeks KK Expanding grains of quiek lime (deerease in

tensile strength and resistance to cracking in pereenl) 'S 10

Mortar

Bonding agenls (portland eemenl) for preparing lhe brick­work mortar musl meel lhe SIA (Swiss Assoeialion of Engineers and Arehileels) Slandard 115 "Slandards for Bonding Agenls for Buildings"3

The natural sand used must not contain more thao 5 pereenl of soft wealhered grains4 Expanding or waler-soluble eomponenl parIs are harmfu!. The sulphale eonlenl musl nol exeeed 0.1 pereenl by weighl of S03' And lo prevenI melaI corrosion , the chloride content must not exceed 0.05 percent by weighl of CI.

In a sedimenlalion lesl after lhe SIA melhod , briekwork subjeel lo heavy slresses andjor exposure lo lhe wealher should deposil a fine layer of maximum 2 mm. (0.078 in.). Sand mixed aecording lo lhe grain·size curves of SIA Slandard 162, and screenings 100, as a rule, make a good qualily morlar. Sands laeking lhe finesl grains (Iess Ihan 0.12 mm.) bul eonlaining a 101 of grains belween 0.2 and I mm. (0.0078" and 0.039") in size, produce a porous morlar wilh liltle resistance to crushing. The largest grain sue must not exceed one-half lhe joinl Ihiekness.

The mixing waler should be above 8° C and musl nol contaio any injurious substances, in particular none af 3n

organie nalure. (Oxidizabilily < 100 mg. KMn04 per liler.) The dose of bonding agenls is speeified in kg. per m3 of

prepared mortar. The dose for BS brickwork is 350 lo 400 kg. per m3 of ready-Io-use morlar (0.30 lo 0.34 t. per eu.yd.).

The morlar musl be lesled as lo slrenglh in advanee as well as during conslruclion aI leasl onee for every slory. For BS briekwork the mort"r slrenglh musl reach ~m28 = 200 kg./cm2 (205 t. per sq.ft.).

SIA Slandards 1606 and revised edilion (in preparalion) give lhe useful and lhe wind loads and also lhe assumed seismic stresses. For residential buildings , the useful loads aTe normally 200 kg/m2 (0.02 t. per sq.ft.), lhe wind loads varying wilh lhe shape of lhe building. In exlreme cases model lesls must be made in a wind tunnel. As to seismic effects, the structures have to be calculatcd for a horizontal acceleration of g/50, as a rule. In regions parlieularly subjecl lo earlh­quakes, the authorities may specify an allowance for an acceleralion b equal lo g/20. Wind and seismie slresses are nol apt to occur simul taneously.

Slalie Analysis

General. The slalieal ealculalions mllsl resull in lhe safely of the whole structure and of its individual parts. as specified in SIA Slandard 160 "for lhe assumed loads and for lhe putling into operation and the supervision of the structures".7 Thcy will be based on Iried and proved melhods of ealeulalion and

Table 50-1 (a' + b') Speeified Minimum Load Capacity of BS (Speeial-Qualily)

Brickwork in kgjem 2 (1.026 I. per sq. fI.); Age 28 Days

Cernent bond

Kind of

brickwork

Thickness

ofwaU

Slendemess

fatio PC 350 to 400 kgJm 3

One-briek masonry

Bonded masonry

d em

12

15

18

25

25

30,32, 38

Ik{d

8

26 8

21 8

17.5 8

15 8

15 8

m :::::: o m =

250 135

160 55 210 135

160 75 190 135

160 95 200 135

170 100 155 1 15

135 90 155 115

wi str lo;

be WI o, bo sli SI

MI be of sI,

" ta

OI

'n r.) of 'g.

ell as 00

n) ed Ire ng 'Is he

'n h· In

01

of in ng ey nd

Brick Masonry Apartment House in Switzerland 419

Table 50·2

Kind af Masonry

Thickness Compressive Special-quality ofwaU stress and BS masonry

Onc·brick masonry

Bonded masonry

em.

12 12 15 15 18 + 25 18 + 25

25,30 32,38

in.

4.73 4.73 5.91 5.91 7.09 + 9.85 7.09 + 9.85

9.85,12 12.6, 15

will allow for lhe aclual performance of the buildings. The slresS analyses must reveal the effects af each hypothetical load separalely .

The stability of buildings and Iheir component parts must be assured by ceilings, stiffening partitions, and olher devices. When calculating and planning masonry, the inevitable sec­ondary effecls of lemperature and the shrinkage of cement­bonded materiais must be allowed for, in parlicular dynamic slresses from strect trafrie and other causes. as spccified by SIA Standard 160.

lIodulus of Elasticity. Should no values for the masonry used be available , the following approximative values of the moduli of elasticity may serve to determine deformations af artificial stone masonry due to temporary loads.

8rick masonry with Portland cement

8 ~M E = 360 000 ~ M+400 (50·1)

Vertical Load in the Wall Plane. The mean normal stress, calculated from the unfavorable overlapping of ali the sim ui· taneously acting factors , is determinative. Disregarding per­forations and slots, the wall section is counted as cross­sectional surf ace.

The masonry must not be expectcd to resist any tensile stresses vertical to lhe bed joints.

The measure of eccentricity m of lhe axial force is to be calculatcd on the basis of lhe moduli of elasticity of the building materiais, simplifying hypolhcses being allowable. By no means must lhe eccentricity exceed double the kern width.

In lieu of the Icngth subjcct lo buckling. the story height is entercd in the calculation. By allowing heavier compressive stresses for abutting brickwork walls and for T-shaped or cruciform parts of walls, their stiffening effect is accounted ror. Concentratcd loads may be distribuled in undisturbed

abscissae section m '" O m = 1/2 m = 1 m = lVz m=2

a5 50 40 30 20 10 A 55 45 36 28 16 a5 44 36 30 20 lO A 55 45 36 28 16 a5 40 34 30 20 10 A 55 45 36 28 16

a5 34 29 25 16 6 A 55 45 36 28 16

parts of the masonry under 60° to the horizontal. The load distribution must be judged according to the performance of the whole supporting structure.

Horizontal Loads Perpendicular to the Wall Plane9 Bending­tensile stresses may be borne parallel to the bed joints, provided the butt joints are adequately overlapped, and the load on the wall is vertical. Reinforced masonry with steel inserts in the bed joints is calculated Iike reinforced concrete , disrcgarding the tensile strength of the masonry.

The stresses in masonry and steel can be determined with the valence number:

Es n =-= 20

EM (50-2)

The specifications given in SIA Standard 162 "Calculation and execution of concrete and reinforced concrete work" are to be adhered to in the sense of lhe word. 10

Calculation and Permissible Stressesll

Table 50-2 shows the stresses permissible for BS special· quality brick masonry with Portland cement mortar PC 350 to 400 kg. per m3 (0.30 to 0.34 t. per cu.yd.).

In arder to determine the eccentricity of the loads, ali the expected static conditions must be taken into consideration, such as: torsions, unequal deformations, restraints , shifting of the supports, etc. The eccentricity of the points of application of normal forces in pillars and walls can be calculated from the momen!s at the top in the double cross (see Figure 50-4) with a flexible connection, assuming bilateral and alternate appli­cation of the useful load. Even if loads are applied more unfavorably , the permissible stress must not be exceeded. By halving lhe carne r angles, the weight of the ceilings and the loads evenly applied thereto may be divided into three- ar

420 Designing, Engineering, and Conslrncting with Masonry Producls

h h C;(, --11, (;('1.= -~ t, l7.

M1 =-1 m1 e, - PI k

1 .. (;(1 + CX2 ""'" r

MI '2lf(I+r)-tir M1. - '2.1-?{I+rFl;zr

JrEr ~=-

JsEs

Mz. e-z- -P1.

Figure 50-4. Calculalion syslem for walls!4

p

<>2 -=m1. k

four-cornered load parts and lhen reckoned with as a uniform Ioad.

Compressive and Buckling Stresses

Structural masonry rnade af bricks meeting the specifi · cations for speciaI-quality BS brickwork (standard test 2 and the required minimum Ioad-bearing capacity sub a' +b' 5) may be dimensioned with the permissible mcan stresses af the Table 50_2 11 (permissible st resses for speciaI-quality BS brick masonry). (Margin of safely Y ; approximalely S.) They are characterized by a linear dimillution to the theoretical border-hnc slenderness A where lhe permissible strcss becomes zero (see Figure 50·5).

In lhe Table 50-2 1 I the basic values as and A are given for near-concentric and for equ ilaterally eccentric loading (m=O, 1/2, I , 1·1/2, 2). These values enable one to find the permissible mcan normal stresses from the diagram above.

The classes af masonry corresponding to a5 must not be exceeded under single Ioad.

Unequally and Crossed Eccentric Attack of Load 16

When the load at tack 00 masonry of artificial stones is unequally and/ar crossed eccentricaI, the buckling stress oak will be mulliplied by lhe reduction faclor a:

I[m~ ] a; '2 oak (1 +1/) + (I - 0.1 m) (I - 1/) (50-4)

mOk ; permissible slress for a slenderness ratio of Ik/ d and an eccentricity fatio m:

H [:=1; -mI - +1 ( I' O to - I crossed eccentricily I --- 0 -k 1/ m . O to + I equilateral eccenlricity

ml I rnl I -;;: I m I (50-5)

Js P1

h

Jr M( h

J~

J

l( h d'

d'Zul. Õs

l 5 A l 'k/d

~1~------------~~--------------f,~

Figure 50-5. Diagram for finding lhe akzul

from lhe values õ, and A after Table 50-2! 3

L- or T-Shaped or Cruciform Wall Sections17

For 1.- or T-shaped wall seclions and for seclions pl,c<d crosswise the slenderness fatio lk/i is calculated from th! minimum moment af inertia (maio axis), for which. purpon the permissible stress azul is taken [rom the dJagram corresponding to the quality and strength of lhe masonry·

~;~ 'l2' i d '\I ".

(50-6)

r e 01 At the distance 12d, measured from the inner In Ih'

intersection , lhe wall seclions may only be Ioadcd w.lh I or Permissible stress 0k. Le. irrespective af any stiffening ef[ec ..;>

.' lO"" the angular wal1 sections. The reduction in the tran51tlon

12 0. ar,

Brick Masonry Apartment House in Switzer/and 421

y

diaqram of pelrmiis!>ii:?l"

buckling limits cSkzul

permi ..... ible sl.-,,!>!> for lI( I d

d'

l-I I I

Figure 50-6. Diagram of the reduction in the transition zone of 12d approximate/y after the cos function between azul and Gkzu1 '

Table 50-3

i\ ia Length of wall sel:tiun

2d 4d 6d

1.0 1.00 1.00 1.00 0.8 0.99 0.98 0.96 0.6 0.99 0.97 0.93 0.4 0.98 0.95 0.89 0.2 0.98 0.93 0.85

12d is effected approximately after the cos funclion between õ,ul and ukzul (See Figure 50-6). Reduction value <p (= cos -area) may be taken from Table 50-3.

The reduced permissible stress to be entered ioto the calculation for ooe wall section:

- -ar = I.{) x a (50-7)

The pennissible stress uk governs the wall sections > 12d. When verifying the capacity of the walls to resist seismic

stresses, the permissible axial and buckling stresses may be raised by 50 percen!.

Planning Data

For every slory the architect will draw layer plans showing flawless brickwork bonds and depths of bonding-in recesses for plumbing, ele. Subsequent pointing is not admissible. Hard bricks like the special-quality Does are brittle and have more residual stresses than bricks of less compressive strength ; they

8d IOd 12d

1.00 1.00 1.00 0.94 0.92 0.90 0.88 0.84 0.80 0.82 0.76 0.70 0.76 0.68 0.60

are apt to crack in odd places, thereby weakening the brickwork. Consequently , only bricks factory-made in 1/4,1 /2 or 3/4 lengths may be used besides fulllengths. The layer plans must also give the bed and the butt joints , the former being 10 mm. thick, as a rule , the latter 12 mm. (0.47 in.) at the mos!.

To obviate cracks due to constraining stresses, the engineer will make a point of only using material having one and the same modulus of elasticity throughout a single ground plan. Should he, however, be forced to provide for a pillar of reinforced concrete, for example, he will dimension it in such a way as to ensure its deformability being analogous to that of the brick masonry. A ttention must a1so be paid to having the existing compressive stresses in the masonry be approximately the same in ali the walls.

Furthermore, the walls in each succeeding story are to rise concentrically abovc those below in order to avoid additional eccentricities.

Specifications regarding quality and execution covering bricks, mortar and quality of masonry , are to appear on each layer plan. (Note Figure 50-7)

422

LAYER

LAYER

Designing. Engineering. and Constructing with Masonry Products

0.492' 0.394'

lZl M BRICK

181 1;2 BRICK

fi \.i SRICK

VIEW DF INTERIOR WALL 15 em.

,. , ';LlNTEL , ,

I • I I 6.76 2.06 3.41 6.01

, 2 .06 ! 63 ! 104 ! (::I 183

CEILlNG AS AS AS AS A AS AS AS

S A CEILlNG

1. 672'

! 51 I

'li'lJij 1111111111 11111 ~IIIIIIII ! I : I :1111 n~ LAYER S 25 25 25 ~ 25 Z, 25.. _ -r-- IflTV lr- 1 1'1 1 t

ílJ]i'I'I'IIIII'1111 ~ 11'1 1111'1'1 11'1 1 ~~ LAYER A LRECESS IN WALL OVERLAPPING min 6 em Rl

I 1 '2 I 6 I I I I 1= 0.0328 1~ 0.0361 1 _ 0.0394 1_ 0.0525 6_0.197 7. Q23 12.0.394 15= 0.49' lB~ 0.591' 25= 0.82' 38= 1.25'

l [I I I L

INSULATION -J' r INSULATION-' l-r

7 I- 18 7 r 18 LAYER S 11-LAYER A

I-- '- '---

WALLS 18 em.

Figure 50-7. Layer plan.

-I ... 1- ::J

f1I r.

• ... ;;t

111 111

111 ::l ..., """I

r.: õ;1

f1I 111

r- I .. ::]

1- ::1

Figure 50·9. "Zentrum," Wettingen, 19 stories. Constructed: 1963·1965. Fac,ades: prefabricated concrete. Interior walls: 0.492 ft . - 0.591 ft. (brick).

.11

1

If ~ ~ ~

~

-~ ~ ..-'" I ..-

t1' .. "

~:;1

~

, r' .r1 -,

423

Figure 50·8. "Hirzenback," Zurich, 18 stories. Constructed: 1956. Facades: 1.25 ft. 1nterior walls: 0.492 ft. - 0.82 ft.

-". ,., r r " r " r r (

" r r r r I I

r .' I rJ

I -r

424 Designing, Engineering, and Constructing with Masonry Products

Construction Superintendence

Supervision

Depending on lhe size of lhe slruelure , one of lhe engineer's responsible superintendents is to constantly check on the sile whelher lhe dala of lhe layer plans are being observed. He also eheeks whelher lhe demanded qualily of lhe masonry meets lhe requirements specificd, particularly in regard lo lhe folIowing values perlaining lo BS masonry.

Permissible devialion from lhe slraighl Iine12 1/800 Devialion from lhe plumb in mm. per 2.5 m. of

heighl (0.039 in. per 8.2 ft.) 3 Deviation of the bed joinls from lhe horizon lal

in mm. per 2.5 m. of lenglh 3.5 Thiekness of lhe bed joinls in mm. (0.39 in. lo

0.47 in.) 10 lo 12

The masons will be provided wilh a1igning poles wilh lhe accurate arrangernent af the joints, and enjoined to lay each layer wilh the lead line. Dropped morlar musl nol be applied, and the mor lar musl have been used up by slopping time.

The superinlendenl will make sure thal only skilled masons are pul on BS jobs. li is a good idea lo give Ihem some preliminaI)' training on a sample wall.

The eonlraelor is responsible for lhe speeified quality of the masonI)' .

Tesling Brieks and Mortar BeCore and During Construetion !3

The morlar will be delermined before hand by lesls ai lhe EMPA Researeh Institute. Three prisms 4 x 4 x 16 em. (1.57 x 1.57 x 6.3 in.) eaeh per slory are tesled after 28 days and must then show a minimum slrenglh of 200 kg. per em2 (205 t. per sq. ft.).

AI eveI)' seeond slory aI leasl len brieks will be lesled as to adherenee lo lhe slandard.

Praetieal Experience

With lhe brieks available from Swiss brickworks, viz.:

. 12x25xI3.5cm., Slzes (4.73" x 9.85" x 5.32")

15 x 25 x 13.5 em. and

(5 .9 1" x 9.85" x 5.32")

18 x 25 x 13.5 em. (7.09" x 9.85" x 5.32") and

the corresponding fractional sizes 1/4, 1/2 and 3/4 which are 6 em. (2.36 in.) , 12 em. (4.73 in.) and 18 em. (7.09 in.), respeclively, il is perfectly possible lo conslruct walls of any length aod pillars of any height.

In the 8-, 10-, 12-,13-,14-, 16-, 17-, and 18-slory buildings I have conslructed of special-qualily bricks, I designed lhe façade walls 39, 32 , 25 and 18 em. (15.37 , 12.6 ,9 .85 and 7.09 in.) lhick, respeclively, and lhe inlerior walls 12, 15 and 25 em. (4.73, 5.9 and 9.85 in.) thick. (Nole Figures 50-8 -

50-12) Of late I have changed over to even Ihinner walls: 18 Or 25 em. for façades wilh ao ex Ira insulaling sheel , and 12 ar 15 em. for lhe inner walls. Facades being lhick mainly fOr heal-insulaling purposes, bul 100 Ihick slalically speaking. thinner walls plus insulation are actually more economical.

I have been occupied wilh mulli-sIOI)' brick buildings fOr 12 yeaIs now, but even in Switzerland, where there are extreme differences in meteorological conditions, [ have thus far detccted practicaUy no cracks Or other damages worth mentioning.

Future Improvemenls

What progress il would mean if research led lo lhe production of an economical plastic mortar enabling a reduclion of lhe joinl Ihicknesses! Then glueing mighl even suffjee. Bul the bricks' surfaces would have lo be absolulely plane and smoolh. It is conceivable thal lhe strenglh of masonI)' could be increased Ihis way. Prefabricaled producl' like Preton, for instance , also have a promising future. But the bonding of lhe walIs where they abuI in lhe corners has nol yet been solved salisfaclorily.

8ricks

B Is

Symbols

Brick Length of brick in em.

rr rr ri C[ rr rr r. r= 1=. r r c: rr ~ rr .-r;r F 'H

Figure 50-/0. ''Holzerhurd, '' Zurich, 18 stories. Constructed: 1965-1966. Façades: reinforced Duriso/, 0.656 ft. - 0.82 fI. Interior walls: 0.492 ft. - 0.591 ft. (brick).

I

5

'.

I

e

e a n y ,f s e II

I w: fi

Brick Masonry Apartment House in Switzerland 425

Figure 50-11. "Sandacker," Neuenhof, 17 stories. Con­structed: 1965-1966. Façades: 0.591 ft. + 0.23 ft. insulation -1.05 ft. Interior walls: 0.492 ft.

bs hs Is/bs/hs AT AM

AS

s

6s

Lo EL

R KK

Breadlh of brick in em. Heighl (Ihickness) of brick in em. Formal of brick in em. Dimensional allowance Maximum devialion of lhe single value from lhe mcan value in per ceot Maximum deviation of the ruean value from the design amount in mm. Specific absorplive capacily after lhe EMPA melhod in g-/dm2 x mino Maximum deviation Df the specific absorptive capacity from the rueao value in go/dm2 x mino Area of perforations in percent Df total area Planeness of lhe bearing faces (mean of caJiper checks laken aI random in mm.) Cracking Expanding grains of quick lime. effecl on tensile strength, and resistance to cracking. Determination af these capacities in teo bricks after 24 hours' cooking. Deplh of brick in em.

Figure 50-12. Detail ofinterior wall (see Figure 50-3)_

Mean value of crushing slrenglh of bricks laken from len single values (breaking load divided by gross area) Grealesl deviation of the single value from the me ao value in per ceot Mean value of crushing slrenglh of brick in kglcm2

Mortar for WaU

~m

PC 350/400

n~m v~m

Brickwork

BS u d dM ~M n~M v~M

Cubic crushing strength of the morta r prisms 4 x 4 x 16 em. Dosage: 350/400 kg. of Portland cemenl per cubic meter Df prepared mortar Standard crushing strength of lhe mortar Crushing strength of the morlar found by testing

Speeial-quaJity briekwork Overlapping of brieks in adjaeenl layers in em. Thiekness of wall Thiekness of parI of wall in briekwork Strenglh of brickwork Standard ntinimum load eapaeity of brickwork Crushing Slrength of briekwork found by tesl­ing

426 Designing, Engineering, and Constrncting with Masonry Products

Statical Symbols

N

L L F

Ik

k e m

5...

EM Es n A

v

oas

Longitudinal force

Radius of gyration i =~J/F' Moment af inertia Gross eross·seetional area (without deduetion of perforations or slots) Length subject to buckling (distanee between the joints, height of stories from axis lo axis) Kern widlh Eccenlrieity of poinl of atlaek of load Measure of eceentrieity m = e/k Ralio of the eecenlricily eoefficienls ml/m at both ends of the wall Modulus of elasticity of the briekwork Modulus of elasticity of lhe sleel Valenee number n = Es/EM Abscissae section of the straighl line of buek· ling Safety faetor (breaking load divided by per· missible load) Pennissible mean normal stress within the

strength limits (lk/d -;;: 5) wilh a near· concentric load Permissible roean normal stress withjn the slrength limils (lk/d -;;: 5) wilh an eeeentric load Pennissible mean normal stress wilhin the

buekling limits (lk/d > 5) with a near· concentric load Permissible mean normal stress witrun the buekling limits (lk/d > 5) with an eceentric load Mean normal stress from permanent load

Permissible bending stress parallel to lhe bed joints Pennissible shearing stress Permissible stress for a given slenderness fatio and a measure af eccentricity taken from the diagram

References

I. "Standard for the Calculation and Exeeulion of Masonry Using Artificial and Natural Stones" SIA Standard 113, Prof. P. Halier, Chairman of Slandards Commission, 1965, p.32.

2. Ibid., Table V, p. 5. 3. "Slandards for Bonding Agenls Used In Building," SIA

Slandard 115 , 1953, Ar!. 14, 15 , pp. 10-12. 4. SIA Slandard 113, pp. 1-2. 5. Ibid., Table I, p. 3. 6. "Slandards for lhe Assuming of Loads, lhe Putting in lo

Operation and lhe Supervision of lhe SITUelures." SIA Slandard 160, 1956, Ar!. 27, p. 20 , Ar!. 20, p. 13·16, revision Ar!. 21 , p. 13.

7. Ibid., pp. 5-28. 8. SIA Slandard 113, pp. 7~. 9. Ibid., p. 8. •

10. "Slandards for lhe Caleulalion and Exeeulion of Concrete and Reinforced Concrete SITUetures ," SIA Slandard 162, 1956, pp. 448.

11. SIA Standard 113, Table X, p. 9. 12. Ibid., Table XVI , p. 13. 13. Ibid., p. 14. 14. Ibid., p.23. 15. lbid. , p.8. 16. Ibid., p. 10. 17. Ibid.