1 . b . 1

DEVELOPMENT DF PREFABRICATED FACING BRICK PANELS

K, FISHER Redland B1'icks Ltd. , Horsham, Sussex, Great Britaú,

B,A , HASELTINE Jenkins & Potter, Consulting Engineers , &ondon, G1'eat B1'itain

DEVEWP''ENT OF PREF4BRICATED PACING BRICK PANELS

The manufacture of prefabricated brickwork panels has

been a topic of interest for some considerable time

amongst brick manufacturers and materia l users in the

const1'uction indust1'y . Following a b1'ief summa1'y of

the va1'ious options available for panel prefab1'i­

cation with an indication of related examples , the

papel' reports observations of t1'ials carried out to

construct and erect a, se1'ies of panels built by trad­

itional methods under, controlled conditions . The

work aimed to provi de an opportunity to simulate the

on-site construction and erection of brick panels

such as would be used in a typical jramed structure.

Four panels were built , comprising two sto1'ey -height

(2 . 6 m) panels , nominally 3. 8 m. long, to reproduce a

typical C01'ner detai l with two spandrel panels along­

side , 1 m. high, 3. 6 m. long o Special b1'icks at the

panel edges provided an aesthetically dis tinctive ex­

pression of the joints . Panels were positioned

.directly on a concrete floor slab and fixed to

columns at each end of the panel. Particular atten­

tion was given to details concerning appearance , di ­

mensional accuracy , handling, fixing and jointing.

The problems encountered in satisfacto1'ily meeting

these r equirements are discussed .

ENTWICKLUNG VON VORGEFERTIGTEN

WANDTAFELN IN FASSADENSTEINEN

Die Herstellung von vorgef ertigten Wandtafeln aus

Ziegeln war lange Zeit beliebtes Diskussionsthema

unter den Zieglern und den Bauunternehmern .

Nach einer ku1'zen Uebersicht übe1' verschiedene

Móglichkeiten von V01'f ertigungen mit Wandtafeln

an Hand Von Beispielen, werden die Autoren be ­

richten über Beobachtungen bei Versuchen, um eine

Reihe Von M2ndtafeln auf herkómmliche Art und

Weise , jedoch unte1' Anleitung , herzustellen .

Vier Wandtafeln wurden gebaut, die zwe i Wandta ­

feln mit einer Stockwerkshóne von 2, 60 m umfassen,

nominal 3, 8 m lang, um eine typische Eckausbildung

mit zwei langseitigen M2ndtafeln von 1 m hoch und

3 , 6 m lang zu reproduzieren . Die Wandtafeln wurden

unmittelbar auf dem Beton -Fussboden angebracht und

auf beiden Seiten an SãUlen be festigt . Besonder e

Aufmerksamkeit galt Einzelheiten, die sich mit dem

Aussehen, de1' Exaktheit und den Abmessungen, dem

Transport , und dem Anbringen und Fugen befassten .

Die FTobleme, die sich hierbei ergaben, werden be ­

spr ochen .

1 . b . 1 - 0

LE DEVELOPPEMENT DES ELEMENTS

PREFABRIQUES EN TERRE CUITE

La préfabrication d 'élements constitués de briques,

fut de tout terrps un sujet de discussion entr>e bri­

quetier>s et entr>epr>eneur>s . Apr>es avoir> passé en r>e­

vue les diver>ses méthodes de fabrication de ces élé­

ments , les auteur>s font quelques obser>vations quant

aux possibilités tr>aditionnelles de constr>Uction

d'éléments et de leur> errploi , en r>espectant toutefois

cer>taines conditions irrposées . L'ouvr>age t~che de

tr>ouver> une méthode qui simuler>ait les conditions r>éel­

les d 'ér>ection et d 'emploi de ce genr>e de panneaux,

tels qu 'ils ser>aient utilisés dans une constr>Uction as­

semblée en squelette et ar>matur>es.

Quatr>e panneaux fUr>ent constr>uits, dont 2 d 'une hauteur>

d 'un étage soit 2,60 m et d 'une longueur> nominale de

3,80 m, deux autr>es r>epr>ésentaient un détail typique

d 'un assemblage en coin et mesUl"aient 1 m de hauteur>

SUl" une longueur> de 3, 60 m. Des briques spéciales

donnaient au coin-même un aspect esthétiquement valable .

Les panneaux fUr>ent appliqués dir>ectement SUl" une sur­

face en béton et attaohés de chaque côté aux colonnes .

Une attention par>ticulier>e fut consacr>ée aux détai ls de

la pr>écision des mesur>es, du tr>anspor>t , de l 'assemblage,

des joints et de l 'esthétique génér>ale. Tous les pr>o­

blemes qui se présenter>ent font l 'objet de disaussions.

UE ONTWIKKELING VAN GEPREFABRICEERDE

BAKSTEENELEMENTEN.

Het maken van gepr>efabr>iceer>de baksteeneZementen is

lange tijd een geliefd diskussieonderwer>p geweest on­

der> steenbakker>s en aannemer>s. M2 een kor>t over>zicht

van de ver>schillende mogelijkheden voor> de fabr>ikage

van baksteenpanelen, met voor>beelden, geven de auteUl"S

enkele obser>Vaties inzake pogingen om op tr>aditionele

wijze , doch onder> gekontr>oleer>de voor>waar>den, slemen­

ten te ver>vaar>digen en te gebr>uiken .

Er> wer>d een poging gedoan wer>fvoorwaar>den te simuler>en

en elementen in te bouwen in een typisch skelet .

Vier> elementen wer>den gebouwd, waar>onder> twee met ver>­

diepingshoogte (2.60 m) , nominaal 3,8 m lang, en een

typisch hoekdetail met twee panelen van 1 m hoog en

3.6 m lang . speciale stenen op de hoeken gaven het ge ­

heel een estetisch verantwoor>d uitzicht . De panelen

wer>den dir>ekt op een betonnen vloer> geplaatst, en op

beide zijden aan de kolommen bevestigd.speciale aan­

dacht wer>d gegeven aan details in ver>band met uitzicht,

nauwkeUl"igheid van de ajmetingen, tr>anspor>t, bevesti­

ging en voegen . De pr>oblemen die hierbij opdoken wor>­

den besproken.

1 . INTRDDUCTIDN

Interest in prefabricated brickwork is by no means new . Early trials were carried out in the U. K. about 40 years ago. and development work was underta ken by a number of brick manufactur e rs in the early 1960's, but few Df the resulting systems have been widely used in the intervening years .

Dverseas there has been a steady increase in the use Df prefabricated panels, notably in the U. S . A. and in Holland . Some European brickmakers hold the opinion that sooner or later, a large proportion of their out­put will be supplied to the construction industry i n prefabricated panel form o

Several major advantages exist for prefabrication, and a variety of methods can be used to manufacture such components. Afte r briefly considering these points, this paper discusses some aspects encountered in the development of a facing brick panel built in a jig by traditional methods.

2 . ADVANTAGES DF PREFABRICATIDN

The major advantages of prefabrication over tradition­ally laid work cari be summarised as follows:

(a) Work is carried out in a factory, or at least un­der factory conditions , thus avoiding the effects of weather .

(b) The materials used and the ac tua l construction process can be subjected to more careful control, so that the resulting brickwork s hould be superior to much normal traditional work .

(c) With many systems, decora tive bonds, recesses and other features that would normally be too expen­sive or time consuming in traditional work , can be readily incorporated into panels.

(d) Prefabrication can accelerate the entire site construction, enabling earlier occupancy of the building with a resulta'nt financial contribution.

(e) Site problems involving congestion of materials are eliminated. No storage is necessary on site , since panels can be lifted from the lorry and placed directly in position.

Naturally fresh problems are also introduced, such as fixing , jointing and hand ling , but considerable ex­perience is available with other materiaIs , and many known techniques can be readily adapted for brickwork .

3. PREFABRICATIDN METHDDS

There are three basic methods of panel assembly: hori­zontal casting# vertical casting and jig laying . Nu­merous variations of technique exist within each of these categories . Discussion of several of these techniques is detailed in the papers listed in the bibliography (refs. 1- 9).

(a) Horizontal Casting

In this method the bricks are placed face downwards on to a compressible sealing layer, in a horizontal tray or mould. A thin grout is then poured or pumped over their backs, filling the joints betw·een them . The m~uld may be lightly vibrated to aid this process o

(b) Vertical Casting

Bricks arranged in a bond pattern are tightly clamped

1 . b . 1-1

between two vertical faces in a special machine. Grout is fed into the top of the machine unt il all the joint spaces are filled. Large pane ls that are true and plumb, with perfectly filled mortar joints, can be prod uced quickly.

(c) Jig-laying

Many early prefabrication systems were based on jig­laying. This involves traditional brick layi ng using jigs to improve productivity and facilitate quality control o The method requires relatively simple equip­ment and production facilities. Thus the 'fact ory' can be established either at the brickworks, the con­tractor's yard or on the s}te itself .

This latter approach, (c) , was adopted in the current work .

4. EXPERIMENTAL WDRK

4 . 1 Description

The purpose Df the work was to carry out a small scale exercise to simulate the on -site construction and erection of bri ck panels as used in a typical frame structure . The arrangement of panels is illustrated in Figure 1 . Basically, it consisted of an L-shaped re­inforced concrete strip foundation , with three hollow brick columns , built off the foundation, together with two steel channel posts . The cavities in the brick columns contained reinforcement, and were gr outed with concrete . A frame construction was thu~ simulated . Four brick pane ls, two storey-height and two sill height , were jig-built by traditional methods adjacent to the strip fouridation by a local contractor, and subsequently hoisted and placed into final position by crane . Lifting was by means of canvas slings from a steel spreader beam.

Particular attention was directed to the following points.

(1) Appearance

This is obvious ly of importance for facing panels , and care was required with both bonding and pointing . Bri cks used were sandfaced perforated wirecuts . Spe­cial bricks were used around the perimeter of each panel , as illustrated in Figure 2 . Use of such units resulted in a number of advantages, namely:

(a) the detailing of the joint is facilitated and, because it is expressed , the panel becomes aes­thetically distinctive as a special product.

(b) the risk of damage to the arrises is minimised during any transit and placing,

(c) panels can be used in both internal and externaI corners without breaking the dimensional grid . Figure 2 illustrates typical junct i ons between pane ls .

(2) Dimensional accuracy

Panels were bui l t i n speci al timber jigs . Accuracy was closely controlled. This is necessary where panels are to fit into a modular grid .

(3) St-rength

Adequate sfrength for the pane 1 is necessary to permit lifting and placing in position . In finished work the panel must be strong enough to resist wind, impact loads, and frame movement . Reinforcing w·as therefore placed at intervals in the horizontal joints, as shown in Figure 1. The morta r used WBS 1 :1 : 6 by volume .

1.b . 1- 2

(4) Fixing

Special fixings were designed to hold panels to the structure. Figure 3 details those initially used. These gave ris e to some problems during the first erection trial, as discussed in section 4. and t hey were subsequently modified as illustrated in Figure 4.

(5) Jointing

Joints must exclude the weather. be simp~e and econo­mic, with an aesthetic appearance, accommodate differ­ential movement, and allow for the manufacturing tol­erances within the framework Df dimensional co-ordin­ation. A 'dry-joint' system was provided for the vertical joints, using a proprietary filler strip.

The bed joint for each panel was made as follows:

(a) two rigid packing pieces for each panel were set and levelled on a 1:3 mortar bed at an appropri­ate distance apart.

(b) After this had hardened, and when panels were ready for erection, a 'ridged 50ft mortar bed was trowelled between these support pads and covered with a layer Df 'Hyload' D.P.C. along the whole pane 1 length.

(c) The panel was then positioned on to the bearing as quickly as possible, 50 that the mortar bed was squeezed out to provide a uniform bearing.

4.2 Dbservations

On the basis of the trial, a number Df observations can be made, some of which would lead to modifications in future work.

(1) Construction

An improved building jig is required, the design of which should not present difficulty. It is important that the bricklayers have no chance to build a diff­erent number Df courses than required, as this would affect the fixing positions, and must be avoided.

No problems were encountered when incorporating rein­forcemsnt and fixings.

(2) Lifting

Use of canvas slings was unsatisfactory. Chamfered bricks along ths bottom of the panel meant that it did not hang vertically, and 50 was difficult to handle and align. Further examination showed this problem could be overcome by careful positioning of the slings, but this remains an unnecessary complication.

Slings were difficult to remove when the panel was in position, and could be a cause Df damage to the D.P.C.

In the particular exercise described, slings were un­avoidable, but thsrs are several other ways in which panels could be lifted. For example, where the brick contains largs psrforations, a lifting hook and con­tinuous rod can bs grouted in. Alternatively two per­pend' joints could be omitted towards the ends of each panel, say three courses from the base, and a metal plate pushed through the perpends, to which suitable wire bonds could be attached.

(3) Mortar bed and D.P.C.

It is important that the panels squeeze out the mortar bed to give adequate, even bearing. To ensure this, the bsd should be laid immediately prior to position­ing the panel. When the small panels were removed after an initial trial, the bearing achieved was found to be satisfactory by this method.

The D.P.C. - must be lapped, and should not extend

beyond the front of the concrete slab unless a special flas h ing is incorporated.

(4) Fixings

The fixings initially used, and illustrated in Figure 3, were unsatisfactory. It is necessary for any fix­ings to cope with a degree Df tolerance, both in panel size and position, and a degree of inaccuracy in the setting out of the bolts. Horse-shoe-shaped packing pieces of several thicknes ses were required to cope with such problems. Location of brackets to make a temporary support while the crane was holding the pane 1 in position was not easy.

The amended fi xi ngs used in the final erection of alI the panels, illustrated in Figure 4, retained the stud fixing built in to the horizontal mortar joint Df the brickwork, but used vertical unistruts with a captive nut, built into the two brickwork columns . Vertical slots in the steel columns gave tolerance on fixing. The new angle cleats with horizontal slots gave alI the degrees of movement necessary, and eliminated the need for packing pieces, in addition to being easier to fix.

Theffifi xings illustrate one satisfac tory solution to the problem, but alternative systems could usefully be considered for the future.

(5) Panel Support and positioning

Although no major problems were encountered in sup­porting the panel on initial release of the crane, it is considered some temporary support such as push-pull props, should be a vailable.

Positioning on the concrete to achi e ve the required cavity width was found to be e~sier if temporary spac­ing pieces, ass ess e d by ca reful meas urement at the base of each panel, were positioned at the bac k of the D. P.C . against the concrete upstand. A similar verti­cal member between panels enabled the appropriate joint thickness to be achieved.

(6) Jointing

A number of jointing materiaIs were examined. Those requiring compression to be exerted during pane 1 pos­itioning to achieve a seal were unsatisfactory since insufficie nt horizontal movement of panels was poss­ible at this stage. For thi~ reason, use of a cellu­lar neoprene material sleeved with a waterproof self­adhesive composition proved unsatisfactory, as also was a wax-resin i mpregnated e xpanded polyurethane foam. A pre-compressed bitumen impregnated foamed polyurethane strip proved the most suitable of those examined.

Modification of the special edge bricks on the panels, to gi ve a wider bearing area in th e j oints, would be an advantage. In addition this would increase sta­bility of the panels during handling, without affect­ing the.aesthetic appearance of the joint.

Examination of other alternati ve materiaIs 1s however necessary to extend the range of suitable sealants .

5. FURTHER WORK

It has been established that panels of the type de­scribed can be made and erected sat isfactorily, to give an efficient and pleasing claddi ng. It is now necessary to plan the next stage of the development work. The observations made in 4.2 (4), (5) and (6) point to the need for further consideration of the jig design, method of fixing and jointing material. At the same time , a prototype s tructure should be designe d to test more conditions and to give a greater area of

panel for the research team to assess. It is essen­tial that such a prototype should be built as a nor ­mal job, and not as apure development project, i . e . a building contractor should perform his normal func­tion Df erecting the frame and should only r eceive the panels from the manufacturers . One function Df the prototype will be to establish a cost - time relation­ship for panel e r ection .

Concurrently with the bu ilding of the prototy pe a mar­ket research investigation is required, to establish the potential market and to dete rmine whether any al­terations to the design are necessa ry to suit the pur­chaser ' s needs . These can then be incorp orated into a final design based on both expe rience from the manu­facture and e rection Df the prototype, and the results Df the market research .

The building i ndust ry, at present, is not sufficiently buoyant to need a ma jor injection Df prefabricated brick panels. The tests described above , together with the p r ojected work, should enable a properly tested and tried method Df manufacture and erection Df prefabricated brick panels to be available for the future upturn in building effort.

6 . BIBLIOGRAPHY

1. Foster, O., "progress in Brickwork Pr efabricat ion -a Compa rative Study " . Th e Brick Bulletin , VoI. 6, No . 9, 1967 .

2 . Foster , O., Laird, R.T ., "Vertical Casting Df Brick Panels" Trans . Brit . Ce ram . Soe . 67 (6) 221-31 , 1968.

3. Zenobi, G. V., Szerdahelyi, O. , "14-Storey buildings in Switzerland with brick wall elements prefabri­cated by the Pr eton process : Designing Engineer­ing and Const ructing with Masonry Products , Ed . F. B. Johnson. Houston , Texas, Gulf Publishing , 1969 pp . 460-67.

4. Bryrup . J .• " P refab~icated Brick Facing Panels : An I nte rnational Survey". S . I . B.M.A.C. Proceedings . Ed . H. W. H. West, K. H. Speed , 1971 pp . 8- 14.

5 . Hamm , P . C., "The Oevelopment Df Prefabricated Brick Panels in So uth Africa ", ibid . , pp . 15-22 .

6 . Anon . , "Prefabricated Brickwo r k. An outl1ne Df International Oevelopments ", Brick Oevelopment Association , London. 1972.

7. Erdmann, M.P .• et.al . , "The Philadelphia National Bank - A case study in Prefab r icated High Strength Masonry ". Ziegel Oocumentation 3rd International Brick Mason ry Conference Essen 1973; Bonn, Bandes­verband der Oeutschen Ziegelindustrie. 1975 , pp . 13-17.

8. Wa l t , H . • "T he Preton System: Prefab r icated Con­struction with Masonry Brick ", ibid . . pp . 594-96 .

9. Finizi , S .• "Automatic Plant for Pre f abricating Brick Wall Units ", ibid ., pp . 597-99 .

ACKNOWLEOGEMENTS

The authors acknowledge with thanks the assistance given in this work by Mr. M. Simons , R. I .B . A. of Triad Architects and Planners , Mr.E . Papper, Red l and Te ch­nology Ltd . , and Mr . P . Vallis , Red l and Br icks Lt d.

~ . b . 1-3

1. b. 1-4

storey height panel

rem torcement bric kwork .

column

2600", brickwork remtorcement

1

Fig. l Arrangem ent af panels

column

,[2 vertical ed

l a) S . ge unlt pecl al uni t ~ (b) Junct · lons; t o panels;

Fig. 2

pa ne l

Ihreaded slud f ix in';j built into br ic kwor k

col umn

Fi g 3 Typica l f i x ing brac ke t Isubsequen tl y modi fied )

1 . b . 1 - 5

pane l column

channe l inser i

fig 4 Mod i f ied f ixi ng brack et