52.- Two Load-bearing Brickwork Buildings in Northern England by

A BSTRACT

The papa describes IWO calculated brickwork buildillgs; one a completed fOllrleell-slorey block of fiaIs aI Olc/ham, OI/c/ lhe 0111 ... a fOllr /fi!'e­slorey s/ellder cross-wall hoste! ar York. Foundatiol1s, wil1d loading anel

progressil'e collapse are {t;scLlssed in relatioll lo lhe desigl/ of bOlh blocks. COnlmenrs 011 file COIIS1rllCriol1 o/ rhe compleled block are inclue/eel and details o/ COS IS of struclUral lI'ork for both blocks are gil'en.

I. OLDHAM

R. E. BRADSHAW

Leeds Po/ytecllllic

and

D. FOSTER

SlrtlclIIral Cla)' Prodllcts Ltd, POlfers Bar, Herts.

Dellx Constrllctions en Maçonnerie en Briques Porteuses dans te Nord de I'AngleterJ"e

Le rappor' décrir deux cOl1slructions en mafollllerie eu briques calculée; rl/Ile est Ull b/oc d'apparlemenf, el1-t;erement achel'é, de quatorze é/ages à Oldham, /'Ollfre 1111 hôtel de quarre el cinq é/ages, al'ec des 11I/.1rs intéJ·· ieurs minces, d01l1 la COI1Sff/ICtiol1 esl projeclée à York. Les fOIlc/aliol/s, les charges dues ali l'et1l el /'a/faissement progressif som examinés en relalioll arec le /ype de cons/ruc/ioll des deux blocs. Les commen/aires SUl' la COH ·

Slr//clioll dl/ blac achevé et eles elétails sur le caiit de la conslruetial1 pour les deux blaes SOI1I don/lés.

This is a fourteen -storey block of ftat s forming part of a large housing redevelopment at Werneth , Oldham (Figures I and 2). The .rchitect suggested initially that load-bearillg brickwork would be suitable and economical and a preliminary structural illvestigation confirmed this. A number of plan a rrangements with varying accom· modation were swdied at the preliminary design stage. The final plan (Figure 3) is typical of tower construct ion and comprises two one·bedroo m and two two-bedroom fi ats per fioor , each with a livingjdilling a rea , kitchen and bathroom , with a centrallift, lobby and services area.

1.1 Slruclure

1.1.1 Foul1dations

From lhe initial site investigat ion it appeared lhat the block would be siled on boulder clay having a minimum thickness of 10 ft overlying sloping rock stra ta. A specia l­ist report on old mine work ings (prior to 1850 A.D.)

concluded that these presented no hazard and a reinforced concrete raft foundation was proposed. Excavation revealed that the rock outcropped above foundation levei at lhe sOllt h end ofthe si le so lhat a raft fOllndalion would bear partly (10 %) on rock and some differential founda­tion settlement would resulto

Zwei Gebiillde mit lasttl'agendem Zie­gelmallcnve,.k in NOJ'dengland

Der Au/satz beschreibt zu'ei reclmer­iseh kOllstruierre Gebaude aus Ziegel­mauenl'erk: eines ist ein bereils ferliggesle/lter I'ierzehn Srockwerke IIohe,. Wollllblock in 01""0111 !II1c/ c/as andere einjür rier bisjünj Slockll'erke l'Orgesehenes Hostel il1 York mil seh/anken Trel1nmauern. Fundamenl­ienmg, Windlasl lInd jorlschriftliehe Projilierul1g ( des Grundrisses) sind im ZusamlJ1e"hang mil dem En/ll"lllf beieler Gebiiuele erorlert. Amllerkwl· gen zur Ersle/lwlg eles jertigell Bloeks und Einzelhei/en der Kal1struklions­koslell fiir beide Gebiiude-Blocks \Verden gegebell.

The final scheme used 8 x 8-in. steel universal columns driven into lhe rock on a 6-ft square grid. Steel piles were chosen in preference to concrete piles to minimize lhe shortening under load. The maximu11l length of pile was 31 fi 6 in. and lhe minimum 9 fi 6 in . The minimum penetralion into rock was 7 ft. FIGURE I - Qldham : general view of completed building.

3t5

316 Two Load-bearing 8rickwork Buildings in Northern England

FIGURE 2- 01dham: entrance area.

1.1.2 Walls

Ali internai load-bearing walls are 9-in. (nominal) clay brickwork and externai walls 10-l-- in. cavity with both leaves load-bearing. Certain externai walls local to the stair tower retain approximately lO ft of earth fill, and these were designed to be reinforced vertically in lhe cavity with i -in.-dia. mild steel at 12-in. c/c. The cavity was filled with a I: 2: 2 cement: sand: pea gravei grout poured and compacted at four-course intervals.

1.1.3 Floor Slabs

An in sUu fia0 r slab was considered essential 10 provide a stíff horizontal plate at each fioor levei and lo restrain lhe walls. Consideration was given to two-way-span fiaor slabs but because of the difficulty of providing supporting

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walls on ali four sides and the fact that the externai cavity walls would require an il1creased thickness, it was decided to use a one-way span throughout. A 6-!--in.­thick 51ab was adopted to course with two 2i-in. brick courses.

1. IA Bas;s ol Des;gn

Live and dead loads were taken from CP 3, Chapter V, Loading,l and lhe stresses calculated in accordance with CP III : 19642

Floor spans are generally 12 ft and 9 ft between internai 9-in. walls 50 that the externai cavity wall parallel to the span is (theoretically) supporting its self weight only (Figure 3). In fact it will attract so me small portion ofthe flaor loading.

The 12-ft-span fioor af the living room is supported at one end 011 the externai 10t-in. cavity wall which is pierced by a 6-ft-wide window opening at each fioor leveI. A brickwork pier is provided on either side ofthe window opcning to support the additional load . Thi s wall was assumed to be axially loaded, the load being shared equally between both 4t-in. (actual) leaves. A very stilf reinforced-concrete ring beam was cast at the cavity wall /fioor slab junction (Figure 3).

Ali internai load-bearing walls were also assumed to be axially loaded for the following reasons:

(a) Cellular nature of plan and small room sizes re­sulting in lhe 6t-in.-thick fioor slab acting as a relatively st ilf diaphragm.

(b) Floor spans fairly equal, 12 ft and 9 ft generally.

(c) Live load small (31'Slbf/ft') compared with dead load 110 (Ibf/ft'), hence eccentricity of loading due to alternative fioor-Ioading bay is very smal l.

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BRICKWORK TYPE THUS : CD SEE TABLE 1

FIGURE 3- 01dham; typical Roor plan and sections through ring beam.

R. E. Bradshaw and D. Foster 317

comp le x X 24·2 5

12 -51 Cj 9'1I7S1 -!

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comp le;o: Y 2 4 ·25

11 ·7SIC 9- 12 - Si

IfQu ivolon t sys toz m o f shQor w ofl s

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(Stresses are in lbf/ in! for a verticalload of 1 lbfjin2 , i.e. for a build­ing wid th or 58 fi and wind load of 36'6 1bf/ ft 2 11lu1tiply by

[58 x (J6·6/ 12)1 ~ 177 Ibf/in '. ) FIGU RE 4-0Idham : wind loading N-S, prel iminary computer

designo

1.1.5 Willd Loadillg

The building was designed for a wind pressure of 24 Ibf/fl 2 assumed to act over the whole ofthe face being con­sidered. After completion of the building the draft CP 3 Chapter V on willd loading 2 alld B. R.S. Digests 99, 10 1, 105 3- 5 we re issued and caJculations were prepared for a revised ulliform wind pressure of 36·6 Ibf/ft 2 . The bellding stresses in lhe brickwork due to wind \Vere dete rmined in lhe usual way. 011 lhe assumption lhat each \Va li complex acts as a vert ical canti lever and lhat lhe over­turning mament due to wind is distribuled between the wall complexes in proportion to their st iffnesses.

wcll compl Ci!x X I s imil ar to Y -,

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At the time the preliminary schemes were being asses­sed (1965) an analogue computer technique for investigat· ing the behaviour under lateral load of interconnected shear-walls was being developed. 6 One preliminary scheme similar in plan form to the fina l scheme was analysed by Dr Soane, assuming that ali the wind load in the N-S direction was carried by the two central wall complexes X and Y acting compositely with a 14-ft width of fioor slab. The results showed that considerable inter­act ion was taking place, with a reduction of bending stresses of approximately 18 % when compared with those obtained by the vertical canti lever theory (Figure 4).

The criticai wind load ing is in the N-S d irect ion and for a wind pressure of 24 Ibf/ ft 2 il is possible to support thi s load on the two cent ral wall complexes X and Y a lone assuming vertical cant ilever theory (Figu re 5). However, for the revised wind pressure of 36·6 Ibf/ft 2 in both the N-S and E-W directions (see Figure 6) certain of lhe externaI IOf -in . cavily walls are now also considered to support a portion of the wind load. Most oftheexternal walls are pierced by window openings bllt only those where the width or height of solid brickwork around the opening is equa l to, or greater than, lhe window d imension, that is having the 'hole in wall ' type window, were considered for lhis purpose. T he stiffness of such walls was assumed lo be 50 % of the equivalent solid wall. ' ·6

1.1.6 Progressil'e Co//apse

Although the building was designed in 1966 before pro­gressive collapse was a feature of design, the require­ments of RP/68/03 7 are met as follows:

I. Plan form comprises a number of very stiff cellular lInits. Most walls have returns providing edge stiffening and a lternative load paths.

2. Floor slabs are in si/li reinforced concrete and bear completely over a li walls for their full thickness and a substantial ring beam is used. Hence in the unlikely event

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FIGURE 5- 0Idham: wind loading N - $ direction.

318 Two Load-bearing Brickwork Buildings in N orthern England

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t ~ INERTIA OF THESE WALLS 1"AKEN AS

H OU T OPENINGS 50 ·f. OF WALL W IT

F,GUltE 6--01dham: wind loading E- W direction.

of a lenglh of wall being removed , conside rable dee p beam ac tion could be expected fra m lhe walls and slabs Qver. Floar spans are one way but lhe geometry is such lhal lwo way aClion wi ll undoubled ly lake place.

3. Floors a re generally supporled on inle rnal walls' and dead-weight slresses will increase the resistance af walls to lateral pressures, where such press llres wo uld be 11105t criticai, i.e. in lhe lower sto reys.

4. There is no gas, hcnce there is a J11l1ch reduced risk of collapse caused by explosion.

5. Oamage lO lhe slruclure by fire is mosl unlikel y.

1.2 Materiais

The specificati on for ali mate riais was very si milar 10 lhe

Model Specification,8 except lhat the morta r strength requirements \Vere a little higher. Two morta r mixes only were specified for lhe complele scheme and lhe change from one mix to lhe olher was made only at one ftoor levei for ali wall s to avoid any confusion 0 11 site.

1.2. \ Bricks

Perforated and so lid wire-cuts and single- and double­frogged pressed bricks were used ro r lhe various strcngth calegories. The locati o n of lhe brick strenglh require­ments are given in Figure 3 and Table 1. Ali externai brickwork was laid in o ne strength brick s (approximately 8000 Ibfj in ') a nd in I :±:3 mortar. Samples of cer tain brick supplies were tested at different centres and it was eviden t that some testing machines were indicating lower brick crushing strengths than others.

1.2.2 Morlar

The spec ified mllllmum site cube strengths \Vere 1800 Ibfjin' and 450 Ibfjin' a t 28 days fo r lhe I :±:3 and I : 1:6 cement : lime: sand mixes respectively.

These strengths \Vere generally achieved and the one or two instances of low cube st rengths \Ve re due to in-

T ABLE I ~ I I\,'TE RNAL BRIC KWORK-STRENGTHS OF BRICKS USED (Ibf/ in»

i Posirioll marked 011 Figure 3 Storey M ortar

I 2 3

Tank room 3000 3000 3000 12, 11 , 10, 9 3000 3 000 3 000

8 5000 3000 3000 1 "". ) 5 000 3 000 5 000 Cement: lime: sand 6 ) 000 5000 5000 5 ) 500 5000 5 000

,

4 ) 500 5000 5000 3,2 7,500 5000 ) 000 } 1: ,:3 I 10 000 ) 000 ) 500 Cement: lime: sand

G, B 10 000 7000 10000 F 10000 10000 10000

consistent batching of materiai s by the mixer opera tor failing lO use the gauge boxes provided. In one ar two cases, when the 7-day morta r cube strengths were low, the penetration into the mortar joint of a cartridge fired pin was measured and related to a calibration curve. 9

The contracto r was anxious to use a masonry cement in lieu of lhe I : I : 6 mix but lhis was nOl allowed unlil a fter the tenth ftoor when a 1:4 maso nry cement :sand mlx was used to give comparable slrength.

1.2.3 Brickwork

Three brickwork cubes, 9 x 9 x 9 in. nominal , were pre­pared alongside cach slorey lift for eaeh briek slrength lIsed and lesled a t eilher 7 or 28 days. The crllshing st renglhs var ied considerably bllt the exerci se of pre­paring brickwork cubes for test ing made cIear to the site operatives lhat good qual ily workmanship was essential and thar lheir work and workmanship was being tested regularly.

Certain bricks a lready on site and in lhe wall gave

R. E. Bradshaw and D. Foster 319 apparently low strengths (see Seetion 1.2.1). Becallse it was difficult to obtain replacementsquickly it wasdecided to allow lhe work to continue, reinforcing lhe Duter leaf every alternate course with Bricktor as a precaution, and to test a cavity walI made of these bricks. The brick and mortar strengths lIsed in the test were:

Bricks: Ollter leaf 7550 Ibf/in2

Inner leaf 11 800 Ibf/ in' (slightly higher than the site) Morlar 3080 Ibf/in 2

The test walI , 4 ft 6 in. long withollt retmns and 8 ft 6 in. high , was loaded axialIy and failed explosively under a load of 695 tons. A single·leaf 4-1--in. (actual) wall in 1i 800-lbf/in2 bricks was tested at the same time and failed ai abollt 350 tons. The design load on a 4 ft 6 in. length af cavity wall Oll the 110rth and south elevations is 57 tons, and the load factor is therefore 695/57 = 12,3, whieh is welI able to take aceount of any slight deficiency af brick strength, any differential stresses due to tem~ peralure dilferences between the inoer and cuter leaves and any eccentricity af load which might existo

J.3 Comments 00 Constructioll

1.3.1 Merhod of Working One of the problems frequently encountered in load­bearing brickwork construction is that af ensuring C011-

tinuity of work for the bricklayer. If the projeet is sub­stantial and broadly symmetrical, this can be achieved by arranging the sequence of trades so that the walls are being raised in one half while floor construction is being done on the other. In this way bricklayers are followed logically by carpenters, steel fixers and then concreters. The target was initially one complete storey every 3 weeks, but this did not prove possible and the cycle beca me 4 weeks, with the exception of one longer period of delay due to bad weather in the winter of 1967- 8, when for a period of about 3 months work was suspended. This occurred despite lhe observance of lhe usual winter working rules pertaining in the UK 10 and serves to in­dicate that these are insufficient in extreme conditions. The only solulion then is temporarily to c1ad completely and heat the storey on which work is proceeding. This was not dane.

[n this and a number of other respeets the progress of the work was disappoinling. The contraclor had been nominated primarily 011 lhe grounds that he was a good 'trad itional' builder maintaining his own permanent staff of bricklayers. In facI the bricklaying team changed completely noL less than fom times before the job was complete! It is believed thal this was due primarily to lhe contractor's management troubles, although there is little doubt that disputes over rates of pay were also part of lhe cause.

In the UK, bricklayers usually work in self-employed gangs who bid for a job on a basis of a rate per thousand bricks laid or on rates per square yard for different types ofwall. Under such conditions productivity always takes precedence over good standards of workmanship, and in load-bearing work , where a high standard is demanded, the bricklayers have to be compensated by a higher rate so that their net earnings do not suffer. There is little doubt Ihal this combination of problems- bad weather, lack of eontinuity and the demand for a higher standard of work- eon!ribuled to the delays 00 the seheme.

1.3.2 Srandard of Workmal1ship

On the whole the work was acceptable, though some areus of walls had lo be pulled down and rebuilt. The quality of workmanship noticeably deteriorated as the weather worsened.

Perhaps lhe most common failing was lhat of in­completely filling the vertical joints and constaot super­vision is needed if it is to be achieved. This is expensive, particularly if a resident engineer is appointed, and here lhe clients would only allow, or cOllld only afford, a clerk of works who had much more than this one building to control.

In the corner of the building area the formwork for a fioor slab was wedged agains! the top two courses of the inner lea f and displaced them over a complete lengtb of wall so that lhe fioor was elfectively earried solely on the outer leaf in lha! area. By the time the damage beca me apparent another storey had been raised over the area, so remedial measures were complicated and expensive. A new 4-!--ill. skin of briekwork was built against lhe existing inner Ieaf from lhe foundation up to the point where the damage had occurred. This new skin was attached to the exisling one by expanding bolts and reinforcement and pinned hard against the slab soffit by si ates rammed home in cement-sand mortar. Before removing the damaged briekwork and before building lhe new skin, the cavity was pumped full of foamed urea­formaldehyde. This prevented broken brick and mortar from falling into the cavity.

1. 3.3 Brickwork and Damp-proof-courses~Flash;ngs

Over the ring beam a continuous layer of pitch-polymer damp-proofing material was placed, arranged so lhat it would discharge to the exterior any rain water which penetrated the outer leaf- a typical slandard detail in lhe UK (Figure 3). Particular care was taken to ensure that this projeeted -l- in. from the face of the building, one object being to avoid staining of brickwork or concrete by rainwater running off one to the other. Bricklayers hate doing this- they have always been used to setting the fiashing slightly back from the face and neatly finishillg the joint over it. While this may be acceptable in eon­ventional two-storey housing, it eertainly should not be tolerated in load-bearing struetures becallse it leaJs to spalling of mortar as the fiashing slowly compresses.

1.3.4 Prel1ention of Condensatiol1

The junction between externai wall and floor slab, where lhe latter is taken through the wall to the outside face, is a potentially serious cause of heat loss , because the thermal conductivity of the reinforced concrete slab is high. Despite partial central heating, the intermittent use of the flats often results in eondensation at the posi­tion mentioned. One effective way to reduce its incidence is to provide a 2-ft-wide strip of -l-in. foamed polystyrene board around the perimeter of the building. This was done by laying the insulalion on the formwork before pouring the slab.

1.3.5 Non-Ioadbearing Walls

Where it was deemed necessary to avoid load being carried by thinner walls, a compressible layer of foamed polystyrene was placed along the top before the formwork was laid.

320 Two Load-bearing Brickwork Buildings in Northern England 1.3.6 Prol'ision of Holes for Senices

Oreat care was taken during the preparatioo of the draw­ings to indicate holes and allow for ali services. No chasing was allowed at any time and ali electrical 'drops' to switches were in thin 'top-hat' sections concealed in the plaster.

1.3.7 PrOl>ision for Drying Oul

The British weather manages to soak nearly ali buildings during construction. This job was no exception. Modern methods of drying out, such as powerful dehumidifiers, are necessary if finishing work is to proceed aI a reason­able speed. Considerable troubles were experienced in Oldham beca use of the wet weather, which appeared to persist for most of the contract period . A further cause of water dripping down the building was the provision of holes in the slabs for checking the vertical accuracy of the structure and to help in the setting out afresh the internai walling on each fioor.

1.4 Costs

A comparison of the cost of this brick building with a taller reinforced concrete framed structure which was being built at the same time is set out below. The saving by using load-bearing bdck in lhe superstructure only is :

n·41 - f3-14-l:

fQ'26-l: per square fo oL

This is about 7·7 % and is within lhe range of 5 to 9 % saving on total cost, which has been generally experienced. However, lhe following details show that some of this saving was offset by foundation costs.

Block 11

(Floor area approximately 58 250 ftZ)

Concrete frame and fioors: piled foundation s. Substructure total cost approximately :

EIS 500, i.e. EO·26 ft'

Superstructure total cost approximately:

EI99 000, i.e. 0·41 ft'

Total cost approximately:

f214500, i.e. E3-66-t ftz (Contains seventy dwelling units).

Block 18

(Floor area approximately 40 700 ft') Concrete fioors ; brick walls load-bearing ; piled founda­tions. Substructure total cost approximately:

EIS 000, i.e. fO· 36-l: ft'

Superstructure total cost approxirnately:

EI28 000, i.e. EJ'14tftZ

Total cost approximately:

EI43 000, i.e. n'51 ft'

(Contains forty-nine dwelling uoits).

It will be seen that subslructure costs per square foot were much higher on lhe fifteen-storey load-bearing scheme than on the eighteen-storey framed reinforced concrete structure despi te the extra height of the la!ter. This is thought to be due to differences in the type of piling. In addition the brickwork job had a 2-ft-thick raft, whereas the other was on individual pile caps.

2_ YORK

This is a four/five storey YWCA residential club. Construction commenced in 1970. The site is in a residential suburb, the building height was to be kept as low as possible, and the major desigl). requirement was for a repeti tive unit. The four-sided court-yard plan,

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FIGURE 7- York: parI typical floor plan (S wing).

R. E. Bradshaw and D. Foster 321

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~-_._. _ STEEL BEAMS AT

1st FLOOR LEVEL

(N &. E WINGS ONLY)

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FIGURE 8-York: pari grOlUld-floor plan (E wing).

four storeys in heighl on eilher side of lhe five-slorey central services and kitchen area, developed naturally (Figures 7 and 8). Each unil is divided into small privale living cells and il was a nalural developmenl Ihal lhe walls between cells, providing separation and sound insulalion, should also be load-bearing.

A preliminary structural investigation confirmed that mosl of lhe load-bearing walls could be calculaled brick­work of 4t- in. aclual Ihickness. Certain non-slandard and open areas were required at ground-floor levei and serious Ihoughl was given lo lhe possibility of providing a framed slruclure up to firsl-fioor leveI. In lhe event lhe subsoil conditions were such lhat strip footings with line loading were considered to be more economical lhan lhe SpOI bases Ihal would be required for columns. The final scheme is load-bearing brickwork Ihroughout.

2.1 Structure

2.1.1 FOllndo/iolls

Asile invesligalion revealed clayey sand and silly clay to deplhs of aboul 6 fi below lhe surface overlying firm and soft lo firm clays.

On the basis af triaxial compression and other tests nel bearing pressures of 0·75 lonf/ft 2 and I·Olonf/ fI 2

were considered applicable to lhe design of long slrips and isolated square bases respeclively founded 3 fi below the surface. The sett lemenl under load due lo consolida­lion of lhe clays is likely lo be about I in. and il was felt lhat a reinforced-concrete strip footing foundation acting compositely wilh brickwork foundation walls would cope more satisfacto rily than SpOI bases in bridging any local soft pockets and, owing to ils stilf box-like action, minimize differential settlement,

2.1.2 Wolls

The main cross-walls belween bed/sitting rooms are 4i -in, actual thickness as also are most corridor walls, ExternaI walls are generally li-in . cavily conslruction

but are increased to 15 in. either si de of lhe centre block; certain walls to open arcas between foundati ons and first­floor levei are also 15-in. thick. Between foundation and firsl-fioor, paris of bOlh the N and E wings are non­repelilive and lhe load-beari ng walls of 4t -in. aClual thickness above betweell first-fioor and roof are supported on universal beams spanning 15 ft c1ear onto the 9-in. inner leaf of lhe 15-in. walls (Figure 8). The sleel beams are encased in lightweight concrete to reduce dead weight.

2.1.3 Floor Slabs

Some form of ;n S;lu reinforced-concrete fioor slab was considered essential to provi de horizontal plate action at each fioor levei and to tie adequalely the lops of ali walls at each fioor.

The dead weight of the fioor was kept low becallse of the poor sub-soil and a composite fioor of wood-wool and ;11 S;IU concrete ribs and topping was chosen. A reinforced-concrete ring beam within the fioor depth is cast over each load-bearing wall to provide a tie at each fioor levei and to assist composite action in the unlikely event of a wall being damaged.

The ftoors generally span 9 ft clear betwecn internai 4t -in. walls, Ihal is parallel to lhe exlernal walls, but the slab is carried over the inner leaf of the cavily walls at each floor to provide additional stiffness to the structure as a whole. At second-fioor levei lhe slab is carried Ihrough the ouler leaf also to reduce any dilferential movement between the inner and outer leaves.

2.1.4 Basis of DesiglJ

Live and dead loads were taken from CP 3, Chapter V, Loading,1 and the stresses calculated in accordance with CP 111: 1964.2 Allload-bearing walls were assumed to be axially loaded.

Special emphasis was placed on lhe stilfness of lhe cellular units and the door openings to the bed/sitting rooms are mid-way between cross-walls in order to

322 Two Load-bearing Brickwork Buildings in Northern England provide stifferung retum walls (Figure 7).

Window openings are generally of the 'hole in wall' type, again to improve the overall stiffness af lhe structure. By this means it was possible to use the 4t-in.-thick cross-walls for the main load-bearing structure for lhe major par! of lhe scheme, Ihereby effecting a considerable saving in cosI, when compared wilh other hoslel blocks having thicker walls or different struclural support.

The N and E wings of the building have a non­standard layout of accommodation including a club room, 15 x 33 ft, and lhe director's Hat. Through careful plan­ning by the architecI, load-bearing walls from above conlinue through to foundation in ali but two areas where steel beams are provided, aI firsl-floor leveI (Figure 8).

A movement joint is provided on either side cf the centre block.

2.1.5 Wi/1d Loading

The stresses due to wind loading are quite small and well wilhin lhe 25 % increase in compressive stress alIowed by CP 111. '

2.1.6 ProgressÍ\'e Collapse

The requirements of RP/68/03 7 were considered although the building is only four/five storeys in height.

The adoption of the slender cross-wall necessilated a very stiff plan form and this logether with the i/1 Si/li

concrete ring beam within lhe floar depth and cast Qver each load-bearing wall , will assist composite action in the unlikely evenl of a length of wall being removed.

There is no gas in lhe building, and the delailed com­ments given in Section 1.1.6, excluding lhe reference to the substantial ring beam aI each fioor levei over the externai walls, are also relevant to lhe bui lding at York.

2_2 Malerials

The specificalion for ali materiais is similar to lhe Model Specification.8

Ali brickwork up to first-floor levei is in bricks of 4000-lbf/in' strength and above this leveI in 3000-lbf/in' bricks. A 1:1:6 cement:lime:sand l110rtar is lIsed Ihroughout.

2.3 Costs

The accepted lender price was f204000 and the following figures relate to the st ructure.

Subslrucrure: Total cost approximalely:

fl3 220, i.e. fO'36 ft'

Superstruclure:

Brickwork lotai COSI approximately :

i24 650, i.e. fO·66t ft'

Floors, roof, steelwork; total cost approximately:

f23 890, i.e. fQ'64t fI'

Total structural cost approximately:

f61 760. i.e. fl·67ft'

ACKNOWLEDGEMENTS

O/ditam Selteme: the archilects were the Werneth Design Group; quantity surveyors: Cameron Middlelon & Lees; concrete design by Truscrete Ltd; brickwork design by R. E. Bradshaw; general contraClOr: Thos. Partinglon.

York Selteme: the archilecl was P. M. W. Knowles ; quanlity surveyors: Turner & Holman ; consulting engineer: R. E. Bradshaw.

REFERENCES I. BRITISH STANDARDS I NSTlTUTION, Code of Functional Require­

ments of Buildings. Chapter V, Loading, CP 3: 1952; and drafl revi sion 1968.

2. BRITISH STANDARDS I NSTlTUTION, Structural Rccommendation s for Loadbearing Walls. CP 111 : 1964.

3. BUILDlNG REsEARCH STATION, Digest 99, Nov., 1968. 4. BU1LDING RESEARCH STATION, Digest 101, Jan., 1969. 5. BUlLDING RESEARCH STATION, Digest 105, May, 1969. 6. SoANE, A. S. M., lnteraction of Brickwork Walls and Concrele

Floors under Lateral Load. 'Oesigning, Engineering and Constructing with Masonry Products'. Ediled by F. B. Johnson. Houston, Texas, GulfPublishing, 1969. pp.278- 284.

7. l NSTlTUTION OF STRUCTURAL ENGINEERS, Guidancc on lhe Design of Domestic Accommodation in Load·bearing Brickwork and Blockwork 10 A void Collapsc Following an Internai Explosion. LS.E. RP/68/03, 1969.

8. BRITISH CERAMIC RESEARCH AssoCIATION, Model Specification for Load·bearing Clay Brickwork . B. Ceram. R.A. Spec. Pub/. 56, t 967.

9, BUILDING RESEARCH STATlON, Tesling the Slrenglh of Mortars in Brickwork by Means of Cartridge Fired Pins. B.R.S. IIIfemal Note 70/65.

10. MINISTRY OF PUBLlC BUILDING & WORKS, Winler Building. London, !f.M.S.O., 1963.

11. BRADSHAW, R. E. and FOSTER, D., Assessment of Briti sh Dcsign Methods of Ca\culated Brickwork. 'Designing, Engincering and Constructing with Masonry Systems'. Edited by F. B. Johnson. HouslOn. Texas. Gulf Publishing, 1969. pp. 318-328.