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WINSTANLEY COLLEGE

divetging anglesand roundedcomers illustratethe versatility andflexibility ofbrick diaphiagmwallconstruction.

By Bernard Taylor & StewartLord Technical Services DepartmentWigan Metropolitan Borough Coundl.

MUSIC SUITE

Diaphragm brickwalls have helpedprovide this attractivemusicsuiteat a sixthform cQllege near Wigan.The building's highsound insulation,

ENGINEERS FILE NOTE NO . 10 .

May 1991

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DEVElDPMENTASSOCIATION

INTRODUCTION

ARC HIT E C T' S B R I E F

Conversion of an existing edge-of-townsecondary school into a sixth formcollege resulted in the need to provide anumber of high quality specialistteaching facilities to meet the demandsof A-level courses. One of the first was a£150,000 music suite which was handedover to The Metropolitan Borough ofWigan in August 1982.

The new music suite was requ ired toprovide two teaching studios, fivepractice rooms, a recording studio, officeand stores. The component parts of thesuite needed to be acoustically insulatedfi m eaeh other and from adjacentG Ie flfiiltllngs. The Department of

lication and Science guidelines alsodictated the proportions of the rooms , inparticular the.avoldance of right anglesand parallel . '. ich,cjlLl§.e repeatedsoupdrefl . ~ ~-

~"i~- ~

Plan"'_ Form Cohge

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I

---'-.:-=-.:.-=--==-.:":::' :-=-':=-':~ j - - - - - - ­WlNSTANlIY ROAD

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ce

Recording Room

Music Studio 2

Music Studio 1

Practice Rooms

Ag. 1 layout Plan.

THE SOLUTION

The architect opted for a three blocklayout· one for each of the two teachingstudios and the th ird for the five practicerooms.

The central entrance foyer includes theofficewhile the stores, recording studioand three audio booths are incorporatedinto the larger teaching block.

The blocks were orignially conceivedin cavity wall construction using a 215mminternal blockwork and 103mm externalbrickwork. The need for a sloping roof ­for acoustic reasons - resulted in wallheights of up to four metres. This wouldhave required substantial piers to resistwind loading, which were considered tobe unsightly intrusions , and would alsohave disrupted the acoustic quality ofthe studios.

Diaphragm walling was thus examinedand found to offer a structurally efficientand cost effective way of realising thedesign.

The perimeter walls for each of thethree blocks are 440mm wide with singlebrick diaphragms tied in at approximatelyone metre centres. Each block is aseparate structural unit with a reinforcedconcrete ground beam supporting each .perimeter wall. A 150mm deep reinforcedconcrete capping beam is strapped tothe top of the wall and th is in turnsupports 550mm deep plyweb roofbeams at 1200mm centres. The cappingbeam rests on the inner skin anddiaphragms while the outer skincontinues upward to form the outer leafof the parapet wall.

The corners of each perimeter wall areset out on a 600mm inside radius andeach curved corner contains a total offour diaphragms. AverticallOmm widemovement joint is provided at one side ofeach curved corner.

Bricks are Armitage Minster Rusticwith a conventional 1:1 :6cement:lime:sand mortar. Stretcher bondis used for all brickwork apart from thecurved corners. Initially these wereintended to be special bricks laid instretcher bond. The need for twodifferent radius specials prompted a re­examination, however, and it wasdecided to use snapped headers sincethis was felt to provide the most costeffective method of constructing thecorners.

Expamef Ca ving

Jot>lite pOlystyrenesheet insulation

550mmdeepptyweb roo beam

~ 1m long wa ll stropfixed to'NQlI

and copping beam

Mild Steel Brod<elNailed to RoofBeam

and bOlted 10 Copping Beam

Uned Roofing Moteriol

Ag. 3 TypIcal wall SeclIon.

DPC_ _ .....

Insulation

Ag. 2 c:on- Detail

i7mm x 3mmGalvcnisednat fish-tailed

wall tiesevery course

t)mm Movement Joint

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CONSTRUCTION

Work started in May 1981 and wascompleted in August the following year.Although the contractor had notundertaken diaphragm walling before ,he was able to complete the project ontime and within budget. Much of thissuccess was attributed to the contractorproducing a setting out drawing forvirtually every course of brickwork. Afullsize trial corner was also built on site toverify the feasibility of using snappedheaders in place of curved special bricks.

COSTS

The cost of the building was £150,000 fora gross floor area of 310square metres,or £484 per square metre, which wasapproved by the Department ofEducation and Science.

CONCLUSION

This project demonstrates the use of astructural brickwork solution, based ondiaphragm walling, to be a cost effectiveand appropriate method for building.The lack of internal piers is bothaesthetically and acousticallyadvantageous in this particularapplication.

The project also demonstrates thattight radius curves can be built withoutthe need for special bricks.

ACKNOWLEDGEMENTS

Client: Wigan MetropolitanBorough Council

Designers: Department ofTechnicalServices,MetropolitanBorough ofWigan

Contractor: G& JSeddon UmitedFarnworth, Bolton

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•E D ITO R' S NOT E

The attention of the reader is drawn to thecontradiction between achieving thinnessin the overall depth of a diaphragm walland at the same time increasing itspropensity to rain penetration. This wasa consideration at the time the designerswere engaged in preparing their schemefor Winstanley CollegeMusic Suite. Inthis particular instance, a stretcher bondis used for the two wythes of brickworkwith the cross ribs or 'diaphragms' beingconnected to the outer and inner leaf byflat fish-tailed ties. These provide thestructural integrity of the Isection andare in effect the 'fillet welds' used toconnect two flanges and a web of awelded steel Isection. The provision andsize of the flat fish-tailed ties is the subjectof a separate calculation check for shearat the junction between the flange andweb.

In making their decision regarding theform of construction, the designers tookinto account the sheltered locality of thebuilding: no rain penetration problemshave occurred nor, it is believed, shouldoccur with this form of construction. Thereader should note, however, that if thisparticular type of section were used closeto a coast or in a more exposed location,there is a possibility of damp penetrationacross to the inner leaf unless some formof damp proof course is introduced at theilJnrtinn hptwppn thp outer f!;InOP ann

the web . This could be a sheet dpc whereholes are cut for the ties and are thensealed or, preferably bearing in mindworkmanship factors, a sprayed orbrushed applied dpc positioned on theinside of the outer flange for the width ofthe rib and an extra 100mm either side ofit. To achieve good application of the dpcthe base brickwork, which should havewell filled joints in compliance with goodworkmanship levels, should be left to gooff overnight. In this instance the outerleaf would be taken up slightly ahead ofthe cross ribs, the dpc applied accordingto the manufacturer's recommendations(and this would include around the baseof the protruding flat fish-tailed shearconnectors) and the cross rib and theinner leaf taken up together afterwards.

When the building is in a moreexposed location the designer may careto consider the use of, not galvanised flattie shear connectors but austeniticstainless steel. In coastal zones it isgenerally considered preferable to use316 (as opposed to 308) austeniticstainless steel due to the anticipated saltlevels. This guidance would apply toother areas, such as bridge abutments(or other highway applications) wheresevere wetting of the masonry by watercontaining salt ions can reasonably beexpected to occur.

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SCHEME CALCULATIONS

Using a deslgn wind speed at 3Om/s !he nell windpressure on !he windward wa ll is 0.55kN/m'•

039k~

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I---- O,16kN/m'

011 kN/m'L--.j

-0,27kN/m'

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A - am x 2 x (t115 + (0.44 -2 x am») - 0.278m'

I... - L(I... + I'r)

t115 x 0.44'- 12

(t115 -(2 x 0113») x (0.44- (2 x 0~3)')

- 12

- 6.93 x 'Kr'm'

_ !.to _ 6.93 x 10-' _ 315 'Kr'm'z X 0.5xO.44 . x

•Taascertain moments the wall is cons idered as acanftle'J9r propped at root tevet.

114,5m w V~I

Brtckdenslty - 2t1kN/m'Iloot load negUg!ble '''' stresscalculattons.

P_ - 2t1 x 4.5 x 0.278 - 26.4kN

3P"""" - 2t1 x 4.5 x 8 - 9.9kN

P MI -p: ±Z

26.4 t39 x (t115+ 0.910)'- - 0.278 ± 31.5 x 10-'

- 95.0 ± 89.4kN/m'

- + 0:18 or +0.006 N/mm'

(No bending tension develaped)

- 35.6 ± 501kN/m'

- +0.09 or -o.OI5N/mm'

Tensilestressis O.OI5N/mm' which is virtuallynegligible. (f"" - O.4N/mm').The oec:lIon IsOK lor lenIlon•

- wl' -0,55 X 4.5'M - - - - -t39kNm/m

- 8 8

9wl ' 9 x 0.55 X 4.5'M""" - 128 - 128 - O.78kNm/m

Try using 440mm diaphragm wall with 103mmbrickWO<k and diaphragms at 1013mm centres.Warst loading case is side wall with full heightwindows .

f"""" -9.990.278

0.78x (t115+ 0.910)± 31.5 x 'Kr '

440mm

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Neutral Axis

j _ Window Wintdow-Li......t tl I -~1 ,l ....... ,l l

9lOmm 1115mm 9lOm

Other calculaftons show that !he oec:lIon IsOK lorshear. A maximum campressIYe stress atO:l8N/ mm' Is deYeIaped • which is safety wilhln !hecapactly at brlckWO<k uslng 55N/mm' bricks In adeslgnatton (iii) (1:1:6) ma<lar.

';J;:;-~~~.-4j~~r>;~;e, views at the Association~~~;·~:'l~~;' n ken, scheme calculations have been included in the

i1eii lculations'and they should NOT be-read as such.

RIES BINDER

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