C O M P O S I T E S T E E L B E A M D E S I G NS P E E D A N D S T R E N G T H

I N T R O D U C T I O N

Bison is the largest producer of precast concrete

floors in the United Kingdom.

The company has been a leader in the design and

manufacture of structural products since 1919.

There are five Bison factories throughout the

United Kingdom strategically situated to provide

a comprehensive service to our customers.

This brochure describes the economic and technical

advantages of composite steel beam design using

Bison hollow core and solid prestressed slabs.

Other products pioneered by Bison and for which

they hold a market leading position include house

floors for use both at ground floor and intermediate

levels and precast prestressed staircases produced

by a patented method which provides a product of

excellent quality at moderate cost.

In the field of structures too, Bison is a market

leader producing precast concrete, steel and

composite structures for use in retail, industrial,

commercial buildings and car parks as well as in

housing, educational and government projects.

Brochures on other Bison products and services for

the construction industry are listed on the back

cover of this brochure.

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Steel EconomyThe use of hollow core and solid slabs for compositesteel beam design provides a reduction in the totaltonnage of structural sections compared with theuse of non composite and composite metal decksteel solutions.

Speed of ErectionTime consuming activities such as propping, shuttering and concrete pouring are virtually eliminated.

Using a precast floor, a large volume of work is carriedout off site and saves what can be a complex andtime consuming site operation subject to the vagariesof the climate.

Reduced Site OperationsThe use of hollow core and solid slabs in compositesteel beam design greatly reduces the amount ofinsitu concrete work on site.

The ability of hollow core slabs to provide bay centres of 7.50m and greater, far exceeds that provided by a metal deck solution. This enables a reduction in the number of steel members for abuilding and consequently in site programme time.

The provision of factory welded shear studsremoves this operation from the site critical path.

Optimisation of Shear Stud DesignThe use of hollow core and solid slabs for compositesteel beam design allows the optimisation of shearstud design due to the lack of restriction in positioningthe shear studs.

Elimination of DeflectionThe use of hollow core and solid slabs in compositesteel beam design eliminates the difficulties experi-enced with local deflection of a metal deck solutionbetween steel beam supports.

Fire ResistanceStandard precast floors can be supplied with a fireresistance of up to 2 hours.

T H E A D VA N T A G E S

Immediate Unpropped Working PlatformOnce a precast floor is erected, it is immediatelyavailable as a working platform. Steel deck systemsby comparison can present problems in achievinglevel surfaces whilst concrete is poured and in providing access whilst in the propped condition.

No ProppingPropping is not required with hollow core slabsdesigned compositely into a steel framed building.Compare this with the large amount of proppingrequired with fully insitu and semi-insitu floor systems.

Diaphragm ActionPrecast floor slabs are structurally grouted to providea floor with full diaphragm action as required inmost multi–storey frames. This can be achievedwithout a structural topping.

Finished SoffitsPrecast floors are manufactured on high qualitysteel beds and are suitable in appropriate cases for direct decoration.

Factory Engineered ComponentsPrecast floors are factory produced,being manufactured in an environment which is morereadily controlled than a building site. Qualitycontrol systems are properly implemented and are independently examined on a regular basisunder the British Standards Institution QualityAssurance Scheme.

Product ApplicationComposite steel beam design offers an economicsolution whenever a steel frame is being considered.It has been proved successful in the design andconstruction of office, commercial, industrial, hotel,stadia and car park developments.

Raised Access FloorNo additional finishes are required to the top surfaceof the hollow core units prior to the installation of araised access floor.

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C O M P O S I T E S T E E L B E A M D E S I G N

DefinitionComposite Steel Beam Design is the use of hollow core and solid slabs togetherwith insitu infill in conjunction with welded studs onto steel beams to enablethe slabs and steel beams to act compositely together enhancing the load capacityof the steel beams.

Research and DevelopmentThe research and development of the application of precast hollow core andsolid slabs to the design of composite steel beams is the result of severalresearch projects undertaken since 1993. These have been supported by theEngineering and Physical Sciences Research Council, the Precast FlooringFederation and Bison Concrete Products Limited.

The research has followed a combination of experimental testing and finite element modelling. The testing consisted of a parametric study demonstrating the viability of this method of design and a further series of tests to provide thestatistical basis. This provides the data for the Design Guide undertaken by the Steel Construction Institute and the Precast Flooring Federation, supportedby a Department of the Environment, Transport and the Regions research grant.

Bison acknowledge the research and development carried out by:• D. Lam - BEng, MPhil, PhD, CEng, MIStructE, MIMgt, Leeds University.• K.S. Elliott - BTech, PhD, CEng, MICE, MIMgt, Nottingham University.• D. A. Nethercot - BSc, PhD, DSc, FREng, FIStruct E, FICE, Imperial College.

Design SupportBison Concrete Products Limited are committed to providing the technical support together with computer software enabling engineers to maximise theirdesign options for this product.

The Components

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D E S I G N C O N S I D E R A T I O N S

The design procedures, to B.S. 5950 Part 3, described within the research and development projects havebeen adopted in the available software and are summarised below:

Shear Stud CapacityThe design shear resistance of the studs is the lesser of the following formulae:

Effective Width of Compression Area

fcu = insitu concrete strengthø = diameter of reinforcement fy = characteristic strength of the reinforcement g = gap between ends of precast units

With a maximum beff of the actual width.

? = 0.2 ( h/d+1) h = height of the stud.d = is the diameter of the shank of the stud.fu = is the specified ultimate tensile strength of the material of the stud but

not greater than 500 N/mm2.? = a factor which takes into account the gap width g (mm) and is given as

0.5 (g/70+1) ≤ 1.0 and g ≥ 30mm.? = a factor which takes into account the diameter ø of transverse high

tensile tie steel (grade 460) and is given by 0.5 (ø / 20+1) ≤ 1.0and ø ≥ 8mm.

? = transverse joint factor = 0.5 (w / 600+1), w = width of hollow core unit.fcp = average concrete cylinder strength = 0.8 x average cube strength of the

insitu and precast concrete.Ecp = average value of elastic modulus of the insitu and precast concrete.?v = partial safety factor for shear stud.

beff

Dslab

DP. N.A P. N.A

Py

Py

Rc = 0.45 x fcu; x beff x D slab

Summary of Design Considerations• Generally a maximum of 250mm deep units, including any topping.

• Shear studs are generally 125mm x 19mm diameter. The use of other studs should be referred to Bison Concrete Products Ltd.

• The maximum of (1.0m + the gap between the units) approximately 1.05m of compression width for internal beams.

• The maximum of (0.5m + the distance from the edge of the unit to the end of the concrete) approximately 0.63m of compression width for external beams.

• The optimum beam flange width is 178mm for construction purposes. The use of smaller flanges must be referred to Bison Concrete Products Ltd.

• The reinforcement required for transverse beam / unit interaction is recommended as T16ø at 300mm centres to enable sufficient slip for partial interaction.

• The shear stud strength is related to the interaction of the concrete strength and properties, the geometry of the unit and transverse reinforcement.

D E S I G N C O N S I D E R A T I O N S

Moment of ResistanceThe moment of resistance of the composite section (neutral axis within the web) is given below:

Ms = capacity of the steel section onlyD = steel section depth Dslab = concrete slab depth Rc = compressive force in concrete flangeRw = force in the web of the steel section

beff

Dslab

DP. N.A

Py

Py

Rc = 0.45 x fcu; x beff x D slab

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B I S O N P R E C A S T F L O O R I N G

S P E C I F I C A T I O N

REGISTRATION No. FM 11

CSBD / 1 / 01Designed and Produced by Raj Nagi Design ConsultancyTel 01628 638395 E-mail design@rajnagi.com

MANUFACTURE

Bison Floors are manufactured by the long line prestressed method using slip form techniques.The units are cast on heated steel beds withinan enclosed factory environment.

Bison units are manufactured in varying depthsand to a nominal width of 1200mm.

Cross-sectional tolerances are within the limitsset out in clause 6.2.8.3 of B.S. 8110: 1997.Length tolerances are + 20mm.

Bison units have an upward camber due toprestressing as described in clause 6.2.8.4 of B.S. 8110: 1997.

Concrete surface finish to soffits is Type Afinish as described in clause 6.2.7.3 of B.S.8110: 1997.

Sides and top surfaces are ‘as extruded’ asdescribed in table 5.5 of B.S. 8110: 1997.

A complete Bison Precast FlooringSpecification is available upon request.

SPECIFIC MANUFACTURINGREQUIREMENTS

Formation of four number 500mm long elongated slots in the hollow core units.

Formation of standard AN type notch to the endsof the units where design requirements determine.

Provision of drain points to remove any accumulated water from the cores.

INSTALLATION-HEALTH ANDSAFETY

The health and safety requirements for the site works are detailed within the Code ofPractice for The Safe Erection of PrecastConcrete Flooring.

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Lateral instability of the steel beams duringconstruction. For UB and UC sections it is recommended that any beam greater than 8.0min length is provided with temporary lateralrestraint to the top flange.

For slender beams such as Castellated, Cellformor Fabsec beams this is further reduced. Adviceshould be sought from the appropriate fabricator.

Bearing of the units in the temporary case.

QUALITY ASSURANCE

All Bison manufacturing plants are members of the B.S.I. Registered Firms Scheme forQuality Assurance to B.S. EN ISO 9001: 1994for the design and manufacture of precast concrete products.

Membership of the scheme ensures that allprocedures and disciplines relevant to thedesign and manufacturing processes are subjectto the independent approval and periodicreview by the British Standards Institution.

All Bison U.K. factories have been assessedby the British Standards Institution (B.S.I.)and awarded Certificates of Assessed Capabilityunder the scheme covering Quality Assurancefor the manufacture of precast concrete floors.

As a customer, you can be sure that all aspectsof our production, design detailing and qualitycontrol have been independently inspected andhave achieved the high level of competenceand quality required by the British StandardsInstitution.

The company maintains a policy of continuousdevelopment, and reserves the right to changespecification and details without prior notice.

PRECAST STAIRCASES

BEAM AND BLOCK FLOORS

STRUCTURES

BISON CONCRETE PRODUCTS LIMITEDMillennium CourtFirst Avenue, Centrum 100Burton Upon Trent, DE14 2WRFAX 01283 544900 TEL 01283 495000E-MAIL concrete@bison.co.uk

HOLLOW CORE FLOORS

UPPER FLOORS IN HOUSES