COMPOSITE STEEL BEAM DESIGN
SPEED AND STRENGTH
INTRODUCTION
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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T H E A D VA N T A G E S
Steel Economy
The use of hollow core and solid slabs for composite
steel beam design provides a reduction in the total
tonnage of structural sections compared with the
use of non composite and composite metal deck
steel solutions.
Immediate Unpropped Working Platform
Once a precast floor is erected, it is immediately
available as a working platform. Steel deck systems
by comparison can present problems in achieving
level surfaces whilst concrete is poured and in
providing access whilst in the propped condition.
Speed of Erection
Time consuming activities such as propping,
shuttering and concrete pouring are virtually
eliminated.
No Propping
Propping is not required with hollow core slabs
designed compositely into a steel framed building.
Compare this with the large amount of propping
required with fully insitu and semi-insitu floor
systems.
Using a precast floor, a large volume of work is carried
out off site and saves what can be a complex and
time consuming site operation subject to the vagaries
of the climate.
Diaphragm Action
Precast floor slabs are structurally grouted to provide
a floor with full diaphragm action as required in
most multi–storey frames. This can be achieved
without a structural topping.
Reduced Site Operations
The use of hollow core and solid slabs in composite
steel beam design greatly reduces the amount of
insitu concrete work on site.
Finished Soffits
Precast floors are manufactured on high quality
steel beds and are suitable in appropriate cases
for direct decoration.
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 a
building and consequently in site programme time.
Factory Engineered Components
Precast floors are factory produced, being
manufactured in an environment which is more
readily controlled than a building site. Quality
control systems are properly implemented and
are independently examined on a regular basis
under the British Standards Institution Quality
Assurance Scheme.
The provision of factory welded shear studs
removes this operation from the site critical path.
Optimisation of Shear Stud Design
The use of hollow core and solid slabs for composite
steel beam design allows the optimisation of shear
stud design due to the lack of restriction in positioning
the shear studs.
Product Application
Composite steel beam design offers an economic
solution whenever a steel frame is being considered.
It has been proved successful in the design and
construction of office, commercial, industrial, hotel,
stadia and car park developments.
Elimination of Deflection
The use of hollow core and solid slabs in composite
steel beam design eliminates the difficulties experienced with local deflection of a metal deck solution
between steel beam supports.
Raised Access Floor
No additional finishes are required to the top surface
of the hollow core units prior to the installation of a
raised access floor.
Fire Resistance
Standard precast floors can be supplied with a fire
resistance of up to 2 hours.
2
COMPOSITE STEEL BEAM DESIGN
Definition
Composite Steel Beam Design is the use of hollow core and solid slabs together
with insitu infill in conjunction with welded studs onto steel beams to enable
the slabs and steel beams to act compositely together enhancing the load capacity
of the steel beams.
Research and Development
The research and development of the application of precast hollow core and
solid slabs to the design of composite steel beams is the result of several
research projects undertaken since 1993. These have been supported by the
Engineering and Physical Sciences Research Council, the Precast Flooring
Federation 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 the
statistical basis. This provides the data for the Design Guide undertaken by
the Steel Construction Institute and the Precast Flooring Federation, supported
by 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.
The Components
Design Support
Bison Concrete Products Limited are committed to providing the technical
support together with computer software enabling engineers to maximise their
design options for this product.
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D E S I G N C O N S I D E R AT I O N S
The design procedures, to B.S. 5950 Part 3, described within the research and development projects have
been adopted in the available software and are summarised below:
Shear Stud Capacity
The design shear resistance of the studs is the lesser of the following formulae:
?
d
fu
= 0.2 ( h/d+1) h = height of the stud.
= is the diameter of the shank of the stud.
= 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) ≤ 1.0
and 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.
Effective Width of Compression Area
fcu
ø
fy
g
=
=
=
=
insitu concrete strength
diameter of reinforcement
characteristic strength of the reinforcement
gap between ends of precast units
With a maximum beff of the actual width.
Rc = 0.45 x fcu; x beff x D slab
beff
D slab
P. N.A
P. N.A
Py
D
Py
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D E S I G N C O N S I D E R AT I O N S
Moment of Resistance
The moment of resistance of the composite section (neutral axis within the web)
is given below:
Ms =
D =
Dslab =
Rc =
Rw =
capacity of the steel section only
steel section depth
concrete slab depth
compressive force in concrete flange
force in the web of the steel section
Rc = 0.45 x fcu; x beff x D slab
beff
D slab
Py
P. N.A
D
Py
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.
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BISON PRECAST FLOORING
S P E C I F I C AT I O N
MANUFACTURE
3.2 Lateral instability of the steel beams during
construction. For UB and UC sections it is
recommended that any beam greater than 8.0m
in length is provided with temporary lateral
restraint to the top flange.
1.1 Bison Floors are manufactured by the long line
prestressed method using slip form techniques.
The units are cast on heated steel beds within
an enclosed factory environment.
3.3 For slender beams such as Castellated, Cellform
or Fabsec beams this is further reduced. Advice
should be sought from the appropriate fabricator.
1.2 Bison units are manufactured in varying depths
and to a nominal width of 1200mm.
1.3 Cross-sectional tolerances are within the limits
set out in clause 6.2.8.3 of B.S. 8110: 1997.
Length tolerances are + 20mm.
3.4 Bearing of the units in the temporary case.
1.4 Bison units have an upward camber due to
prestressing as described in clause 6.2.8.4
of B.S. 8110: 1997.
4.1 All Bison manufacturing plants are members
of the B.S.I. Registered Firms Scheme for
Quality Assurance to B.S. EN ISO 9001: 1994
for the design and manufacture of precast
concrete products.
QUALITY ASSURANCE
1.5 Concrete surface finish to soffits is Type A
finish as described in clause 6.2.7.3 of B.S.
8110: 1997.
Membership of the scheme ensures that all
procedures and disciplines relevant to the
design and manufacturing processes are subject
to the independent approval and periodic
review by the British Standards Institution.
1.6 Sides and top surfaces are ‘as extruded’ as
described in table 5.5 of B.S. 8110: 1997.
A complete Bison Precast Flooring
Specification is available upon request.
All Bison U.K. factories have been assessed
by the British Standards Institution (B.S.I.)
and awarded Certificates of Assessed Capability
under the scheme covering Quality Assurance
for the manufacture of precast concrete floors.
SPECIFIC MANUFACTURING
REQUIREMENTS
2.1 Formation of four number 500mm long
elongated slots in the hollow core units.
As a customer, you can be sure that all aspects
of our production, design detailing and quality
control have been independently inspected and
have achieved the high level of competence
and quality required by the British Standards
Institution.
2.2 Formation of standard AN type notch to the ends
of the units where design requirements determine.
2.3 Provision of drain points to remove any
accumulated water from the cores.
The company maintains a policy of continuous
development, and reserves the right to change
specification and details without prior notice.
INSTALLATION-HEALTH AND
SAFETY
3.1 The health and safety requirements for the
site works are detailed within the Code of
Practice for The Safe Erection of Precast
Concrete Flooring.
REGISTRATION No. FM 11
CSBD / 1 / 01
Designed and Produced by Raj Nagi Design Consultancy
Tel 01628 638395 E-mail [email protected]
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HOLLOW CORE FLOORS
UPPER FLOORS IN HOUSES
BEAM AND BLOCK FLOORS
PRECAST STAIRCASES
STRUCTURES
BISON CONCRETE PRODUCTS LIMITED
Millennium Court
First Avenue, Centrum 100
Burton Upon Trent, DE14 2WR
FAX 01283 5 4 4 9 0 0
T E L 01283 4 9 5 0 0 0
E-MAIL [email protected]