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Copy of How to achieve LONG SPAN in Steel Construction?

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Goli Noush

on 4 January 2015

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Transcript of Copy of How to achieve LONG SPAN in Steel Construction?

One way to classify long-span structures
How to achieve
LONG SPAN Construction

most common structural material due to its strength to weight ratio, ease of fabrication and cost.
Long span single storey structures have a wide variety of uses
A wide range of different structural systems for long span sheds
Steel is by far the most common structural material used in the construction
There has been an increasing demand for longer column free spaces to provide maximum flexibility of the interior space.
The structure can be clad in a variety of ways, with profiled steel sheeting a common choice.
The design of large sheds provides a wealth of opportunities for the designer to explore technology.
Large flexible spaces can be provided to suit a wide range of uses.
Concluding Summary
Generally long spans using steel result in merits of:
lightness, flexible
column free internal spaces
reduce substructure costs
reduce steel erection times
Traditional approach is truss system, which organizes the steel pipes with triangular units, and systematic joint systems have been developed.
How long is long-span for buildings
Structure with span larger than 20m can be regarded as long span structure for this span is usually unable to be achieved by ordinary RC structure.
Long Span Structures
These systems incorporate facility for integration of large building services
The merit of each of the below systems depends on span, cost, degree of service integration, future adaptability.
Cellular Beams
Perforation lighten sections and provide routes for building services.
Usual maximum span
Beam depth
15 m
Haunched Beams
Rigid connections reduce overall beam depth.
Usual maximum span
Beam depth
18 m
Fabricated Beams
The section is fabricated from three plates welded together to form an I-section and it is to allow for service integration.
Usual maximum span
Beam depth
15 m
Composite Trusses
Trusses connected to floor slab using welded shear studs. Trusses may use tee, angle or hollow sections.
Usual maximum span
Beam depth
30 m
Stud Girders
Short beam section are welded to the top of beams and support the floor slab. Services may pass through voids.
Usual maximum span
Beam depth
15 m
Tapered Beams
Tapered sections provide service zone adjacent to columns.
Usual maximum span
Beam depth
25 m
Alternative tapered beam profiles:
Structural Options
Large single volume sheds can be conveniently classifies according to their structural forms.
1. Beam Structures
Consisting of beams supported on columns, are of common usage both in single span and multi-span form.
Advantage - lend themselves to prefabrication in elements for ease of transportation and site erection.
Flat beam structure is most appropriately used where the minimum volume of space is required within the desired clear height.
Beams may be solid web or truss forms.
Eg. Mies Van der Rohe's Crown Hall building
2. Portals & Arches
Arches, which can take a variety of forms, are efficient structures for long span roofs.
This traditional arched form of construction provided the first long span railway structures and airship hangars.
Portal frame structures, where standard beam sections are bolted together with a range of joint types.
Different spans and clear heights are achieved from a set of standard components with the advantages of speed and economy.
It started in the 19th century with the advent of the railways.
In demand for long span enclosures at a time when the technology of cast iron structures was sufficiently advanced.
Portal Frame Structures
Modern Art Glass office and warehouse at Thamesmead
Waterloo Station by Nicholas Grimshaw and Partners
3. Masted Structures
Used in bridge building and tented structures for decades.
From the need for extremely high levels of mechanical services plants which were housed in a gantry above the circulation spine.
Eg. Fleetguard Distribution Centre in Quimper, Brittany
4. Space Frames
Three-dimensional assemblies of linear members in which the interconnections are such that a load at any point is distributed in all directions.
Member sizes can be decreased which made them an efficient and economic solution to long spans.
Can take the form of flat double-layer grid structures or braced domes and vaults.
Eg. Louisiana Superdome in New Orleans
5. Umbrella Structures
Umbrella or Tree Structures, the roof cantilevers from central column and can be repeated and joined to other similar assemblies at each or any side to form a continuous structure.
The 'trees', which are 21m tall, consist of a cluster of 457mm diameter steel tubes which branch out at the 13m high level to support a shallow dome covering an area of 18mx18m.
Eg. Stansted Airport by Foster Associates
of Long Span Structure
Cast Iron
Wrought Iron
In the year 1850s, Britain saw the construction of new age of architectural engineering.
Crystal Palace
Paddington Station

In the early 20th century, structural requirements for lighter-than-air crafts encouraged the development of lightweight structures.
The need for economical, long span, large volume sheds which resulted in the construction of a number of elegant functional steel buildings of awe inspiring proportions.
The largest of these was the Goodyear Airdock at Akron Ohio, in 1929, with an elegant parabolic three pinned arch structure spanning 99m. The pure shape was derived from wind tunnel tests designed to reduce air turbulence around the doors which could affect the manoeuvring of the great airships.
The need for large covered spaces to house swimming pools, indoor sports, conference centres and huge arenas has also provided a challenge to architects and engineers to create efficient economical and appropriate structural enclosures.
Why use Steel?
1. Dead load
2. Live load
3. Wind load
4. Stress created by temperature differences
5. Stress created by other form of disruption
including ground movement, vibration,
deformation or earthquake
Loads acting onto
a structural systems
1. All reinforced concrete including precast
2. All metal (e.g. mild-steel, structural steel,
stainless steel or alloyed aluminium,
3. All timber
4. Laminated timber
5. Metal/RC combined
6. Plastic-coated Textile material
7. Fiber reinforced plastic
Materials suitable for various forms of long span structure
1. Insitu RC, tensioned
2. Precast concrete, tensioned
3. Structural steel – erected on spot
4. Structural steel – prefabricated and
installed on spot
5. Portal frame – insitu RC
6. Portal frame – precast
7. Portal frame – prefabricated steel
Common Structural Forms for Long Span Building Structures
Form active systems
Vector active systems
Surface active systems
Section active systems
. . . are systems of flexible, non-rigid matter, in
which the redirection of forces is effected by
particular form design and characteristic
form stabilization
Example of structures:
1. Cable structures
2. Tent structures
3. Pneumatic structures
4. Arch structures
... are systems of short, straight lineal members, in which the redirection of force is affected by vector partition, i.e. by multi-directional splitting of single force simply to tension or compressive elements.
Example of structures:
Flat trusses
Curved trusses
Space trusses
. . . are systems of rigid, solid, linear
elements, in which redirection of forces
is effected by mobilization of sectional forces
Example of structures:
1. Beam structures
2. Frame structures
3. Slab structures
. . . are systems of flexible or rigid planes
able to resist tension, compression or
shear, in which the redirection of forces
is effected by mobilization of sectional
Example of structures:
1. Plate structures
2. Folded structures
3. Shell structures
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