Steel as construction material

• Steel can be considered as a skeleton for every

structure.

• Most kind of structures {made of any material}, requires

steel.

• But steel structures are most easy to build, maintain and

use.

• They can be easily dismantled and recycled.

• Steel can be used in different things.

• For large scale structures steel is much more feasible

and economical than any other material.

Steel used as supporting buttresses and extended columns

*BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON

canopy

*BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON

Steel used as permanent bracing between two building, extended form of which supports the roof

*BUILDING- BAUMSCHULENWEG CREMATORIUM,

BERLIN

Steel used as permanent support and bracing to the facade

Cathédrale Nôtre Dame de la Treille, Lille, France Hotel de las Artes, Barcelona, Spain, Skidmore Owings & Merril

Dynamic columned wall completely made of steel

*BUILDING- MEXICAN EMBASSY, BERLIN, GERMANY

Same framework acting as piers and truss

*BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON

ITEM OF WORK: STEEL TRUSS

• A truss is essentially a triangulated system of straight interconnected structural elements.

• The most common use of trusses is in buildings, where support to roofs, the floors and internal loading such as services and suspended ceilings, are readily provided.

• Trusses are also commonly used in temporary as well as non habitable places such as parking area, veranda, stadiums, railway station, etc.

•Long span

•Lightweight

•Reduced deflection (compared to plain members)

•Opportunity to support considerable loads.

THE MAIN REASONS FOR USING TRUSSES ARE:

• Trusses comprise assemblies of tension and compression

elements.

• Under gravity loads, the top and bottom chords of the truss

provide the compression and tension resistance to overall

bending, and the bracing resists the shear forces.

• A wide range of truss forms can be created.

• Each can vary in overall geometry and in the choice of the individual elements.

WHY VARIOUS TYPES OF TRUSSES ARE USED?

* FROM WEB- http://www.all-concrete-cement.com/steel-roof-truss-design.html

SOME COMMONLY USED TRUSSES ARE:

PRATT TRUSS ('N' TRUSS) WARREN TRUSS

NORTH LIGHT TRUSS SAW-TOOTH TRUSS

FINK TRUSS

• For efficient structural performance, the ratio of span to truss

depth should be chosen in the range 10 to 15.

• The architectural design of the building determines its

external geometry and governs the slope(s) given to the top

chord of the truss.

• The intended use of the internal space can lead either to the

choice of a horizontal bottom chord, e.g. where conveyors

must be hung under the chord, or to an inclined bottom

chord, to allow maximum space to be provided.

GENERAL GEOMETRY

For an efficient layout of the truss members between the

chords, the following is advisable:

•The inclination of the diagonal members in relation to the

chords should be between 35° and 55°

•Point loads should only be applied at nodes

•The orientation of the diagonal members should be such that

the longest members are subject to tension (the shorter ones

being subject to compression).

* FROM WEB- http://www.steelconstruction.info/Trusses

• Many types of sections are available for making a steel truss.

• Choice of members depends on the magnitude of the internal forces, ease of

connections between members, aesthetics and any necessity to connect prefabricated truss sections on site.

• For smaller spans, tee sections are frequently used for chords, with angles used

as internal members.

• Back-to-back angles or channels may be used for longer spans or heavier loads,

with a gusset plate used at nodes to connect the members.

TYPES OF TRUSS SECTIONS

TYPICAL ELEMENT CROSS SECTIONS FOR LIGHT BUILDING TRUSSES

• For large trusses and heavy loads, typically found in transfer trusses in

buildings, members may be rolled sections.

• For many exposed trusses, hollow sections are chosen for their structural

efficiency and for aesthetic reasons.

• As part of the truss design, it is essential to verify the resistance of the joints (in

accordance with BS EN 1993-1-8) as the joint design may dominate member

selection and final truss geometry.

• Members should be selected carefully to avoid expensive strengthening of

trusses fabricated from hollow sections

DIFFERENT TYPES OF STEEL SECTION USED IN TRUSSES

* FROM WEB- http://www.steelconstruction.info/Trusses

BASIC MEMBERS OF A STEEL TRUSS

TYPES OF TRUSS MEMBERS

• Two types of structural elements, struts and ties, are associated with

bracing in trusses.

• Struts are inserted to resist compression. Ties resist tension.

• When engineered correctly, a truss is considered an ideal means to handle

loads over a long period of time without yielding, deforming or breaking.

• In the case of bridges, trusses may also span large distances because they

can be built or prefabricated in sections.

• A truss usually have 3 chord members

ELEMENTS OF A STEEL TRUSS

MEMBERS OF A STEEL TRUSS

TIE BEAM

It's defined as a horizontal structural

member that supports vertical loads. It’s the

member at the base which holds the above parts and transfer the loads to columns.

GUSSET PLATE

A gusset plate connects two or more structural members along one plane. The plates are

designed to minimize bending at the

connections, which enables the members to

do their job resisting tension or compression.

PURLIN

These are secondary, horizontal members

laid out to hold the sheeting that will be laid

out on the roof. Purlins are made of lighter-

gauge steel than girders, since they're not

used to hold up heavy loads.

Decking is a flat surface that sits atop the

floor and roof joists in a building or other

structure. Multiple sheets of metal, usually

corrugated, are interlock or fastened and welded together.

DECKING

• For all the types of member sections, it is

possible to design either bolted or welded

connections.

• Generally in steelwork construction, bolted site

splices are preferred to welded splices for

economy and speed of erection.

• Where bolted connections are used, it is

necessary to evaluate the consequences of

'slack' in connections. In order to reduce these

consequences (typically, the increase of the

deflections), solutions are available such as use

of preloaded bolts.

TYPES OF JOINTS/ JOINERY

• Hollow sections are typically connected

by welding whilst open sections are connected

by bolting or welding, which will usually involve the

use of gusset plates.

• Small trusses which can be transported whole from

the fabrication factory to the site, can be entirely

welded.

• In the case of large roof trusses which cannot

be transported whole, welded sub-assemblies are

delivered to site and are either bolted

or welded together on site.

• In light roof trusses entirely bolted connections are

less favoured than welded connections due to the

requirement for gusset plates and their

increased fabrication costs.

ESTIMATED PRICES

• Steel prices - 45-50 Rs/Kg

• fabrication charges - 15-20 Rs/Kg

• Labour charges - 30 Rs/sq. feet

• Roofing charges depends upon the type of roofing.

• For prefabricated members, it takes around 1-2 hours to assemble the truss of a

standard size of 5m* 5m.

*FROM MARKET SURVEY

http://www.steelconstruction.info/Trusses

http://www.all-concrete-cement.com/steel-roof-truss-

design.html

http://internationalsteelframing.com/products-and-

services/products/

http://www.jfba.com/truss-design-estimating.htm

http://www.steel-insdag.org/teachingmaterial/chapter27.pdf

REFERENCES