ferrocement trusses

1. Steel as
construction
material

2. • 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.

4. Steel used as supporting buttresses and extended columns
*BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON

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

6. Steel used as
permanent bracing
between two building,
extended form of which
supports the roof
*BUILDING- BAUMSCHULENWEG CREMATORIUM,
BERLIN

7. 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

8. Dynamic columned wall completely made of steel
*BUILDING- MEXICAN EMBASSY, BERLIN, GERMANY

9. Same framework acting as piers and truss
*BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON

10. 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.

12. •Long span
•Lightweight
•Reduced deflection (compared to plain members)
•Opportunity to support considerable loads.
THE MAIN REASONS FOR USING TRUSSES ARE:

13. • 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

14. SOME COMMONLY USED TRUSSES ARE:
PRATT TRUSS ('N' TRUSS) WARREN TRUSS
NORTH LIGHT TRUSS SAW-TOOTH TRUSS
FINK TRUSS

15. • 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

16. 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

17. • 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

18. • 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

19. BASIC MEMBERS OF A STEEL TRUSS

20. TYPES OF TRUSS MEMBERS

21. • 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

22. 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.

23. 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

25. • 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

26. • 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.

27. 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

28.  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