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Item of work truss

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ferrocement trusses

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Item of work truss

  1. 1. Steel as construction material
  2. 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.
  3. 3. Steel used as supporting buttresses and extended columns *BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON
  4. 4. canopy *BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON
  5. 5. Steel used as permanent bracing between two building, extended form of which supports the roof *BUILDING- BAUMSCHULENWEG CREMATORIUM, BERLIN
  6. 6. 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
  7. 7. Dynamic columned wall completely made of steel *BUILDING- MEXICAN EMBASSY, BERLIN, GERMANY
  8. 8. Same framework acting as piers and truss *BUILDING- BRITISH RECORD INDUSTRY TRUST(BRIT) SCHOOL, LONDON
  9. 9. 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.
  10. 10. •Long span •Lightweight •Reduced deflection (compared to plain members) •Opportunity to support considerable loads. THE MAIN REASONS FOR USING TRUSSES ARE:
  11. 11. • 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
  12. 12. SOME COMMONLY USED TRUSSES ARE: PRATT TRUSS ('N' TRUSS) WARREN TRUSS NORTH LIGHT TRUSS SAW-TOOTH TRUSS FINK TRUSS
  13. 13. • 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
  14. 14. 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
  15. 15. • 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
  16. 16. • 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
  17. 17. BASIC MEMBERS OF A STEEL TRUSS
  18. 18. TYPES OF TRUSS MEMBERS
  19. 19. • 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
  20. 20. 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.
  21. 21. 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
  22. 22. • 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
  23. 23. • 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.
  24. 24. 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
  25. 25.  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

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