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Industrial building

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Industrial building

  2. 2. Industrial building • Any building structure used by the industry to store raw materials or for manufacturing products of the industry is known as an industrial building. • Industrial buildings are generally used for steel plants, automobile industries, utility and process industries, thermal power stations, warehouse, assembly plants, storage, garages, etc.
  3. 3. Factors considered while selecting site for industrial building • Site should be located on an arterial road. • Local availability of raw material. • Facilities like water supply, electricity • Topography of an area • Soil conditions with respect to foundation design • Waste disposal facilities • Transportation facilities • Sufficient space for storage of raw materials
  4. 4. Major Component of Industrial Unit:
  5. 5. • Roof Sheet: Material used to cover the shed is known as roof shed. • Roof trusses: A structure that is compound of a number of line members pined connected at ends to form a triangular form work is called truss.
  6. 6. Eave strut purlin bracinggirt
  7. 7. • Purlin: A member supported on the panel points of two consecutive roof truss is called purlin. • Girts: Girts are the secondary structural member which provide support to roof and wall covering and also transferred wind load from wall material to primary frame. • Eave strut: The member located at the intersection of roof and exterior wall is known as eave strut.
  8. 8. • Bracing: A member which transfer horizontal load from the frame to the foundation is known as bracing. • Wind Bracing: Two roof trusses are connected by cross members to stabilize it against the action of wind, such a members are called wind bracing.
  9. 9. Componentsof roof truss:
  10. 10. Points to be considered while planning and designing of industrial building 1. Selection of roofing and wall materials
  11. 11. Roofing Material: • Roofing material is used to cover the roof of truss. • In India, corrugated galvanized iron (GI) sheets are usually adopted as coverings for roofs and sides of industrial buildings. • Light gauge cold-formed ribbed steel or aluminium decking can also be used. • Sometimes asbestos cement (AC) sheets are also provided as roof coverings owing top their superior insulating properties.
  12. 12. • Galvanized Iron Sheet: Galvanized iron sheets are made by black sheets rolled from good quality low carbon mild steel. For corrugated G.I. sheets, the purlin space may vary from 1.5 to 1.75 m. • End overlap of 150 mm is required.
  13. 13. • Asbestos Cement Sheets: Asbestos cement sheets do not decay because of atmospheric action. • These sheets are available in 1.75 m, 2.0 m and 3.0 m lengths. These are manufactured in 6 mm and 7 mm thickness. • For asbestos cement sheet, the purlin space may be vary from 1.4 m for 6 mm sheet and 1.6 m for 7 mm sheet.
  14. 14. • In selection of wall system, the designer should consider the following areas: • Cost • Interior surface requirements • Aesthetic appearance • Acoustic and dust control • Maintenance • Ease and speed of erection • Insulating properties • Fire resistance
  15. 15. 2. Selection of bay width • A bay is defined as the space between two adjacent bents. The roof truss along with the columns constitutes a bent. • An industrial building may have a single span or multiple spans
  16. 16. • In most cases, the bay width may be dictated by owner requirements. Gravity control generally control the bay size • For crane buildings (light or medium cranes), bays are approximately 4-8 m may be economical because of the cost of the crane gantry girder
  17. 17. 3. Selection of structural framing system
  18. 18. • For the purpose of structural analysis and design, industrial buildings are classified as: • Braced Frames • Unbraced frames • In braced buildings, the trusses rest on columns with hinge type of connections and the stability is provided by bracings in three mutually perpendicular planes. • Braced frames are efficient in resisting the loads and do not sway.
  19. 19. • Unbraced frames: They are in the form of portal frames and are used mostly, distinguished by its simplicity, cleanliness and economy. • The frames can provide large column free areas, offering maximum adaptability of the space inside the building. Such large span buildings require less foundation and eliminate internal columns and drainage.
  20. 20. • They are advantageous for more effective use of steel then in simple beams, easy extension at any time and ability to support heavy concentrated point loads. • The disadvantages include really high material unit cost and susceptibility to differential and temperature stresses. In addition, these frames produce horizontal reaction on the foundation, which may be resisted by providing a long tie beam or by designing the foundation for this horizontal reaction
  21. 21. 4. Roof trusses
  22. 22. CONFIGURATION OF TRUSSES Pitched Roof Trusses : • Most common types of roof trusses are pitched roof trusses wherein the top chord is provided with a slope in order to facilitate natural drainage of rainwater and clearance of dust/snow accumulation. • These trusses have a greater depth at the mid-span. Due to this even though the overall bending effect is larger at mid- span, the chord member and web member stresses are smaller closer to the mid-span and larger closer to the supports.
  23. 23. • The typical span to maximum depth ratios of pitched roof trusses are in the range of 4 to 8, the larger ratio being economical in longer spans. Pitched roof trusses may have different configurations.
  24. 24. • In Pratt trusses web members are arranged in such a way that under gravity load the longer diagonal members are under tension and the shorter vertical members experience compression. This allows for efficient design, since the short members are under compression.
  25. 25. • However, the wind uplift may cause reversal of stresses in these members and nullify this benefit. The converse of the Pratt is the Howe truss, This is commonly used in light roofing so that the longer diagonals experience tension under reversal of stresses due to wind load.
  26. 26. Fink trusses are used for longer spans having high pitch roof, since the web members in such truss are sub-divided to obtain shorter members.
  27. 27. Fan trusses are used when the rafter members of the roof trusses have to be sub-divided into odd number of panels
  28. 28. A combination of fink and fan can also be used to some advantage in some specific situations requiring appropriate number of panels. Mansard trusses are variation of fink trusses, which have shorter leading diagonals even in very long span trusses, unlike the fink and fan type trusses.
  29. 29. • The economical span lengths of the pitched roof trusses, excluding the Mansard trusses, range from 6 m to 12 m. The Mansard trusses can be used in the span ranges of 12 m to 30 m.
  30. 30. Types of truss Span used Pitched fink truss Upto 9 m (economical) Pratt truss 6 to 15 m Compound fink truss Longer span upto 28 m Simple fan truss 12 m Compound fan truss Upto 24 m
  31. 31. 5. Purlins, girts and sag rod
  32. 32. • Purlin support roof sheeting, and loads from the sheeting are transferred to the purlins. • The loads acting on the purlins are weight of roof covering and fixtures self-weight of purlin, live load from sheeting, snow load, and wind load
  33. 33. Sections used as purlins: 1.Angle Purlins: It is used in small shops when spacing of roof truss is between 3 to 5 m.
  34. 34. •Channel Purlins: It is used for medium shops, when spacing of roof truss is between 4 to 6 m.
  35. 35. • Beam Purlin: It is used for heavy shops, when spacing of roof truss is between 6 to 8m.
  36. 36. Spacing of Purlin: • The spacing of purlin depends largely on the maximum safe span of the roof covering and glazing sheets. Hence they should be less than or equal to their safe span when they are directly placed on purlins. • Thus for corrugated GI sheet, the purlin spacing may vary from 1.5 to 1.75 m, and for corrugated AC sheets, it is limited to 1.4 m, for 6 mm thick sheets, and 1.6 m, for 7 mm thick sheets.
  37. 37. • For larger spans, if the configuration of the truss is such that it is not feasible to place purlin at the nodes of upper chords, the purlin are placed between the nodes, thus introducing bending moment in the upper chords, in addition to the compressive force due to truss action. • Hence in this case, the weight of the truss may be increased by about 10-15 %. Therefore, it is preferable to place purlin at the nodal point of the truss, so that the upper chord member are subjected to only direct compression
  38. 38. 6.Bracing system to resist lateral loads
  39. 39. 7. Gantry girders, columns, base plates and foundation
  40. 40. Loads on trusses • The main loads on trusses are dead, imposed and wind loads. • The dead loads is due to sheeting or decking and their fixtures, insulation, false ceiling, weight of purlins and self weight. This load may range from 0.3 to 1.0 kN/m2 Page no 30, table 1 IS 875-1
  41. 41. • The weights of purlins are known in advance as they are designed prior to the trusses. Since the weight of truss is small compared to total DL,LL, considerable assumptions is taken in account for weight of truss and it will not have a great impact on the stresses in the various members.
  42. 42. • For Live load upto 2 kN/m2, following formula is used to get the approximate value of weight of truss • W =20 + 6.6L (w=wt of truss in N/mm2, L=span in m) • For welded trusses, the self wt of truss is w=53.7 + 0.53A (A= area of one bay). • For LL > 2 kN/m2, the value of w may be multiplied by the ratio of actual live load in kN/m2/2
  43. 43. Load calculations for design • The following load combinations of loads are considered when there is no crane load • DL + LL • DL + Snow load • DL + WL (normal to ridge or parallel to ridge whichever is severe) • DL + LL + WL(most critical)
  44. 44. • The weight of bracings may be assumed to be 12-15 N/m2 of the plan area. • The imposed load on roofs will be as per IS-875-II. Page no 15, table 2 IS 875-2
  45. 45. • The wind load should be calculated as per IS - 875-III • Since EQ load depends on the mass of the building, earthquake load do not govern the design of light industrial buildings. Thus wind load governs the design of normal trussed roofs
  46. 46. Thank you…