Presentation is loading. Please wait.

Presentation is loading. Please wait.

Roof Trusses. Definition Load Transferred Load Transferred Load not Transferred.

Similar presentations


Presentation on theme: "Roof Trusses. Definition Load Transferred Load Transferred Load not Transferred."— Presentation transcript:

1 Roof Trusses

2 Definition Load Transferred Load Transferred Load not Transferred

3 Truss Types Trusses are categorised into 3 groups depending on the shape of the top chord 1.Triangular Roof Trusses 2.Crescent roof Trusses 3.Other Types

4 Triangular Roof Trusses Simple Triangular geometric shape Web Bracing Straight Top Chord

5 Triangular Roof Trusses

6 Crescent Roof Trusses Top Chord is manufactured with a curved top chord The Harbour bridge is a good example

7 Other Types Top Chords may be parallel – such as floor joist trusses Or they may be nearly parallel – such as bridges

8

9 Terminolgy

10

11 Roof Truss Members

12 Roof Truss Panel Points

13 Roof Truss Stress Types

14 Parallel Chord Trusses Top Chord & Bottom Chord are parallel Used as Rafters Advantages Lighter Larger Spans Allow for easy access for services Disadvantages Cannot be site modified

15 Parallel Chord Trusses Top Chord & Bottom Chord are parallel Used as Rafters Advantages Lighter Larger Spans Allow for easy access for services Disadvantages Cannot be site modified Generally Deeper

16 Parallel Chord Trusses

17 Truss Manufacture Designed by Structural Engineer No Site Modification or repair without engineer supervision Trusses manufactured in controlled factory conditions to ensure design is strictly followed

18 Truss Manufacture Nailing Plates – Claw Type, only suitable for use with a press – Knuckle type, can be nailed with a hammer or pressed

19 Truss Manufacture Member Sizes must be specified by engineer Trusses Manufactured in factory in controlled environment Members are assembled and cut in jigs and presses

20

21 Camber Trusses are manufactured with camber in the bottom chord 1.To allow for calculated deflection while dead loads such as Roof Covering & Ceiling Linings 2.Bottom chord should not be supported between supports, unless specifically designed

22 Transfer of Loads Internal Wall Min 12 Clear Click to show load flow on correctly installed trusses Compression Load Tensile Load to Counteract Compressive Load No load in this Area

23 Transfer of Loads Bottom Chord bearing on Internal Wall Click to show load flow on incorrectly installed trusses Load transmits Horizontally to wall. Bottom Chord is not designed to take horizontal load and will fail

24 Support to Trusses Top Plates Based on AS 1684 Span Tables As no internal support walls, spans are large Loads imposed on top plates are greater than conventional roofs

25 Top Plates Option1 Using Nominal Thickness Top Plates (i.e. 90 x 35) Place Studs directly under trusses

26 Top Plates If Trusses are not placed directly over studs Top Plates may be overloaded and deflect and/or fail

27 Top Plates Option 2 Increase Top Plate as per 1684

28 Top Plates & Girder Truss It is always good practice to have studs as per concentrated loads beneath a girder truss

29 Lintels Similarly Lintels should be sized according to AS 1684 As the spans are larger than a conventional roofs, large members may be required An options may be to use C & Z metal lintels

30 Z Lintels

31 Lifting Roof Trusses Never lift by the Apex This will damage the roof trusses

32 Lifting of Trusses Note That lifting is done at Panel Points

33 Bundle Lifting Ensure that trusses are tied or banded together at base

34 Storage of Trusses Trusses should be inspected on delivery No site repairs with out design engineers supervision Stored flat on timber dunnage

35 Carrying of Trusses

36 Installation of Trusses

37 Erection of Trusses

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59 Note – All Trusses need to Temporarily Braced during Installation The purpose of temporary bracing is to hold the trusses plumb & true until permanent bracing is installed

60 Erection Tolerances

61

62 Complex Roofs Trusses can be made to suit just about any roof shape

63 Complex Roofs Trusses can be made to suit just about any roof shape

64 Truss Layout

65 Trussed Hip Roofs Jack End Truss

66 Hip Truss

67 Truncated Girder Truss Placed at position determined by Engineer Will take load of Jack Truss, Hip Truss & Creeper Truss Designed to take more load than other trusses

68 Truncated Truss Placed between girder truss and gathering point Important to be placed at specified spacing at they will increase in height to match the hip end Made to similar specification to standard truss as they take no extra load

69 Truss Layout – Scotch Valley

70 Scotch Valley

71 Saddle or Valley Truss Used to form diminishing Minor Roof Edges form valley

72

73 End Truss Support


Download ppt "Roof Trusses. Definition Load Transferred Load Transferred Load not Transferred."

Similar presentations


Ads by Google