7 ACCURACY OF FABRICATION .................................................................... 2
7.1 GENERAL ...................................................................................................... 2
7.1.1 Scope 2
7.1.2 References 2
7.2 PERMITTED DEVIATIONS ........................................................................... 2
7.2.1 Permitted Deviations In Rolled Components After Fabrication 2
7.2.2 Permitted Deviations for Elements of Fabricated Members 3
7.2.3 Permitted Deviations In Plate Girder Sections 4
7.2.4 Permitted Deviations in Box Sections 7
7 ACCURACY OF FABRICATION
7.1 GENERAL
7.1.1 Scope
1 This Part deals with the accuracy of fabrication of structural steel sections.
7.1.2 References
1 The following standards are referred to in this Part:
BS 4 ............................Structural steel sections
BS 4848 ......................Hot rolled structural steel sections
BS 5950 ......................Structural use of steelwork in buildings
7.2 PERMITTED DEVIATIONS
7.2.1 Permitted Deviations In Rolled Components After Fabrication
1 Permitted deviations in rolled components after fabrication (including structural hollow sections) are given in Table 7.1
Table 7.1
Permitted Deviations in Rolled Components After Fabrication
Item
Component
Deviation
1
Cross Section after Fabrication
In accordance with the tolerances specified in BS 4 or BS 4848 as appropriate.
2
Squareness of Ends Not Prepared for Bearing
See also clause 4.4.3-1.
Plan or Elevation of End
3
Squareness of Ends Prepared for Bearing
Prepare ends with respect to the longitudinal axis of the member. See also Clauses 4.4.3-2 and 4.4.3-3.
Plan or Elevation
Table 7.1 (Continued)
Permitted Deviations in Rolled Components After Fabrication
Item
Component
Deviation
4
Straightness on Both Axes
. = L/1000 or 3mm
whichever is the greater
5
Length
Length after cutting, measured on the centre line of the section of angles.
6
Curved or Cambered
Deviation from intended curve or camber at mid-length of curved portion when measured with web horizontal.
Deviation = L/1000 or 6mm
whichever is greater
7.2.2 Permitted Deviations for Elements of Fabricated Members
1 Permitted deviations for elements of fabricated members are given in Table 7.2
Table 7.2
Permitted Deviations for Elements of Fabricated Members
Item
Component
Deviation
1
Position of Fittings
Fittings and components whose location is crucial to the force path in the structure, the deviation from the intended position shall not exceed ..
Table 7.2 (Continued)
Permitted Deviations for Elements of Fabricated Members
Item
Component
Deviation
2
Position of Holes
The deviation from the intended position of an isolated hole, also a group of holes, relative to each other shall not exceed .
3
Punched Holes
The distortion caused by a punched hole shall not exceed . (see clause 4.6.3)
. = D/10 or 1mm
whichever is the greater
4
Sheared or Cropped Edges of Plates or Angle
The deviation from a 90. edge shall not exceed .
5
Flatness
Where bearing is specified, the flatness shall be such that when measured against a straight edge not exceeding one metre long, which is laid against the full bearing surface in any direction, the gap does not exceed .
7.2.3 Permitted Deviations In Plate Girder Sections
1 Permitted deviations in plate girder sections are given in Table 7.3
Table 7.3
Permitted Deviations In Plate Girder Sections
Item
Component
Deviation
1
Depth
Depth on centre Line
2
Flange Width
Width of Bw or Bn
3
Squareness of Section
Out of Squareness of Flanges.
B Flange width
.
.=B/100 or 3mm whichever is greater
4
Web Eccentricity
Intended position of web from one edge of flange.
5
Flanges
Out of flatness
B Flange width
. = B/100 or 3mm
whichever is the greater
Table 7.3 (Continued)
Permitted Deviations In Plate Girder Sections
Item
Component
Deviation
6
Top Flange of Crane Girder
Out of flatness where the rail seats.
w = Rail width + 20 mm
7
Length
Length on centre line
8
Flange Straightness
Straightness of individual flanges
. = L/1000 or 3mm
whichever is the greater
9
Curved or Cambered
Deviation from intended curve or camber at mid-length of curved portion, when measured with the web horizontal.
Deviation = l/1000 or 6mm
whichever is the greater
10
Web Distortion
Distortion on web depth or gauge length.
gauge length = web depth
. = d/150 or 3mm
whichever is the greater
Table 7.3 (Continued)
Permitted Deviations In Plate Girder Sections
Item
Component
Deviation
11
Cross Section at Bearings
Squareness of flanges to web
12
Web Stiffeners
Straightness of stiffener out of plane after welding.
. = d/500 or 3mm
whichever is greater
13
Web Stiffeners
Straightness of stiffener in plane after welding.
. = d/250 or 3mm
whichever is greater
7.2.4 Permitted Deviations in Box Sections
1 Permitted deviations in box sections are given in table 7.4
Table 7.4
Permitted Deviations in Box Sections
Item
Component
Deviation
1
Plate Widths
Width of Bf or Bw
2
Squareness
Squareness at diaphragm positions
3
Plate Distortion
Distortion on width or gauge length.
gauge length = width, w
. = w/150 or 3mm
whichever is the greater
4
Web or Flange Straightness
Straightness of individual web or flanges.
. = L/1000 or 3mm
whichever is the greater
Table 7.4 (Continued)
Permitted Deviations in Box Sections
Item
Component
Deviation
5
Web Stiffners
Straightness in plane with plate after welding.
. = d/500 or 3mm
whichever is the greater
6
Web Stiffners
Straightness out of plane to plate after welding.
. = d/250 or 3mm
whichever is the greater
7
Length
Length on centre line.
8
Curved or Cambered
Deviation from intended curve or camber at mid-length of curved portion when measured with the uncambered side horizontal.
Deviation = L/1000 or 6mm
whichever is the greater
END OF PART