NCC 2016 Volume Two
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Part 3.4.4 Structural Steel Members

Part 3.4.4 Structural Steel Members

Appropriate Performance Requirements

Appropriate Performance Requirements

Where an alternative structural steel member system is proposed as a Performance Solution to that described in Part 3.4.4, that proposal must comply with—

  1. P2.1.1; and
  2. the relevant Performance Requirements determined in accordance with 1.0.7.

Explanation of Terms

3.4.4

The following terms are used in this Part:

Figure 3.4.4.0

EFFECTIVE MEMBER SPACING FOR STRUCTURAL STEEL BEARERS AND STRUTTING BEAMS

Diagram a. Single spanning rafter or joist
v2_Fig3440a_2006.svg
Design member Member 1 Member 2
Effective member spacing 0.5 x Span 1 0.5 x (Span 1 + Span 2)
Diagram b. Continuous spanning rafter or joist
v2_Fig3440b_2006.svg
Design member Member 1 Member 2 Member 3
Effective member spacing 0.4 x Span 1 0.6 x (Span 1 + Span 2) 0.5 x (Span 2) + Span 3

Steel member abbreviations are as follows:

TFB means a tapered flange beam.
UB means a universal beam.
RHS means a rectangular hollow section.
PFC means a parallel flange channel.
TFC means a tapered flange channel.
EA means an equal angle.
UA means an unequal angle.
SHS means a square hollow section.
CHS means a circular hollow section.

Acceptable construction manuals

3.4.4.0

P2.1.1 is satisfied for structural steel sections if they are designed and constructed in accordance with one of the following:

(a)

Steel structures: AS 4100.

(b)

Cold-formed steel structures: AS/NZS 4600.

Explanatory information

Explanatory information:

Design requirements for other materials used in combination with structural steel members are described in Part 3.4.2, 3.4.3 or Part 3.11 — Structural design manuals.

Acceptable construction practice

3.4.4.1 Application

(a)

Compliance with this acceptable construction practice satisfies in respect to structural stability, provided—

(i)

the building is located in an area with a design wind speed of not more than N3; and

Explanatory information

Explanatory information:
  1. Information on design wind speeds for particular areas may be available from the appropriate authority.
  2. A map indicating cyclonic regions of Australia is contained in Part 3.10.1.
(ii)

the first dimension of steel sections is installed vertically; and

(iii)

all loads are uniformly distributed (unless otherwise noted or allowed for); and

(iv)

the building is one for which Appendix A of AS 1170.4 contains no specific earthquake design requirements; and

Explanatory information

Explanatory information:

There are certain limitations on the application to domestic structures such as Class 1a and 1b buildings in Appendix A of AS 1170.4. These limitations include building height, roof slope, etc. For additional information refer to Appendix A of AS 1170.4.

(v)

the structural steel member is not subject to snow loads.

(b)

Compliance with 3.4.4.4 satisfies in respect to corrosion protection requirements.

3.4.4.2 Structural steel members

(a)

Structural steel members may be used as follows:

(i)

Bearers supporting a timber floor or non-loadbearing stud wall — in accordance with Figure 3.4.4.1.

(ii)

Strutting beams supporting roof and ceiling loads — in accordance with Figure 3.4.4.2.

(iii)

Lintels supporting roof, ceiling, frame and timber floor — in accordance with Figure 3.4.4.3.

(iv)

Columns — in accordance with 3.4.4.3.

(b)

Structural steel members described in this Part must be protected against corrosion in accordance with 3.4.4.4.

(c)

Joists, bearers and lintels must be restrained from lateral movement or twisting along their length by fixing rafters or joists to the top flange of the member so that it prevents that member from moving laterally.

(d)

End supports for joists, bearers and lintels must transfer loads to the footings and have a bearing distance as follows:

(i)

For single spans, the bearing distance must not be less than the width of the member.

(ii)

For continuous spans, internal bearing must be not less than two times the width of the member.

Figure 3.4.4.1

BEARER SUPPORTING A TIMBER FLOOR AND NON-LOADBEARING STUD WALL

v2_Fig3441_2010.svg
Table a. — Acceptable bearer spans
Steel section SINGLE SPAN CONTINUOUS SPAN
Effective bearer spacing (m) Effective bearer spacing (m)
1.8 2.4 3.0 3.6 4.2 1.8 2.4 3.0 3.6 4.2
MAXIMUM SPAN OF BEARER (M) MAXIMUM SPAN OF BEARER (M)
125TFB 4.1 3.8 3.6 3.4 3.2 4.7 4.3 3.8 3.5 3.2
180UB16.1 5.1 4.7 4.5 4.3 4.1 5.9 5.5 5.2 5.0 4.7
200UB18.2 5.6 5.2 5.0 4.7 4.6 6.5 6.0 5.7 5.5 5.3
250UB25.7 6.8 6.4 6.0 5.8 5.6 7.9 7.4 7.0 6.7 6.4
250x150x9.0 RHS 7.7 7.1 6.7 6.4 6.2 8.8 8.2 7.8 7.4 7.1
250x150x5.0 RHS 6.8 6.3 5.9 5.7 5.5 7.8 7.2 6.8 6.5 6.3
310UB32.0 7.9 7.3 7.0 6.7 6.4 9.1 8.5 8.1 7.7 7.4
125x75x2.0 RHS 3.1 2.8 2.6 2.5 2.4 4.0 3.7 3.5 3.3 3.1
125x75x3.0 RHS 3.5 3.2 3.0 2.8 2.7 4.4 4.1 3.9 3.7 3.5
150x50x2.0 RHS 3.4 3.1 2.8 2.7 2.5 4.2 3.9 3.7 3.5 3.4
150x50x3.0 RHS 3.7 3.4 3.2 3.0 2.9 4.6 4.3 4.1 3.9 3.7
100TFC 3.2 2.9 2.7 2.6 2.4 3.7 3.2 2.8 2.6 2.4
150PFC 4.8 4.5 4.2 4.0 3.9 5.5 5.1 4.9 4.7 4.5
180PFC 5.4 5.1 4.8 4.6 4.4 6.3 5.9 5.6 5.3 5.1
200PFC 5.9 5.5 5.2 5.0 4.8 6.8 6.3 6.0 5.7 5.5
250PFC 7.2 6.7 6.4 6.1 5.9 8.4 7.8 7.4 7.1 6.8
300PFC 8.1 7.6 7.2 6.9 6.6 9.4 8.8 8.3 8.0 7.7
Notes:
  1. Steel is base grade.
  2. Load must be evenly distributed along the member.
  3. For continuous floor bearers, the variation in span length should not be more than 10%.
  4. See 3.4.2.3 for provisions that apply to suspended floors in single-storey and ground floor construction of suspended steel floor frames.
  5. Effective bearer spacing is a measure of the width of the load area being supported by the member (see Figure 3.4.4.0).

Figure 3.4.4.2

STRUTTING BEAM SUPPORTING A ROOF AND CEILING

Strutting beam application
v2_Fig3442_2005.svg
Table a. — Acceptable strutting beam spans
Steel section STEEL SHEET ROOF TILED ROOF
Strutting beam spacing (m) Strutting beam spacing (m)
1.8 2.4 3.0 3.6 4.2 1.8 2.4 3.0 3.6 4.2
MAXIMUM SPAN OF STRUTTING BEAM (M) MAXIMUM SPAN OF STRUTTING BEAM (M)
125TFB 5.7 5.4 5.1 4.9 4.6 4.9 4.6 4.4 4.2 4.1
150UB14.0 6.4 6.0 5.7 5.4 5.1 5.5 5.2 4.9 4.7 4.5
200UB18.2 7.9 7.4 7.1 6.8 6.5 6.9 6.4 6.1 5.8 5.6
250UB31.4 10.0 9.4 9.0 8.7 8.4 8.8 8.2 7.8 7.5 7.2
310UB46.2 11.9 11.3 10.8 10.5 10.1 10.6 10.0 9.5 9.1 8.8
100TFC 4.6 4.4 4.2 3.9 3.7 4.0 3.7 3.6 3.4 3.2
150PFC 6.7 6.3 6.0 5.8 5.6 5.8 5.5 5.2 5.0 4.8
200PFC 8.2 7.7 7.4 7.1 6.8 7.2 6.7 6.4 6.1 5.9
250PFC 10.0 9.4 9.0 8.7 8.4 8.8 8.2 7.8 7.5 7.3
300PFC 11.1 10.5 10.1 9.7 9.4 9.8 9.3 8.8 8.4 8.2
Notes:
  1. If point load applied, then it should be located within the middle third of the strutting beam span.
  2. Top and bottom flanges of strutting beam must be laterally restrained at the loading point.
  3. Strutting beam must be tied down at the support points, in the case of steel sheet roofs.
  4. Steel is base grade.

Figure 3.4.4.3

LINTELS SUPPORTING ROOF, FRAMES AND TIMBER FLOORS

Lintels supporting roof and floors
v2_Fig3443_2005.svg
Table a. — Acceptable spans for lintels
Steel section STEEL SHEET ROOF TILED ROOF
Effective load width (m) Effective load width (m)
1.8 2.4 3.0 3.6 4.2 1.8 2.4 3.0 3.6 4.2
MAXIMUM SPAN OF LINTEL (M) MAXIMUM SPAN OF LINTEL (M)
125TFB 3.7 3.4 3.2 3.0 2.8 3.6 3.3 3.0 2.9 2.7
150UB14.0 4.1 3.9 3.7 3.5 3.3 4.0 3.7 3.5 3.3 3.2
200UB25.4 5.6 5.3 5.0 4.8 4.7 5.4 5.1 4.8 4.6 4.5
250UB31.4 6.6 6.2 5.9 5.7 5.5 6.3 6.0 5.7 5.4 5.2
100TFC 2.8 2.6 2.4 2.3 2.1 2.7 2.5 2.3 2.1 2.0
150PFC 4.4 4.1 3.9 3.7 3.6 4.2 3.9 3.7 3.6 3.4
200PFC 5.4 5.0 4.8 4.6 4.4 5.1 4.8 4.6 4.4 4.2
250PFC 6.6 6.2 5.9 5.7 5.5 6.3 6.0 5.7 5.4 5.3
75x75x5EA 1.3 1.2 1.1 – – 1.3 1.1 – – –
90x90x6EA 1.9 1.6 1.5 1.3 1.2 1.7 1.5 1.4 1.3 1.2
100x100x6EA 2.0 1.8 1.6 1.5 1.4 1.9 1.7 1.5 1.4 1.3
125x75x6UA 2.3 2.0 1.8 1.7 1.5 2.2 1.9 1.7 1.6 1.4
150x100x10UA 3.9 3.6 3.2 2.9 2.7 3.7 3.3 3.0 2.8 2.6
Notes:
  1. Top flange of lintel must be laterally restrained at the loading points.
  2. Load must be evenly distributed along the member (e.g. joists).
  3. Angle lintels — first dimension corresponds to vertical leg (e.g. 100x75x6UA, 100 mm leg is vertical).
  4. For lintels supporting masonry walls, see Part 3.3.3.

3.4.4.3 Columns

Columns may support the area provided for in Table 3.4.4.1 provided—

(a)

the effective height of the column is determined in accordance with Figure 3.4.4.4; and

(b)

the floor area to be supported is determined in accordance with Figure 3.4.4.5; and

(c)

the load eccentricity between the centre of the column and the applied vertical loading complies with Figure 3.4.4.6.

Figure 3.4.4.4

DETERMINING EFFECTIVE COLUMN HEIGHT

Diagram a. Column height (H)
v2_Fig3444_2005.svg
Table a. Column height factor (F1)
BASE DETAIL BRACING SYSTEM
Fully Braced (1) Construction Unbraced Construction (cantilever columns) (2)
Cast into footing 1.00 2.60
Fixed by bolts to footing or slab 1.20 must not be used
Fixed by intermediate floor or bracing in both directions 1.20 2.60
Notes:
  1. For the purposes of this Figure, to determine the column effective height, the actual column height (H) in Diagram a. must be multiplied by a column height factor (F1) in Table a.
  2. H = Distance measured from the top of footing to underside of supported beam or bearer, or between intermediate lateral bracing points.
  3. The flooring system must be fully braced to footing level by—
    1. a combination of column bracing sets, and timber or masonry bracing walls; or
    2. the provision of cantilever steel columns only (i.e. no column bracing sets, timber or masonry bracing walls).

Figure 3.4.4.5

DETERMINING FLOOR AREA SUPPORTED

Diagram a. AREA SUPPORTED BY COLUMNS (Plan view) Table a. AREA SUPPORTED BY COLUMNS
v2_Fig3445_2005.svg
 COLUMN TOTAL AREA SUPPORTED
C1 0.375L1 x 0.375LA
C2 0.625(L1 + L2) x 0.375LA
C3 0.375L1 x 0.625(LA + LB)
C4 0.625(L1 + L2) x 0.625(LA + LB)
C5 0.375L1 x (L cant + 0.5LC)
C6 0.625(L1 + L2) x (L cant + 0.5LC)
Note: The total area supported depends on the position of the column in the structure as shown in Diagram a. To calculate the correct area supported by a column, match the column’s position with those shown in Diagram a. which shows a plan view of a floor and then calculate the total area supported from Table a.

Figure 3.4.4.6

ACCEPTABLE LOAD ECCENTRICITY FOR COLUMNS

v2_Fig3446_2005.svg

Table 3.4.4.1 COLUMNS

COLUMNS – SUPPORTING TIMBER FLOOR ONLY
COLUMN EFFECTIVE HEIGHT (mm) FLOOR AREA SUPPORTED (m2)
5 10 15 20 25
CHS C250 600 60.3 x 3.6 88.9 x 4.0 101.6 x 5.0 114.3 x 5.4 139.7 x 5.0
1200 60.3 x 4.5 88.9 x 4.0 101.6 x 5.0 114.3 x 5.4 139.7 x 5.0
1800 60.3 x 4.5 88.9 x 4.0 101.6 x 5.0 114.3 x 5.4 139.7 x 5.0
2400 60.3 x 4.5 88.9 x 4.0 101.6 x 5.0 114.3 x 5.4 139.7 x 5.0
3600 76.1 x 3.6 101.6 x 4.0 114.3 x 4.5 139.7 x 5.0 139.7 x 5.0
CHS C350 600 60.3 x 2.9 88.9 x 2.6 101.6 x 3.2 114.3 x 3.6 139.7 x 3.5
1200 60.3 x 2.9 88.9 x 2.6 101.6 x 3.2 114.3 x 3.6 139.7 x 3.5
1800 60.3 x 2.9 101.6 x 2.6 114.3 x 3.2 114.3 x 3.6 139.7 x 3.5
2400 76.1 x 2.3 101.6 x 2.6 114.3 x 3.2 139.7 x 3.0 139.7 x 3.5
3600 88.9 x 2.6 101.6 x 2.6 114.3 x 3.2 139.7 x 3.0 165.1 x 3.0
SHS C350 600 50 x 50 x 2.5 75 x 75 x 2.5 75 x 75 x 4.0 100 x 100 x 4.0 100 x 100 x 4.0
1200 65 x 65 x 2.0 75 x 75 x 2.5 75 x 75 x 4.0 100 x 100 x 4.0 100 x 100 x 4.0
1800 65 x 65 x 2.0 75 x 75 x 3.0 100 x 100 x 3.0 100 x 100 x 4.0 100 x 100 x 4.0
2400 65 x 65 x 2.0 75 x 75 x 3.0 100 x 100 x 3.0 100 x 100 x 4.0 100 x 100 x 5.0
3600 65 x 65 x 2.5 75 x 75 x 4.0 100 x 100 x 3.0 100 x 100 x 4.0 100 x 100 x 5.0
SHS C450 600 50 x 50 x 2.0 65 x 65 x 2.5 75 x 75 x 3.0 100 x 100 x 2.8 100 x 100 x 3.3
1200 50 x 50 x 2.0 65 x 65 x 2.5 75 x 75 x 3.0 100 x 100 x 3.0 100 x 100 x 3.3
1800 50 x 50 x 2.3 75 x 75 x 2.3 75 x 75 x 3.3 100 x 100 x 3.0 100 x 100 x 3.8
2400 65 x 65 x 2.0 75 x 75 x 2.5 75 x 75 x 3.5 100 x 100 x 3.0 100 x 100 x 3.8
3600 65 x 65 x 2.3 100 x 100 x 2.0 100 x 100 x 2.8 100 x 100 x 3.8 100 x 100 x 4.0
COLUMNS — SUPPORTING TILE ROOF ONLY
CHS C250 600 60.3 x 3.6 60.3 x 3.6 76.1 x 3.6 76.1 x 4.5 88.9 x 4.0
1200 60.3 x 3.6 60.3 x 3.6 76.1 x 3.6 76.1 x 4.5 101.6 x 4.0
1800 60.3 x 3.6 60.3 x 3.6 76.1 x 3.6 76.1 x 4.5 101.6 x 4.0
2400 60.3 x 3.6 60.3 x 4.5 76.1 x 3.6 88.9 x 4.0 101.6 x 4.0
3600 60.3 x 3.6 76.1 x 3.6 76.1 x 4.5 88.9 x 4.0 101.6 x 4.0
CHS C350 600 60.3 x 2.3 60.3 x 2.3 76.1 x 2.3 88.9 x 2.6 101.6 x 2.6
1200 60.3 x 2.3 60.3 x 2.9 76.1 x 2.3 88.9 x 2.6 101.6 x 2.6
1800 60.3 x 2.3 60.3 x 2.9 88.9 x 2.6 88.9 x 2.6 101.6 x 2.6
2400 60.3 x 2.3 76.1 x 2.3 88.9 x 2.6 88.9 x 2.6 101.6 x 2.6
3600 60.3 x 2.3 76.1 x 2.3 88.9 x 2.6 101 x 2.6 101.6 x 3.2
SHS C350 600 50 x 50 x 2.0 50 x 50 x 2.5 65 x 65 x 2.5 75 x 75 x 2.5 75 x 75 x 3.0
1200 50 x 50 x 2.0 50 x 50 x 2.5 65 x 65 x 2.5 75 x 75x 2.5 75 x 75 x 3.0
1800 50 x 50 x 2.0 65 x 65 x 2.0 65 x 65 x 2.5 75 x 75 x 2.5 75 x 75 x 3.0
2400 50 x 50 x 2.0 65 x 65 x 2.0 65 x 65 x 2.5 75 x 75 x 2.5 75 x 75 x 4.0
3600 50 x 50 x 2.5 65 x 65 x 2.5 75 x 75 x 2.5 75 x 75 x 3.0 75 x 75 x 4.0
SHS C450 600 50 x 50 x 1.6 50 x 50 x 2.0 65 x 65 x 2.0 65 x 65 x 2.3 65 x 65 x 2.8
1200 50 x 50 x 1.6 50 x 50 x 2.0 65 x 65 x 2.0 65 x 65 x 2.3 65 x 65 x 2.8
1800 50 x 50 x 1.6 65 x 65 x 1.6 65 x 65 x 2.0 65 x 65 x 2.5 75 x 75 x 2.5
2400 50 x 50 x 1.6 50 x 50 x 2.5 65 x 65 x 2.3 75 x 75 x 2.3 75 x 75 x 2.8
3600 50 x 50 x 2.0 65 x 65 x 2.0 75 x 75 x 2.3 100 x 100 x 2.0 100 x 100 x 2.3
Note: Tabulated values are the column sections to be used.

3.4.4.4 Corrosion protection

Structural steel members that are not built into a masonry wall must be protected against corrosion in accordance with Table 3.4.4.2.

Table 3.4.4.2 PROTECTIVE COATINGS FOR STEELWORK

ENVIRONMENT LOCATION MINIMUM PROTECTIVE COATING
General structural steel members

MODERATE

More than 1 km from breaking surf or more than 100 m from salt water not subject to breaking surf or non-heavy industrial areas

 INTERNAL No protection required in a permanently dry locationNote 6
EXTERNAL Option 1. 2 coats alkyd primer
Option 2. 2 coats alkyd gloss
Option 3. Hot dip galvanise 300 g/m2 min
Option 4. Hot dip galvanise 100 g/m2 min plus—
(a) 1 coat solvent based vinyl primer; or
(b) 1 coat vinyl gloss or alkyd.

SEVERE

Within 1 km from breaking surf or within 100 m of salt water not subject to breaking surf or heavy industrial areas

 INTERNAL Option 1. 2 coats alkyd primer
Option 2. 2 coats alkyd gloss
EXTERNAL Option 1. Inorganic zinc primer plus 2 coats vinyl gloss finishing coats
Option 2. Hot dip galvanise 300 g/m2
Option 3. Hot dip galvanise 100 g/m2 min plus—
(a) 2 coats solvent based vinyl primer; or
(b) 2 coats vinyl gloss or alkyd.

Notes:

  1. Heavy industrial areas means industrial environments around major industrial complexes. There are only a few such regions in Australia, examples of which occur around Port Pirie and Newcastle.
  2. The outer leaf and cavity of an external masonry wall of a building, including walls under open carports are considered to be external environments. A part of an internal leaf of an external masonry wall which is located in the roof space is considered to be in an internal environment.
  3. Where a paint finish is applied the surface of the steel work must be hand or power tool cleaned to remove any rust immediately prior to painting.
  4. All zinc coatings (including inorganic zinc) require a barrier coat to stop conventional domestic enamels from peeling.
  5. Refer to the paint manufacturer where decorative finishes are required on top of the minimum coating specified in the table for protection of the steel against corrosion.
  6. Internal locations subject to moisture, such as in close proximity to kitchen or bathroom exhaust fans are not considered to be in a permanently dry location and protection as specified for external locations is required.
  7. For applications outside the scope of this table, seek specialist advice.