NCC 2019 Volume Two
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Part 3.0 Structural provisions

Part 3.0 Structural provisions

Appropriate Performance Requirements

Appropriate Performance Requirements

Where it is proposed to use an alternative structural design manual as a Performance Solution to that described in Part 3.0, that proposal must comply with—

  1. Performance RequirementP2.1.1; and
  2. the relevant Performance Requirements determined in accordance with A2.2(3) and A2.4(3) as applicable.

3.0.1 Application

Compliance with this Acceptable Construction Practice satisfies Performance Requirement P2.1.1 provided the Class 1 or Class 10 building is constructed in accordance with—

(a)

3.0.2 to 3.0.5; or

(b)

the relevant provisions of other Parts of Section 3 of the Housing Provisions relating to structural elements; or

(c)

any combination thereof.

3.0.2 Resistance to actions

The resistance of a building or structure must be greater than the most critical action effect resulting from different combinations of actions, where—

(a)

the most critical action effect on a building or structure must be determined in accordance with 3.0.3 and the general design procedures contained in AS/NZS 1170.0; and

(b)

the resistance of a building or structure is determined in accordance with 3.0.4.

Explanatory information:

Explanatory information:

A building or structure must be designed to resist the most critical effect resulting from different combinations of actions, taking into consideration—

  1. the probability of simultaneous occurrence of two or more actions; and
  2. the levels of reliability of the structure when subject to combined actions; and
  3. the characteristics of the action.

Determining the levels of reliability of the structure when subject to combined actions should be consistent with the levels of reliability implicit in the design events for natural phenomenon.

When designing for the maximum combined actions, a principle frequently adopted is that the maximum is likely to occur when at least one of the actions is at its maximum value.

3.0.3 Determination of individual actions

The magnitude of individual actions must be determined in accordance with the following:

(a)

Permanent actions:

(i)

the design or known dimensions of the building or structure; and

(ii)

the unit weight of the construction; and

(iii)

AS/NZS 1170.1.

(b)

Imposed actions:

(i)

the known loads that will be imposed during the occupation or use of the building or structure; and

(iii)

AS/NZS 1170.1.

Explanatory information:

Explanatory information:

Permanent actions include the dead loads of the building or structure. These include the load imposed by the building's components inclusive of the forces imposed by the floors, walls, roofs, suspended ceilings, etc.

Imposed actions include live loads on the building or structure. These include the load arising from construction activity and the intended use or function of the building or structure.

(c)

Wind, snow and earthquake actions:

(i)

the applicable annual probability of design event for safety, determined by—

(A)

assigning the building or structure an Importance Level in accordance with Table 3.0.3a; and

(B)

determining the corresponding annual probability of exceedance for safety in accordance with Table 3.0.3b; and

(ii)

for wind actions, AS/NZS 1170.2 or AS 4055; and

(iii)

for snow and ice actions, AS/NZS 1170.3; and

(iv)

for earthquake actions, AS 1170.4.

Explanatory information:

Explanatory information:

There are certain limitations on the application to domestic structures such as Class 1a and Class 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.

State and Territory Variations

State and Territory Variations

3.0.3(c)(v) is added in the Northern Territory.

(v) Masonry veneer — Masonry veneer construction must be designed so that the structural framing to which the masonry veneer is tied will ensure the stability of the masonry veneer.

(d)

Actions not covered in (a), (b) and (c) above:

(i)

the nature of the action; and

(ii)

the nature of the building or structure; and

(iii)

the Importance Level of the building or structure determined in accordance with Table 3.0.3a; and

(iv)

AS/NZS 1170.1.

(e)

For the purposes of (d) the actions include but are not limited to—

(i)

liquid pressure action; and

(ii)

ground water action; and

(iii)

rainwater action (including ponding action); and

(iv)

earth pressure action; and

(v)

differential movement; and

(vi)

time dependent effects (including creep and shrinkage); and

(vii)

thermal effects; and

(viii)

ground movement caused by—

(A)

swelling, shrinkage or freezing of the subsoil; and

(B)

landslip or subsidence; and

(C)

siteworks associated with the building or structure; and

Table 3.0.3a Importance Levels of buildings and structures

Importance Level

Building types

1

Buildings or structures presenting a low degree of hazard to life and other property in the case of failure.

2

Buildings or structures not included in Importance Level 1.

Explanatory information:

Explanatory information:

Table 3.0.3a provides a generic description of building types to which Importance Levels have been assigned. The "Importance Level" concept is applicable to building structural safety only. More specific examples are provided in the following Table. The examples are indicative and not exhaustive.

Importance Level examples

Importance Level

Examples of building types

1

Isolated minor Class 10a buildings and Class 10b structures.

2

Class 1 buildings.

Class 10a buildings and Class 10b structures associated with Class 1 buildings.

Note: Importance Levels must be assigned on a case by case basis and relate to the hazards to human life and other property in the event of the structure's failure. For example—

  1. Importance Level 1 is for minor isolated structures that rarely contain people, are not required as part of normal infrastructure and present a low risk to life and other property.
  2. Importance Level 2 includes domestic housing and structures intended to contain reasonable numbers of people under normal operations.
Table 3.0.3b Design events for safety—annual probability of exceedance

Importance level

Non-cyclonic wind

Cyclonic wind

Snow

Earthquake

1

1:100

1:200

1:100

1:250

2

1:500

1:500

1:150

1:500
Figure 3.0.1 Wind regions
v2_Fig301_2019.svg

Explanatory information:

Explanatory information:

Construction in cyclonic areas

The intent of building construction in cyclonic areas (see Figure 3.0.1) is to ensure the structure has sufficient strength to transfer wind forces to the ground with an adequate safety margin to prevent collapse of the building and the building being lifted, or slid off its foundations.

To resist these forces it is necessary to have—

  1. an anchorage system, where the roof is connected by the walls to the footings by a chain of connections; and
  2. a bracing system to prevent horizontal collapse due to wind forces; and
  3. continuity of the system where each structural element is interlocked to its adjoining structural element throughout the building.

Anchorage

Anchorage of the system is achieved by using a variety of connectors. Each connector must be capable of carrying the uplift force, because the ability of the building to resist the wind forces is directly related to its weakest link.

Acceptable construction manuals to achieve these requirements are described in this Part.

3.0.4 Determination of structural resistance of materials and forms of construction

The following requirements, or any combination of them, must be used to determine the structural resistance of materials and forms of construction as appropriate:

(a)

Earthworks: Part 3.1.

(b)

Earth retaining structures: Part 3.1.

(c)

Termite risk management: Part 3.1.

(d)

Concrete construction (including slabs and footings, piled footings and reinforced and prestressed concrete structures): Part 3.2 or AS 3600 as applicable.

(e)

Post-installed and cast-in fastenings in concrete: AS 5216.

(f)

Masonry (including masonry veneer, unreinforced masonry and reinforced masonry): Part 3.3.

(g)

Steel construction (including steel framing and structural steel members): Part 3.4.

(h)

Timber construction (including design of timber structures, timber framing and design of nail-plated timber roof trusses): Part 3.4.

(i)

Composite steel and concrete: AS/NZS 2327.

(j)

Aluminium construction:

(i)

AS/NZS 1664.1.

(ii)

AS/NZS 1664.2.

(k)

Roof construction (including plastic sheeting, roofing tiles, metal roofing and terracotta, fibre-cement and timber slates and shingles): Part 3.5.

(l)

Wall cladding: Part 3.5.

(m)

Glazed assemblies: Part 3.6.

(n)

Barriers and handrails (including stairway and ramp construction):

(i)

Part 3.9; and

(ii)

AS/NZS 1170.1 for the determination of loading forces on a barrier.

(o)

Attachment of decks and balconies to external walls of buildings: Part 3.10.

(p)

Garage doors and other large access doors in openings not more than 3 m in height in external walls of buildings determined as being located in wind region C or D in accordance with Figure 3.0.1: AS/NZS 4505.

(q)

For high wind areas: requirements listed in 3.0.4 as appropriate or the Northern Territory Deemed to Comply Standards Manual.

Explanatory information:

Explanatory information:

The weight of roof or ceiling insulation, particularly if additional ceiling insulation is used for compliance with the energy efficiency provisions, needs to be considered in the selection of plasterboard, plasterboard fixings and building framing.

3.0.5 Structural software

(a)

Structural software used in computer aided design of a building or structure, that uses design criteria based on the Deemed-to-Satisfy Provisions of the Housing Provisions, including its referenced documents, for the design of steel or timber trussed roof and floor systems and framed building systems, must comply with the ABCB Protocol for Structural Software.

(b)

The requirements of (a) only apply to structural software used to design steel or timber trussed roof and floor systems and framed building systems for buildings within the following geometrical limits:

(i)

The distance from ground level to the underside of eaves must not exceed 6 m.

(ii)

The distance from ground level to the highest point of the roof, neglecting chimneys, must not exceed 8.5 m.

(iii)

The building width including roofed verandahs, excluding eaves, must not exceed 16 m.

(iv)

The building length must not exceed five times the building width.

(v)

The roof pitch must not exceed 35 degrees.

(c)

The requirements of (a) do not apply to design software for individual frame members such as electronic tables similar to those provided in—

(i)

AS 1684 Parts 2, 3 and 4; or

(ii)

NASH Standard Residential and Low-Rise Steel Framing, Part 2.

Explanatory information:

Explanatory information:

3.0.5 does not apply where a software package simply eliminates manual calculations and the process of the package requires identical methodology as that undertaken manually, e.g. AS 1684 span tables and bracing calculations.