NCC 2019 Volume Two
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Part 2.1 Structure

Part 2.1 Structure

Explanatory information:

Explanatory information:

Objective

O2.1

The Objective is to—

  1. safeguard people from injury caused by structural failure; and
  2. safeguard people from loss of amenity caused by structural behaviour; and
  3. protect other property from physical damage caused by structural failure; and
  4. safeguard people from injury that may be caused by failure of, or impact with, glazing.

Functional statements

F2.1

  1. A building or structure is to withstand the combination of loads and other actions to which it may be reasonably subjected.
  2. Glazing is to be installed in a building to avoid undue risk of injury to people.

Performance Requirements

P2.1.1 Structural stability and resistance

(a)

A building or structure, during construction and use, with appropriate degrees of reliability, must—

(i)

perform adequately under all reasonably expected design actions; and

(ii)

withstand extreme or frequently repeated design actions; and

(iii)

be designed to sustain local damage, with the structural system as a whole remaining stable and not being damaged to an extent disproportionate to the original local damage; and

(iv)

avoid causing damage to other properties,

by resisting the actions to which it may reasonably be expected to be subjected.

(b)

The actions to be considered to satisfy (a) include but are not limited to—

(i)

permanent actions (dead loads); and

(ii)

imposed actions (live loads arising from occupancy and use); and

(iii)

wind action; and

(iv)

earthquake action; and

(v)

snow action; and

(vi)

liquid pressure action; and

(vii)

ground water action; and

(viii)

rainwater action (including ponding action); and

(ix)

earth pressure action; and

(x)

differential movement; and

(xi)

time dependent effects (including creep and shrinkage); and

(xii)

thermal effects; and

(xiii)

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

(xv)

termite actions.

(c)

The structural resistance of materials and forms of construction must be determined using five percentile characteristic material properties with appropriate allowance for—

(i)

known construction activities; and

(ii)

type of material; and

(iii)

characteristics of the site; and

(iv)

the degree of accuracy inherent in the methods used to assess the structural behaviour; and

(v)

action effects arising from the differential settlement of foundations, and from restrained dimensional changes due to temperature, moisture, shrinkage, creep and similar effects.

(d)

Glass installations that are at risk of being subjected to human impact must have glazing that—

(i)

if broken on impact, will break in a way that is not likely to cause injury to people; and

(ii)

resists a reasonably foreseeable human impact without breaking; and

(iii)

is protected or marked in a way that will reduce the likelihood of human impact.

P2.1.2 Buildings in flood areas

(a)

A building in a flood hazard area must be designed and constructed, to the degree necessary, to resist flotation, collapse or significant permanent movement resulting from the action of hydrostatic, hydrodynamic, erosion and scour, wind and other actions during the defined flood event.

(b)

The actions and requirements to be considered to satisfy (a) include but are not limited to—

(i)

flood actions; and

(ii)

elevation requirements; and

(iii)

foundation and footing requirements; and

(iv)

requirements for enclosures below the flood hazard level; and

(v)

requirements for structural connections; and

(vi)

material requirements; and

(vii)

requirements for utilities; and

(viii)

requirements for occupant egress.

Limitation:

Limitation:

P2.1.2 only applies to a Class 1 building.

State and Territory Variations

State and Territory Variations

P2.1.2 does not apply in Queensland.

Note: Building work in designated flood hazard areas is regulated by the Building Act 1975 and Development Code 3.5 - Construction of buildings in flood hazard areas.

In Queensland after P2.1.2 insert QLD P2.1.3 as follows:

QLD P2.1.3

  1. The risk of primary building elements in a Class 1 or 10 building being damaged by subterranean termites must be adequately minimised by the use of a suitable termite management measure that—
    1. if it serves a non-temporary Class 1 building, has a design life of at least 50 years; or
    2. if it serves a building not specified in (i), has a design life of at least 50 years or the specified design life of the building, whichever is the lesser; or
    3. is easily and readily accessible for replenishment or replacement and is capable of being replenished or replaced.
  2. A termite management measure required by (a), to the degree necessary, must—
    1. be accessible to enable the installation, maintenance and inspection of the termite management measure to be carried out; and
    2. incorporate suitable measures to adequately minimise the risk of the termite management measure inadvertently being damaged, bridged or breached.

Explanatory information:

Explanatory information:

QLD P2.1.3(a) requires a termite management measure in Queensland to have a design life of at least 50 years unless it is easily and readily accessible for replenishment or replacement and is capable of being replenished or replaced. In recognition that some buildings other than non-temporary Class 1 buildings may be designed to last less than 50 years, the option of the termite management measure having a design life at least equal to that specified for the building is given. If this option is used, the design life of the building should be agreed upon by all relevant stakeholders at the design stage and should form part of the documentation kept by the appropriate authority. It should not be assumed that the design life of 50 years in QLD P2.1.3(a)(i) and (ii) applies to any other provisions of the BCA, unless stated.

An example of a termite management measure that may satisfy QLD P2.1.3(a)(iii) is a chemical reticulation system beneath a concrete floor slab laid directly on the ground, provided that the system is easily and readily accessible for replenishment and is capable of being replenished.

An example of a termite management measure that may not satisfy QLD P2.1.3(a) for a non-temporary Class 1 building is a hand-sprayed chemical beneath a concrete floor slab laid directly on the ground if the chemical does not have a design life of at least 50 years. The concrete floor slab being laid directly on the ground would prevent the area beneath the slab from being easily and readily accessible for replenishment or replacement of the termite management measure.

An example of a termite management measure being inadvertently bridged or breached is when a person places a garden or mulch over the top of or above the level of a termite management measure enabling termites to bypass the measure.

P2.1.2 does not apply in South Australia.

Verification Methods

V2.1.1 Structural reliability

(a)

This Verification Method is only applicable to components with a resistance coefficient of variation of at least 10% and not more than 40%. For components with a calculated value less than 10%, then a minimum value of 10% should be used.

(b)

Compliance with P2.1.1(a), (b) and (c) is verified for the design of a structural component for strength when—

(i)

the capacity reduction factor ϕ satisfies—

ϕ ≤= Average (ϕG, ϕQ, ϕW,…),

where—

ϕG, ϕQ, ϕW,… are capacity reduction factors for all relevant actions and must contain at least permanent (G), imposed (Q) and wind (W) actions; and

(ii)

the capacity reduction factors ϕ G, ϕ Q, ϕ W,… are calculated for target reliability indices for permanent action βTG, for imposed action βTQ, for wind action βTW, … in accordance with the Equation 1—

Equation 1
v2_Fig21Eq1a_2019.svg

where—

v2_Fig21Eq1b_2019.svg
v2_Fig21Eq1c_2019.svg

where—

v2_Fig21Eq1d_2019.svg

= ratio of mean resistance to nominal; and
v2_Fig21Eq1e_2019.svg

= ratio of mean action to nominal; and

CS = correction factor for action; and

CR = correction factor for resistance; and

VS = coefficient of variation of the appropriate action as given in Table V2.1.1a; and

VR = coefficient of variation of the resistance; and

γ = appropriate load factor for the action as given in AS/NZS 1170.0; and

Φ = capacity factor for the appropriate action; and

Table V2.1.1a - Annual action models
v2_TabV211a_2019.svg
(iii)

the annual target reliability indices βTG, βTQ, βTW­,… are established as follows:

(A)

For situations where it is appropriate to compare with an equivalent Deemed-to-Satisfy product, a resistance model must be established for the equivalent Deemed-to-Satisfy product and βTG, βTQ, βTW must be calculated for the equivalent Deemed-to-Satisfy product in accordance with Equation 1. The target reliability indices βTG, βTQ, βTW,…thus established, must not be less than those given in Table V2.1.1b minus 0.5.

(B)

For situations where it is not appropriate to compare with an equivalent Deemed-to-Satisfy product, the target reliability index β must be as given in Table V2.1.1b.

Table V2.1.1b - Annual target reliability indices (β)

Type of action

Target reliability index β

Permanent action

4.3

Imposed action

4.0

Wind, snow and earthquake action

3.7

Application of Table V2.1.1b:

Application of Table V2.1.1b:
  1. Table V2.1.1b is applicable for components that exhibit brittle failure similar to concrete as specified in AS 3600.
  2. For components with creep characteristics similar to timber as specified in AS 1720.1, the target reliability index for permanent action shall be increased to 5.0.
  3. The above target reliability indices are based on materials or systems that exhibit creep or brittle failure characteristics similar to timber and concrete. Table V2.1.1b may also be applicable to materials or systems that exhibit creep or brittle failure differently to steel, timber or concrete provided that the creep and/or brittle nature of the material or system are properly accounted for in the design model.
  4. The above target reliability indices are also applicable for materials or systems that exhibit ductile failure characteristics.
(c)

The resistance model for the component must be established by taking into account variability due to material properties, fabrication and construction processes, and structural modelling.

V2.1.2 Structural robustness

Compliance with P2.1.1(a)(iii) is verified for structural robustness by—

(a)

assessment of the structure such that upon the notional removal in isolation of—

(i)

any supporting column; or

(ii)

any beam supporting one or more columns; or

(iii)

any segment of a load bearing wall of length equal to the height of the wall,

the building remains stable and the resulting collapse does not extend further than the immediate adjacent storeys; and

(b)

demonstrating that if a supporting structural component is relied upon to carry more than 25% of the total structure, a systematic risk assessment of the building is undertaken and critical high risk components are identified and designed to cope with the identified hazard or protective measures chosen to minimise the risk.

Explanatory information:

Explanatory information:

V2.1.2 is a means to verify structural robustness of a building or structure in order to meet the requirements of P2.1.1(a)(iii). For further guidance, refer to ABCB Handbook for Structural Robustness.