NCC 2016 Volume One
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Part B1 Structural Provisions (Performance Requirements)

Part B1 Structural Provisions (Performance Requirements)

PERFORMANCE REQUIREMENTS

BP1.1

(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 expect 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

(xiv)

; and

(xv)

termite actions.

consists of two parts:

  • performance attributes that a building is required to have; and
  • a list of actions to be considered in association with these attributes.

Performance attributes

uses the term "with appropriate degrees of reliability” which can be judged with due regard to the possible consequences of failure and the expense, level of effort and procedures necessary to reduce the risk of failure. The measures that can be taken to achieve the appropriate degree of reliability include:

  • choice of a structural system, proper design and analysis;
  • implementation of a quality policy;
  • design for durability and maintenance; and
  • protective measures.

Degrees of reliability of structural elements can be quantified in terms of probabilities of failure with the use of probabilistic models for actions and resistances.

is concerned with the serviceability limit states of buildings in terms of local damage, deformation and vibration. Expected actions are actions with high probabilities of occurrence. The acceptable level of serviceability is subjective. The design for serviceability depends to a large extent on professional judgement. The risk of serviceability failure is, historically, of the order of 10-1 to 10-2.

is concerned with the ultimate limit states of buildings in terms of strength and stability. Extreme actions are actions with low probability of occurrence. Repeated actions are actions, with high frequencies of occurrence in a given time period, that may cause fatigue or other cumulative failures. The notional probability of failure of structural elements is of the order of 10-3 to 10-4 for a 50 year reference period. The probability of structural failure is historically of the order of 10-6 per year.

is concerned with consequences of unspecified actions and is often referred to as "structural robustness". It includes, but is not limited to, progressive collapse. Ways to improve structural robustness include providing redundancies, minimum resistances, protective measures, etc.

is concerned with damage to other properties, which may be caused by reasons other than structural if to are met.

List of actions

lists actions to which a building “may reasonably be subjected”. All possible actions cannot be listed. “Engineering judgement” may need to be used to determine all likely actions and in accessing the likely effects of those actions.

Example

Example

Buildings and structures should be able to withstand the effects of wind, rain or snow. However, they would not be expected to withstand the impact of a crashing aeroplane.

BP1.1(b)(xiv) uses the defined term “construction activity actions”. The term only refers to construction activities that may have an effect on the final design such as stacking or propping. The safety of the building during construction is normally controlled by occupational health and safety authorities.

BP1.2

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

(a)

known construction activities; and

(b)

type of material; and

(c)

characteristics of the site; and

(d)

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

(e)

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

states the principles for the determination of the structural resistance of materials and forms of construction.

It should be noted that the construction activities referred to in may be more than those contained in the defined term of “construction activity actions”. For example, welding of structural steel might cause distortion or change the characteristics of the steel, and hence need to be accounted for. For this reason, the defined term has not been used in .

BP1.3

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

(a)

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

(b)

resists a reasonably foreseeable human impact without breaking; and

(c)

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

Glazing in a building is not always readily visible to all people. It is therefore important to avoid human impact where possible. This may not always be possible. therefore contains three parts:

  • if glazing is broken due to human impact, it must fail in so that small pieces will not cause injury to people (BP1.3(a)).
  • if human impact could occur, the glazing should be of a strength to resist that impact without breaking (BP1.3(b)); and
  • to make it more visible, glazing should be marked with a motive or the like (BP1.3(c)).

BP1.4

(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.

Application

Application:

only applies to—

  1. a Class 2 or 3 building or Class 4 part of a building; and
  2. a Class 9a health-care building; and
  3. a Class 9c building.

only applies to buildings in which people are likely to sleep that are located in a flood hazard area, i.e. a Class 2 or 3 building or a Class 4 part of a building, a Class 9a health-care building or a Class 9c building. A flood hazard area is determined by the appropriate authority (usually the relevant local government) as an area to be affected by flood. The determination is usually via a planning instrument. It is important to note that the NCC provision does not override a provision in a planning instrument which may restrict development in a flood hazard area.

states the principles for the design and construction of the specified buildings in a flood event. The principles include preventing—

  • the buildings suffering structural damage or collapse due to the hydrostatic effect (pressure of still water), or the hydrodynamic effect (force of moving water), or debris impact; and
  • the buildings from being lifted off foundations or footings due to the buoyancy effect; and
  • foundations and footings being affected by scour or erosion caused by moving water; and
  • degradation of structural materials as a result of being immersed in water.