Part B1 Structural provisions

The Objective of this Part 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.

A building or structure is to withstand the combination of loads and other actions to which it may be reasonably subjected.

(1) Glazing is to be installed in a building to avoid undue risk of injury to people.

(2) Glazing in a building should not cause injury to people due to its failure or people impacting with it because they did not see it.

(1) By resisting the actions to which it may reasonably be expected to be subjected, a building or structure, during construction and use, with appropriate degrees of reliability, must—

1. perform adequately under all reasonably expected design actions; and
2. withstand extreme or frequently repeated design actions; and
3. 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
4. avoid causing damage to other properties.

(2) The actions to be considered to satisfy (1) include but are not limited to—

1. permanent actions (dead loads) including, for a Class 7b building, an additional notional permanent roof load of not less than 0.15 kPa to support the addition of solar photovoltaic panels; and
2. imposed actions (live loads arising from occupancy and use); and
3. wind action; and
4. earthquake action; and
5. snow action; and
6. liquid pressure action; and
7. ground water action; and
8. rainwater action (including ponding action); and
9. earth pressure action; and
10. differential movement; and
11. time dependent effects (including creep and shrinkage); and
12. thermal effects; and
13. ground movement caused by—
    1. swelling, shrinkage or freezing of the subsoil; and
    2. landslip or subsidence; and
    3. siteworks associated with the building or structure; and
14. construction activity actions; and
15. termite actions.

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

1. known construction activities; and
2. type of material; and
3. characteristics of the site; and
4. the degree of accuracy inherent in the methods used to assess the structural behaviour; and
5. action effects arising from the differential settlement of foundations, and from restrained dimensional changes due to temperature, moisture, shrinkage, creep and similar effects.

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

1. if broken on impact, will break in a way that is not likely to cause injury to people; and
2. resists a reasonably foreseeable human impact without breaking; and
3. is protected or marked in a way that will reduce the likelihood of human impact.

(1) 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.

(2) The actions and requirements to be considered to satisfy (1) include but are not limited to—

1. flood actions; and
2. elevation requirements; and
3. foundation and footing requirements; and
4. requirements for enclosures below the flood hazard level; and
5. requirements for structural connections; and
6. material requirements; and
7. requirements for utilities; and
8. requirements for occupant egress.

(1) This Verification Method is applicable to components with a resistance coefficient of variation of at least 10% and not more than 40%.

(2) Where a component has a calculated resistance coefficient of variation of less than 10%, then a minimum value of 10% must be used.

(3) Compliance with B1P1 and B1P2 is verified for the design of a structural component for strength where—

1. the capacity reduction factor

   $\varphi$

   satisfies

   $\varphi \le Average({\varphi }_G,{\varphi }_Q,{\varphi }_W,\mathrm{...})$

   , where

   ${\varphi }_G,{\varphi }_Q,{\varphi }_W,\mathrm{...}$

   are capacity reduction factors for all relevant actions and must contain at least permanent (G), imposed (Q) and wind (W) actions; and
2. the capacity reduction factors

   ${\varphi }_G,{\varphi }_Q,{\varphi }_W,\mathrm{...}$

   are calculated for target reliability indices for permanent action

   ${\beta }_{TG}$

   , for imposed action

   ${\beta }_{TQ}$

   , for wind action

   ${\beta }_{TW}$

   ,… in accordance with the equation:

   $\beta =\ln \left[\left(\frac{\overline{R}}{\overline{S}}\right)\sqrt{\frac{C_S}{C_R}}\right]/\sqrt{\ln (C_R.C_S)}$

   , where—

   1. $\left(\frac{\overline{R}}{\overline{S}}\right)=\frac{\left(\frac{\gamma }{\varphi }\right)}{\left(\frac{\overline{S}}{S_N}\right)}\left(\frac{\overline{R}}{R_N}\right)$

      ; and

   2. $\begin{array}{l}{C}_R=1+V_R^2\\ C_S=1+V_S^2 \end{array}$

      , where—

      1. $\frac{\overline{R}}{R_N}$

         = ratio of mean resistance to nominal; and

      2. $\frac{\overline{S}}{S_N}$

         = ratio of mean action to nominal; and

      3. $C_S$

         = correction factor for action; and

      4. $C_R$

         = correction factor for resistance; and

      5. $V_S$

         = coefficient of variation of the appropriate action as given in Table B1V1a; and

      6. $V_R$

         = coefficient of variation of the resistance; and

      7. $\gamma$

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

      8. $\varphi$

         = capacity factor for the appropriate action; and
3. the annual target reliability indices

   ${\beta }_{TG},{\beta }_{TQ},{\beta }_{TW},\mathrm{...}$

   are established as follows:
   1. For situations where it is appropriate to compare an equivalent Deemed-to-Satisfy product, a resistance model must be established for the equivalent Deemed-to-Satisfy product and

      ${\beta }_{TG},{\beta }_{TQ},{\beta }_{TW},\mathrm{...}$

      must be calculated for the equivalent Deemed-to-Satisfy product in accordance with the equation given at (b).
   2. The target reliability indices

      ${\beta }_{TG},{\beta }_{TQ},{\beta }_{TW},\mathrm{...}$

      thus established, must be not less than those given in Table B1V1b minus 0.5.
   3. For situations where it is not appropriate to compare with an equivalent Deemed-to-Satisfy product, the target reliability index

      $\beta$

      must be as given in Table B1V1b.

(4) 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.

(1) Compliance with B1P1(1)(c) is verified for structural robustness if (2) and (3) are complied with.

(2) The structure is assessed such that the building remains stable and the resulting collapse does not extend further than the immediately adjacent storeys upon the notional removal in isolation of—

1. any supporting column; or
2. any beam supporting one or more columns; or
3. any segment of a load bearing wall of length equal to the height of the wall.

(3) It is demonstrated 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.

(1) Where a Deemed-to-Satisfy Solution is proposed, Performance Requirements B1P1 to B1P4 are satisfied by complying with B1D2 to B1D6.

(2) Where a Performance Solution is proposed, the relevant Performance Requirements must be determined in accordance with A2G2(3) and A2G4(3) as applicable.

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

1. the most critical action effect on a building or structure is determined in accordance with B1D3 and the general design procedures contained in AS/NZS 1170.0; and
2. the resistance of a building or structure is determined in accordance with B1D4.

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

1. Permanent actions:
   1. the design or known dimensions of the building or structure; and
   2. the unit weight of the construction; and
   3. AS/NZS 1170.1; and
   4. for a Class 7b building, a notional additional permanent roof load of not less than 0.15 kPa to support the addition of solar photovoltaic panels.
2. Imposed actions:
   1. the known loads that will be imposed during the occupation or use of the building or structure; and
   2. construction activity actions; and
   3. AS/NZS 1170.1.
3. Wind, snow and ice and earthquake actions:
   1. the applicable annual probability of design event for safety, determined by—
      1. assigning the building or structure an Importance Level in accordance with Table B1D3a; and
      2. determining the corresponding annual probability of exceedance in accordance with Table B1D3b; and
   2. AS/NZS 1170.2; and
   3. AS/NZS 1170.3 as appropriate; and
   4. AS 1170.4 as appropriate; and
   5. in cyclonic areas, metal roof cladding, its connections and immediate supporting members must comply with Specification 4; and
   6. for the purposes of (v), cyclonic areas are those determined as being located in wind regions C and D in accordance with AS/NZS 1170.2.
4. Actions not covered in (a), (b) and (c) above:
   1. the nature of the action; and
   2. the nature of the building or structure; and
   3. the Importance Level of the building or structure determined in accordance with Table B1D3a; and
   4. AS/NZS 1170.1.
5. For the purposes of (d) the actions include but are not limited to—
   1. liquid pressure action; and
   2. ground water action; and
   3. rainwater action (including ponding action); and
   4. earth pressure action; and
   5. differential movement; and
   6. time dependent effects (including creep and shrinkage); and
   7. thermal effects; and
   8. ground movement caused by—
      1. swelling, shrinkage or freezing of the subsoil; and
      2. landslip or subsidence; and
      3. siteworks associated with the building or structure; and
   9. construction activity actions.

The structural resistance of materials and forms of construction must be determined in accordance with the following, as appropriate:

1. Masonry (including masonry-veneer, unreinforced masonry and reinforced masonry): AS 3700, except—
   1. ‘(for piers—isolated or engaged)’ is removed from Clause 8.5.1(d); and
   2. where Clause 8.5.1 requires design as for unreinforced masonry in accordance with Section 7, the member must also be designed as unreinforced masonry in accordance with Tables 10.3 and 4.1(a)(i)(C) of AS 3700.
2. Concrete:
   1. Concrete construction (including reinforced and prestressed concrete): AS 3600.
   2. Autoclaved aerated concrete: AS 5146.1 and AS 5146.3.
   3. Post-installed and cast-in fastenings: AS 5216.
3. Steel construction:
   1. Steel structures: AS 4100.
   2. Cold-formed steel structures: AS/NZS 4600.
   3. Residential and low-rise steel framing: NASH Standard – Residential and Low-Rise Steel Framing Part 1 or Part 2.
4. Composite steel and concrete: AS/NZS 2327.
5. Aluminium construction: AS/NZS 1664.1 or AS/NZS 1664.2.
6. Timber construction:
   1. Design of timber structures: AS 1720.1.
   2. Timber structures: AS 1684.2, AS 1684.3 or AS 1684.4.
   3. Nailplated timber roof trusses: AS 1720.5.
7. Piling: AS 2159.
8. Glazed assemblies:
   1. The following glazed assemblies in an external wall must comply with AS 2047:
      1. Windows excluding those listed in (ii).
      2. Sliding and swinging glazed doors with a frame, including french and bi-fold doors with a frame.
      3. Adjustable louvres.
      4. Shopfronts.
      5. Window walls with one piece framing.
   2. All glazed assemblies not covered by (i) and the following glazed assemblies must comply with AS 1288:
      1. All glazed assemblies not in an external wall.
      2. Revolving doors.
      3. Fixed louvres.
      4. Skylights, roof lights and windows in other than the vertical plane.
      5. Sliding and swinging doors without a frame.
      6. Windows constructed on site and architectural one-off windows, which are not design tested in accordance with AS 2047.
      7. Second-hand windows, re-used windows and recycled windows.
      8. Heritage windows.
      9. Glazing used in balustrades and sloping overhead glazing.
9. Termite Risk Management: Where a primary building element is subject to attack by subterranean termites: AS 3660.1, and—
   1. for the purposes of this provision, a primary building element consisting entirely of, or a combination of, any of the following materials is considered not subject to termite attack:
      1. Steel, aluminium or other metals.
      2. Concrete.
      3. Masonry.
      4. Fibre-reinforced cement.
      5. Timber — naturally termite resistant in accordance with Appendix C of AS 3660.1.
      6. Timber — preservative treated in accordance with Appendix D of AS 3660.1; and
   2. a durable notice must be permanently fixed to the building in a prominent location, such as a meter box or the like, indicating—
      1. the termite management system used; and
      2. the date of installation of the system; and
      3. where a chemical is used, its life expectancy as listed on the appropriate authority’s pesticides register label; and
      4. the installer’s or manufacturer’s recommendations for the scope and frequency of future inspections for termite activity.
10. Roof construction (except in cyclonic areas):
    1. Terracotta, fibre-cement and timber slates and shingles: AS 4597.
    2. Roof tiling: AS 2050.
    3. Cellulose cement corrugated sheets: AS/NZS 2908.1 with safety mesh installed in accordance with AS 1562.3 clause 2.4.3.2 except for sub-clause (c)(vii) for plastic sheeting.
    4. Metal roofing: AS 1562.1.
11. Particleboard structural flooring: AS 1860.2.
12. 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 AS/NZS 1170.2: AS/NZS 4505.
13. Lift shafts which are not required to have an FRL, must—
    1. except as required by (ii), be completely enclosed with non-perforated material between the bottom of the pit and the ceiling of the lift shaft, other than—
       1. at landing doors, emergency doors and pit access doors; and
       2. low-rise, low-speed constant pressure lifts; and
       3. small-sized, low-speed automatic lifts; and
    2. in atrium and observation areas, be protected with non-perforated material not less than 2.5 m in height—
       1. above any places on which a person can stand, which are within 800 mm horizontal reach of any vertical moving lift component including ropes and counterweights; and
       2. at the lowest level of the atrium area that the lift serves, on all sides except the door opening, for not less than 2.5 m in height, by enclosure with non-perforated material; and
    3. be of non-brittle material; and
    4. where glazing is used—
       1. comply with Table B1D4; or
       2. not fail the deflection criteria required by S6C11(c)(iii).

(1) 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 BCA, 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.

(2) Structural software referred to in (1) can only be used for buildings within the following geometric limits:

1. The distance from ground level to the underside of eaves must not exceed 6 m.
2. The distance from ground level to the highest point of the roof, neglecting chimneys, must not exceed 8.5 m.
3. The building width including roofed verandahs, excluding eaves, must not exceed 16 m.
4. The building length must not exceed five times the building width.
5. The roof pitch must not exceed 35 degrees.

(3) The requirements of (1) do not apply to design software for individual frame members such as electronic tables similar to those provided in—

1. AS 1684; or
2. NASH Standard Residential and Low-Rise Steel Framing Part 2.

(1) A building in a flood hazard area must comply with the ABCB Standard for Construction of Buildings in Flood Hazard Areas.

(2) The requirements of (1) only apply to a Class 2 or 3 building, Class 9a health-care building, Class 9c building or a Class 4 part of a building.