AS/NZS 1170 Structural design actions

Pieter Zhang
Hello, I am Pieter Zhang, founder of APAC. I have been in the site safety products business for 14 years and the purpose of this article is to share with you the knowledge about site safety products from the perspective of a Chinese supplier.

Part 1: Permanent, imposed and other actions

This Standard specifies permanent, imposed, liquid pressure, groundwater, rainwater ponding and earth pressure actions to be used in the limit state design of structures and parts of structures.
This Standard shall be read in conjunction with AS/NZS 1170.0.
This Standard may be used as a means for demonstrating compliance with the Requirements of Part B1 of the Building Code of Australia.
For the actions covered by this Standard, values for use in design shall be appropriate for
the type of structure or structural element, its intended use, and exposure to such actions.
The determination of values in accordance with Sections 2 to 4 shall be deemed to satisfy this Clause.
The following documents are referred to in this Standard:
AS 1418 Cranes, hoists, and winches (all parts)
1657 Fixed platforms, walkways, stairways, and ladders—Design, construction and
1720 Timber structures
1720.2 Part 2: Timber properties
1735 Lifts, escalators, and moving walks (all parts)
2156 Walking tracks
2156.1 Part 1: Classification and signage
1170 Structural design actions
1170.0 Part 0: General principles
1170.2 Part 2: Wind actions
4332 Non-domestic passenger lifts and goods lifts
Australian Building Codes Board
Building Code of Australia

For the purpose of this Standard, the definitions given in AS/NZS 1170.0 and those below
1.5.1 Imposed action
A variable action resulting from the intended use or occupancy of the structure.
1.5.2 Load
The value of a force appropriate to an action.
1.5.3 Permanent action
Action that is likely to act continuously throughout the design working life and for which
variations in magnitude with time are small compared with the mean value.
1.5.4 Design working life
Assumed period for which a structure or a structural element is to be used for its intended
purpose without major repair being necessary.
1.5.5 Tributary area
The area is assumed to be supported by a structural element.
1.5.6 Variable action
Action for which the variation in magnitude with time is neither negligible in relation to the
mean value nor monotonic.
Unless otherwise stated, the notation used in this Standard has the following meaning:
A = tributary area supported by a structural element
Fe,u = earth pressure action
Fgw = groundwater action
Flp = liquid pressure action
Fpnd = ponding action
G = permanent action
Q = imposed action
ψa = factor for reduction of imposed floor loads due to area
ψl = factor for determining quasi-permanent values (long-term) of actions (see
AS/NZS 1170.0)

Part 2: Permanent Actions

This Section gives permanent actions (G) for use in designing structures.
Permanent actions shall be taken to include the self-weight of the following:
(a) The structure.
(b) All other materials incorporated into the structure.
NOTE: This includes walls, floors, roofs, suspended ceilings and other permanent
construction, as appropriate.
(c) Permanent equipment including fixtures and fittings.
NOTE: This includes permanently fixed wiring, reticulated services and other permanent
equipment as appropriate.
(d) Partitions as given in Clause 2.3.
(e) Stored materials where the resultant actions are consistent with the definition for
permanent action.
The self-weight of a material shall be calculated from the design dimensions or known
dimensions and the unit weight as given in Appendix A.
NOTE: Further information on unit weights of materials is given in AS/NZS 1170.1 Supp 1,
Structural design actions—Permanent, imposed and other actions—Commentary (Supplement to
AS/NZS 1170.1:2002).
The self-weight of permanent partitions shall be calculated for their actual layout.
Structures for which provision is to be made for movable partitions shall be designed for
the anticipated weight of the partitions placed in any probable positions but not less than a
uniformly distributed permanent load of 0.5 kPa over the area being considered.
Consideration shall be given to the actions resulting from the effect of removing those
permanent items that are not essential parts of the structure, such as tanks or their contents,
stored materials as defined in Clause 2.1(e), service equipment, partitions and similar.

Part 3: Imposed Actions

This Section gives imposed actions (Q) for use in designing structures. The values of
imposed actions provided in this Section are appropriate for use with all of the annual
probabilities of exceedance defined in AS/NZS 1170.0.
Actions resulting from construction are not covered in this Standard.
The imposed actions shall be not less than the greater of the following:
(a) The actions resulting from the intended use of the structure.
(b) The imposed actions given in this Section.
NOTE: The imposed actions given in this Section include sufficient allowance for the effects of vertical impact arising from the usual movement of people and shifting of furniture. This
allowance does not cover dynamic effects due to highly active crowds. Dynamic effects due to vibrating machinery are covered separately in Clause 3.7.
The distributed and concentrated imposed loads shall be considered separately and design carried out for the most adverse effect.

A concentrated imposed action shall be applied as follows:
(a) At its known position or where its position is not known, in the position giving the most adverse effect.
(b) Distributed over the actual area of application or if the actual area is not known or otherwise stipulated in Tables 3.1 or 3.2, over an area of not greater than 0.01 m2 for floors and roofs.

The imposed action shall be considered to be absent from any parts of a structure if its
absence will cause more adverse effects on that or any other part. For floor loads, the
intensity of the imposed load shall be appropriate to the loaded portion of the area under
consideration (see Clause 3.4.2).
For design situations involving wind, earthquake or fire emergency conditions, partial
loading of alternate spans of continuous beams or slabs need not be considered.
For partial loading on continuous beams, the span (or two adjacent spans) that contains the
effect under consideration shall be loaded with an imposed load intensity, as determined
from Clause 3.4.2, appropriate to the tributary area supported by the span (or spans). Other
spans that are required to be loaded to cause the most adverse effect shall be assumed to be
loaded with a load intensity appropriate to the span multiplied by the long-term factor (ψl)
given in AS/NZS 1170.0.

3.4.1 Imposed floor actions
The imposed actions (Q) appropriate to the type of activity or occupancy for which the floor
area will be used shall be the reference values given in Table 3.1 and Appendix B
multiplied by the reduction factor given in Clause 3.4.2.

Areas in residential, social, commercial, industrial and administration structures are divided
into seven categories, according to their type of activity or occupancy, as shown in
Column 1 of Table 3.1.
NOTE: The philosophy of the Table is that each area of a floor is associated with one of the
activity types. Thus in order to classify an area under consideration, the design must consider the type of activities that occur in that area.

1 The concentrated load shall be applied over an area of 350 mm2 for calculation of punching or
2 Where a stair tread or landing is structurally independent of the adjoining elements, it shall be capable
of withstanding a line load of 2.2 kN/m of span of tread or landing.
3 A concentrated load of 6.7 kN shall be used where a general allowance for safes is made.
4 The concentrated load shall be applied over an area of 0.025 m2 for calculation of punching or
5 Where these same areas may be subjected to loads due to physical activities or overcrowding (for
example a hotel dining room used as a dance floor), imposed loads shall be based on occupancy C4
or C5, as appropriate.
6 Fixed seating is seating where the removal of the seating and the use of the space for other purposes is
not likely.
7 For domestic garages with timber floors, this may be reduced to 9 kN applied over an area of
0.3 m × 0.3 m.

3.4.2 Reduction of uniformly distributed imposed actions
The reduction factor (ψa) shall be as follows:
(a) ψa = 1.0 for the following:
(i) Areas covered by activity or occupancy types C3, C4 and C5 (see Table 3.1).
(ii) Storage areas on which imposed floor actions exceed 5 kPa.
(iii) Light and medium traffic areas (activity or occupancy types F and G).
(iv) Imposed actions from machinery and equipment for which specific design
allowance has been made.
(v) One-way slabs.
(b) ψa =
A 0.3 + 3 but not greater than 1.0 and not less than 0.5.
A = sum of all areas supported by a structural element, in square metre, for
which reduction is not restricted under Clause 3.4.2(a)

3.5.1 Roofs
Values for the imposed actions appropriate to roofs shall be as given in Table 3.2 except
that roofs used for floor type activities (including activity types A, B, C, D, E, F and G) are
treated as floors and values shall be as given in Table 3.1.
Roofs not accessible except for normal maintenance, repair, painting and minor repairs are
divided into the following categories:
(a) R1—Street awnings or roof areas where it is practical for limited numbers of people
to gain access either from adjacent openable windows, awnings, balconies or roofs or
from the ground only.
(b) R2—Other roofs, either flat or pitched as follows:
(i) Structural elements supporting the cladding.
(ii) Roof cladding inclusive of any associated protective mesh, or similar, which is
required to support actions incidental to maintenance.
(iii) Surfaces (including transparent surfaces) over which supports (e.g., boards or
ladders) are required to be laid to support actions incidental to maintenance
(e.g., people).

1 Structural elements supporting more than 200 m2
of roof area shall be designed to support 0.25 kPa on
the 200 m2
of the supported area that gives the worst effect.
2 A = the plan projection of the surface area of roof supported by the member under analysis, in square metres.
3.5.2 Roof trusses, ceilings, skylights and similar structures
Where the bottom chords of roof trusses, joists and hangers for ceilings, ribs of skylights,
frames and coverings of ceiling access hatches and any similar structure are required to
support the force imposed by a person for any purpose, they shall be designed to support a
1.4 kN concentrated load.
Where the structural element is not required to support a person before the cladding is in
place, and there is headroom of less than 1.2 m after installation of the cladding, the
concentrated action may be reduced to 0.9 kN.
NOTE: This Standard no longer includes the 4.5 kN occasional load on exposed trusses and
beams (for industrial, commercial and farm buildings) that was required in AS 1170.1—1989. If
provision for such loads is required, the loads should be given in the specification for the

Barriers, including parapets, balustrades, and railings, together with members and
connections that provide structural support, shall be designed to sustain the imposed actions given in Table 3.3. The top edge or handrail shall also be designed for the case where a concentrated load of 0.6 kN, positioned for the worst effect, acts inward, outward, or downward.
The uniformly distributed line load and the uniformly distributed and concentrated loads applicable to the infill are not additive. They shall be considered as three separate load cases.
Actions due to wind or earthquake need not be assumed to act concurrently with the loads given in Table 3.3.
NOTE: For the design of barriers for wind effects, information is given in AS/NZS 1170.2.

NOTE: This usage (under B, E) is for access to and safe working at places normally used by operating, inspection,
maintenance, and servicing personnel.

3.7.1 General
Actions resulting from the acceleration of masses in installed cranes, hoists, lifts, and other machinery shall be treated as additional imposed loads.
The imposed loads used for the design of structures supporting such loads shall be—
(a) provided by the manufacturer of that machinery based on an appropriate dynamic
assessment; or
(b) derived from AS 1418, AS 1735, or NZS 4332, as applicable.
In the absence of such information, the factors given in Clauses 3.7.2 and 3.7.3 shall be used.
3.7.2 Vertical actions
For the design of elements supporting lifts, cranes, and machinery, the static vertical actions and their appropriate dynamic factors shall be as given in Table 3.4.

3.7.3 Horizontal actions on crane rails General
The horizontal imposed actions specified in Clauses and shall be considered
as acting at the railhead level, acting together.
Gantry girders and their vertical supports shall be designed on the basis that either of the horizontal imposed actions specified in Clauses or can act at the same time as the vertical load is given in Clause 3.7.2. Transverse to rails
The horizontal imposed actions, acting transverse to crane rails shall be taken as the static wheel load resulting from the combined weight of the crab and the load lifted, multiplied by the following factors:
(a) For electric overhead cranes ………………………………………………………………………0.2.
(b) For hand-operated cranes ………………………………………………………………………..0.05. Parallel to rails
Horizontal imposed actions acting along the rails shall be taken as the static wheel loads
that can occur on the rails, multiplied by the following factors:
(a) For electric overhead cranes ………………………………………………………………………0.1.
(b) For hand-operated cranes ………………………………………………………………………..0.05. Buffer actions
The loads applied to the structure shall be calculated in accordance with AS 1418.

Braking and horizontal impact forces arising from the movement of vehicles shall be treated as additional imposed actions. The imposed braking action shall be half the static load imposed by the gross mass of the vehicle.
The horizontal imposed action on barriers required to withstand the accidental impact from vehicles during parking shall be taken as follows:
(a) For light traffic areas (Type F as given in Table 3.1):
(i) Barriers ……………………………………………………………………………………. 30 kN.
(ii) Barriers at the end of straight ramps exceeding 20 m in length and intended for
downward travel ………………………………………………………………………. 240 kN.
(b) For barriers in medium-traffic areas (Type G as given in Table 3.1)……………… 40 kN.
The impact force shall be distributed over a 1.5 m length at any position along the barrier and shall be assumed to act at 0.5 m above floor level for light traffic areas and at 1.0 m for medium traffic areas.
NOTE: Guidance for situations not covered in this Clause is given in AS/NZS 1170.1 Supp 1,
Structural design actions—Permanent, imposed, and other actions—Commentary (Supplement to
AS/NZS 1170.1:2002).

Grandstands, stadiums, assembly platforms, reviewing stands, and similar, shall be
designed to withstand horizontal imposed actions, in addition to the imposed actions given in Clause 3.4. Horizontal imposed actions due to crowd movement shall be taken as
(a) For platforms with seats, the following separate load cases (not applied
simultaneously), applied at floor level at each row of seats—
(i) 350 N per linear meter of seating along the line of the seats; and
(ii) 150 N per linear meter of seating perpendicular to the line of the seats.
(b) For platforms without seats 250 N per square meter of plan area (0.25 kPa).
The imposed actions of this Clause need not be applied simultaneously to the required
earthquake action.

Part 4: Liquid Pressure, Ground Water, Rainwater Ponding, And Earth Pressure

This Section gives methods for calculating the action of liquids, groundwater, rainwater
ponding and retained earth for use in designed structures.
The action resulting from static liquid pressure (Flp) shall be calculated from the depth of
the liquid and the unit weight of the liquid.
The action resulting from hydrostatic pressure of water acting on surfaces below ground
level (Fgw) shall be the value assuming the water level is at ground level or, where
information is available, the groundwater level with an annual probability of exceedance of
1 in 50.
The action resulting from rainwater ponding (Fpnd) shall be calculated from the expected
ponding and from the quantity of water that can collect when primary drainage does not
function. Both long-term and short-term sag of areas where water may pond shall be taken
into account.
Earth pressure actions (Fe,u) resulting in lateral loads on earth-retaining structures shall be determined using established methods of soil mechanics.

This Appendix gives unit weights of materials for use in calculating self-weight of parts of structures and stored materials.
NOTE: Further information on unit weights of materials is given in AS/NZS 1170.1 Supp 1,
Structural design actions—Permanent, imposed and other actions—Commentary (Supplement to
AS/NZS 1170.1:2002)

1 Mass of masonry includes mass of mortar but not mass of render or plaster, or mass of absorbed rainwater.
2 For mass of fire-rated masonry refer to manufacturer.
3 For most of the boards, values in Column 2 are given only for the given thickness of board. For other thicknesses, proportional values may be taken.

This Appendix gives values of imposed actions for some other specific uses. For all the
specific uses given in this Appendix, the reduction factor (ψa) shall be taken as 1.0.
Table B1 includes values for the following:
(a) Non-habitable structures exposed to the weather in areas that are—
(i) isolated from vehicular access (accessible only by foot over considerable
distances); or
(ii) remote (accessible only by foot where people will have to walk more than 2 days or traverse difficult terrain).
(b) Farm structures (see Notes 1 and 2) that are—
(i) of non-residential occupancy with not more than one person per 30m2 during normal use;
(ii) associated with and located on land devoted to the practice of farming; and
(iii) used essentially for housing equipment or livestock or for production, storage or processing of produce.
1 Examples include hay sheds, implement sheds, grain and fertilizer stores, coolstores for fruit and vegetables, piggeries, poultry sheds, shearing sheds, farm dairies (milking sheds), greenhouses, farm workshops, fruit packing sheds, egg grading rooms, tobacco curing sheds, and garages not attached to the farm residence.
2 Loads due to silos and bunkers are not covered in this Standard.
For the design of walking track structures as defined in AS 2156.1, structures in walking track classifications 3 and 4 shall be designed using the values for isolated structures and in walking track classification 5 using the values for remote structures.

1 The concentrated load shall be applied over an area of 350 mm2 for calculation of punching or crushing.
2 AS 1657 covers fixed platforms, walkways, stairways, and ladders for access to and working at places normally used by operating, inspection, maintenance, and servicing personnel.

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