BS 5975-1:2024 - Book - Page 53
BRITISH STANDARD
BS 5975‑1:2024
12.3 Design guidance
12.3.1
Those responsible for the design of a temporary works scheme should base their design on the
previously agreed design brief (see 12.2).
12.3.2
If the designer is not able to fully accommodate the requirements of the design brief, any proposed
modifications should be drawn to the attention of the PC’s TWC or TWC as appropriate, as soon as the
changes are identified and the design brief amended.
12.3.3
The TWD should choose the appropriate design standards and other technical guidance.
NOTE Where codes of practice are specified by the contract or design brief, the TWD may seek authority to use
other equivalent codes providing equivalent (or better) factors of safety.
12.3.4
The TWD should identify, from the design brief and associated information, the various loads that act
on the temporary works, together with the combinations in which they are considered and with what
stiffness the temporary works are to resist them.
12.3.5
Temporary works should be designed in accordance with recognized engineering principles
(see BS 5975‑2:2024 or other recognized guidance). The design should take into account the
variability of materials, workmanship, site conditions and construction (erection) tolerances.
12.3.6 All temporary works should be designed using global or partial factors appropriate to the situation, taking
into account material quality, certainty of loading and standard of execution of the temporary works.
NOTE 1 Issues that can affect material quality are use of second-hand material and repeated use of components.
NOTE 2 PAS 8812 gives further advice on the application of European standards to the design of temporary works.
12.3.7
For permissible stress design the global factors incorporated into the allowable working loads given
in BS 5975‑2:2024 should be used for general falsework and other temporary work design.
12.3.8
For limit state design of temporary works the the partial factors recommended in BS 5975‑2:2024
should be used. For falsework, the supported loads should be treated as variable actions (imposed
loads) and not as permanent actions (dead loads).
NOTE The loads given in BS 5975-2:2024 are suitable as unfactored service loads for limit state design.
12.3.9
For each temporary works design, the designer should take into account:
a)
the structural strength and stiffness of the individual members and their connections to transmit
the applied forces safely including any P‑Δ or feedback effects;
b)
the lateral stability of both individual members and the structure as a whole;
c)
the resistance to overturning or rotational failure of the temporary works structure;
d)
positional stability; and
e)
the effects on the permanent works and its surroundings.
NOTE 1 Within these five considerations, subsidiary considerations might be necessary to allow for the different
phases of construction and the varying stability and restraint conditions applied, including the particular case
where falsework is designed as top-restrained.
NOTE 2 These five considerations apply to both limit state and permissible stress design.
12.3.10
Where software is used, care should be taken that all appropriate checks are carried out.
12.3.11
Temporary works systems should be designed with regard to ease and safety of erection and
dismantling. TWDs and suppliers should provide guidance on the implementation of their design.
12.3.12
Detailing of the temporary works structure should be such that any local failure within it does not
lead to the progressive collapse of the whole.
© THE BRITISH STANDARDS INSTITUTION 2024 – ALL RIGHTS RESERVED 45
