19.4.2.1 General
The proposed falsework structure should be analysed to find the
parameters that need to be taken into account in the selection of
the individual elements. These parameters include the relevant axial
loads, bending moments, shear forces, bearing stresses and deflection
characteristics.
When considering the reactions on vertical members account should
be taken of any effects of continuity, see 19.3.3.2. Where specific
conditions can be identified, such as beams on three supports, a more
detailed analysis may be justified.
Wherever possible, when detailing the individual elements, the
maximum tolerances permitted for workmanship on site as described
in Clause 20 should be adopted and allowed for in the element design.
For items listed in 20.3.2, the allowable safe working stresses used in
conformity with the recommendations of this code will be adequate.
Where the eccentricity at the point of transfer of loads between
components exceeds the tolerances recommended in 20.3.2, the
connection and the resulting forces should be evaluated and provisions
made for them. Particular care is required when the falsework supports
a soffit with longitudinal and/or transverse crossfalls and where base
plates are supported on a sloping foundation (such as a concrete slab
with a crossfall). Refer to 19.7.7.
Where high concentrations of loading occur on relatively light members,
any problems of local instability due to web crushing and buckling
become more critical. The methods of analysis are outlined in Annex J.
The allowable stresses recommended in this section may be exceeded
by 25% in cases where an increase in stress is solely due to wind forces,
provided that the sections should be not less than those needed if the
wind stresses were neglected.