final-report-of-the-advisory-committee-on-falsework-bragg-report - Flipbook - Page 62
The overall factor of safety which we recommend
may well be greater than would have been asssumed
for permanent works. This is because the uncertainty
in loads, both static and dynamic, and the variability
of material used are both likely to be greater in falseworks than in permanent structures. Our recommendation is consistent with recent recommendations of
French structural engineers* as described in records
of the Technical Institute of Building and Public
Works of the National Union of Reinforced Concrete
and Industrial Techniques and the Technical Institute
of Building and Public Works. The work is entitled
'Recommendations for the execution of falsework'.
This recommends a partial safety factor proper to the
material equal to 2 and a second factor which can
range from 1 ·O to 1 · 5 depending on circumstances.
The CIRIA report t recommends rather lower factors
in limit state designs, but these are for permanent
works.
Research and development
One of the terms of reference of the Advisory Committee on Falsework was that it should "recommend
what research and development should be carried out
in the short and long term". It was stated in paragraph
42 of the Interim Report of the committee that
"nothing in the evidence we have received has suggested that there are major gaps in the understanding
of temporary structures". Although the committee
has received a large amount of evidence oral and
written since the Interim Report was published, there
has been no suggestion that this view should be
changed. What has become apparent during the
committee's deliberations is the fact that neither the
existing knowledge nor the results of research are
disseminated widely enough. It is the opinion of the
committee that the results of investigation and
research into failures of falsework are often not
published for the benefit of the construction industry
at large. Such results should reach as large an audience
as possible.
In order that the committee should be aware of both
completed research projects and current research
projects, over 70 questionnaires were sent out to
universities, colleges, polytechnics and other bodies
concerned with research and development in the
construction industry. The vast majority of replies
received indicated that they had no information that
ould be of interest to this committee. The remaining
replies received revealed a narrow spread of investigation and a number of peripheral enquiries which are
mainly aimed either at formwork or at scaffolding,
but which have a bearing on falsework.
Those research projects closely concerning falsework
include:
(a) An investigation into the effect of site factors
on the load capacities of adjustable steel props.
(CIRIA Research Report 27.) This work is
being continued
(b) Research into the pressure of concrete on formwork. This subject has been investigated by a
number of organisations and information on it
has been published by CIRIA. (Research
Report 1.)
(c) Investigations into the loading of bridge falseworks under the control of the Transport and
Road Research Laboratory
(d) A field investigation on behalf of the British
Standard Code of Practice Committee · on
Falsework
( e) Many tests by or on behalf of manufacturers
have been conducted on falsework components
such as props, soldiers, telescopic beams and
towers
(f) Investigations into the strength of military
trestling.
There are several investigations and research projects
either completed or currently in hand which although
not directly falling under the heading falsework will
produce information of value to designers. Examples
of these are:
(a) Investigations into the strength and stability of
scaffold structures, by Dr E Lightfoot, Department of Engineering Science, University of
Oxford
(b) Tests on scaffold couplers, by Dr E Lightfoot,
Department of Engineering Science, University
of Oxford
(c) Investigation concerning the web buckling of
I-beams, by Professor M Holmes, Department
of Civil Engineering, University of Aston,
Birmingham
(d) Structural overload due to impact, by Professor
B Rawlings, Department of Civil and Structural
Engineering, Sheffield University
(e) Rheological early stiffening and early strength
of concrete, by Dr A G B Ritchie, Department
of Civil Engineering, University of Strathclyde,
Glasgow
Although as already stated there are no major gaps in
falsework technology the committee feels that in the
interests of increased safety, progress, and efficient use
of materials and labour, research should commence
in a number of fields. The subjects which warrant
close investigation are:
(a) The horizontal stability of falsework structures
(money has already been set aside by the
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