HSE
Health & Safety
Executive
Friction in temporary works
Prepared by the
University of Birmingham
for the Health and Safety Executive 2003
RESEARCH REPORT 071
HSE
Health & Safety
Executive
Friction in temporary works
Dr N J S Gorst, Dr S J Williamson,
Eur Ing P F Pallett and Professor L A Clark
School of Engineering
The University of Birmingham
Edgbaston
Birmingham
B15 2TT
United Kingdom
During initial assembly, temporary works often rely upon friction to provide lateral stability. Frictional
resistance is also utilised in temporary works design as a means of transferring horizontal forces
through falsework or formwork to points of restraint.
The results are presented of an investigation to verify existing claimed values of static coefficient of
friction and to establish practical values of the coefficient for the latest commonly used materials in
temporary works. Friction tests were undertaken on 260 combinations of different material faces used
in temporary works, including both "dry" and saturated timber. The tests generated data for
combinations for which no codified data exist and also generated data which could be compared with
existing British and German codified data.
For material combinations for which codified data exist, the friction values obtained in the current
research tended to lie between the maximum and minimum bound code values, but closer to the
minimum values. Recommendations are made for code friction values for all material combinations. It
is considered that further research is required to investigate the variation in some measured friction
values.
This report and the work it describes were funded by the Health and Safety Executive. Its contents,
including any opinions and/or conclusions expressed, are those of the authors alone and do not
necessarily reflect HSE policy.
HSE BOOKS
© Crown copyright 2003
First published 2003
ISBN 0 7176 2613 X
All rights reserved. No part of this publication may be
reproduced, stored in a retrieval system, or transmitted in
any form or by any means (electronic, mechanical,
photocopying, recording or otherwise) without the prior
written permission of the copyright owner.
Applications for reproduction should be made in writing to: Licensing Division, Her Majesty's Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by e-mail to [email protected]
ii
CONTENTS
CONTENTS ...............................................................................................................iii 1.
INTRODUCTION........................................................................................................ 1
2.
THEORY AND CURRENT INFORMATION .....................................................3
3.
EXPERIMENTAL PROCEDURES .....................................................................7
4.
RESULTS .............................................................................................................13
5.
COMPARISON OF RESULTS WITH CURRENT INFORMATION..................19
6.
CONCLUSIONS...................................................................................................21
7.
RECOMMENDATIONS ......................................................................................23
8.
ACKNOWLEDGEMENTS ....................................................................................... 25 9.
REFERENCES ........................................................................................................... 27 ABBREVIATIONS ............................................................................................................... 29 APPENDIX A
Friction Test Data ............................................................................ 31 APPENDIX B
Saturation Test Data ........................................................................ 53
iii
iv
SUMMARY
Friction tests were undertaken on 260 combinations of different material faces used in temporary
works, including both "dry" and saturated timber. The tests generated data for combinations for
which no codified data exist and also generated data which could be compared with existing
British and German codified data.
For material combinations for which codified data exist, the friction values obtained in the
current research tended to lie between the maximum and minimum bound code values, but closer
to the minimum values.
Recommendations are made for code friction values for all material combinations.
It is considered that further research is required to investigate the variation in some measured
friction values.
v
vi
1 INTRODUCTION Temporary works of falsework and soffit formwork include arrangements of multiple levels of
bearers, beams and grillages. Often these members are seated on each other with little or no
positive connection. Lateral stability is an important consideration in all temporary works
structures and, during the initial assembly, temporary works often rely upon friction to provide
such stability.
Frictional resistance is often used in temporary works design calculations as the means of
transferring horizontal forces through the structure to points of suitable restraint.
This project was carried out as a result of a recommendation from The Health and Safety
Executive (HSE) report "Falsework Design – Comparative Calculations" (Ref 1) which required
that confidence be established in the existing proposed values for friction. The aim of the work
was to verify existing claimed values of static coefficient of friction and to establish practical
values of the coefficient for the latest commonly used materials in temporary works. The main
experimental work was completed in December 1999. Following comments from industry it was
decided to extend the experimental work to include a second phase, which would investigate
friction on wet timber.
1
2
2 THEORY AND CURRENT INFORMATION When two items are placed one on top of the other and are not in motion there is a certain value
of lateral force which can be resisted across the interface. In theory this force is a constant ratio
of the applied load, is dependent on the materials in contact and is independent of the contact
area; the ratio is known as the coefficient of static friction. The coefficient of static friction is
given by the expression (see Figure 1):
m=
where:
Ff
R
=
W sinq
= tanq
W cosq
[1]
R is the reaction force normal to the surface (N)
Ff is the limiting value of the frictional force (N)
W is the vertically applied force (N)
q is the minimum angle from the horizontal, for a particular pair of materials
at which sliding will commence
W
Ff
P
R
q
Figure 1 Restraint provided by friction
In practice it has been found that measured values of the coefficient can vary widely. It has been
suggested that the coefficient is in fact a function of the load and that it may be affected by the
location of the member, i.e. whether it is the upper load bearing member or the lower load
receiving member. Values of coefficient of static friction recommended in Table 19 of BS
5975:1996 (Ref 2), Table 1, indicate that the coefficient is independent of member location.
3
Table 1: Minimum value of coefficient of static friction, BS 5975:1996 (Ref 2)
Lower load-accepting
member
Upper load-accepting member
Plain steel
Painted steel
Concrete
Softwood
timber
Hardwood
Plain steel
0.15
0.1
0.1
0.2
0.1
Painted steel
0.1
0.0
0.0
0.2
0.0
Concrete
0.1
0.0
0.4
0.4
0.3
Softwood timber
0.2
0.2
0.4
0.4
0.3
Granular soil
0.3
0.3
0.4
0.3
0.3
Hardwood
0.1
0.0
0.3
0.3
0.1
The current UK Code of Practice, BS 5975:1996 (Ref 2) on falsework gives values for guidance
on friction for a few materials only and friction values have remained unaltered since its first
publication in 1982. It has not been possible to find the origin of these values.
In April 1997 the European Draft, prEN 12812 (Ref 3) on performance and general design of
falsework was published for comment. Many of the diagrams and content are copied from the
original Table 7 in German standard DIN 4421 (Ref 4). The German standard quotes minimum
and maximum values of coefficient of static friction: these are reported in Table 2. It is
understood that the DIN 4421 values were from research by Professor Mohler, at Karslruhe
University. Comparison of the English and German data shows that the British values agree quite
well with the German minimum values.
4
Table 2: Friction coefficients, m, from German Standard DIN 4421 (Ref 4) and
prEN 12812 (Ref 3)
Building material combination
Friction coefficient, m
Maximum
Minimum
1
wood / wood (rubbing surfaces parallel to grain or at right
angles to grain)
1.0
0.4
2
wood / wood (one or both rubbing surfaces at right angles to
grain (cross cut) or end grain)
1.0
0.6
3
wood / steel
1.2
0.5
4
wood / concrete
wood / mortar bed
1.0
0.8
5
steel / steel
0.8
0.2
6
steel / concrete
0.4
0.3
7
steel / mortar bed
1.0
0.5
8
concrete / concrete
1.0
0.5
The committee drafting the European Standard (CEN/TC53/WG6, Falsework) expects to have
published a European standard shortly, which will see the withdrawal in the UK of BS 5975 and
any of the conflicting information, such as the table on friction coefficients.
The future design of falsework will almost certainly require a specific calculation for positional
stability, and a detailed check for sideways restraint using friction will be a requirement for all
falsework calculations.
If reliable friction values do not exist, and fixings between members are specified, they will
involve both man-hours for assembly and dismantling, and the use of expendable items such as
bolts or nails. Of greater concern is the likely reduction in quality and/or re-use potential of the
equipment. Items with drilled holes for bolted connections will reduce their load carrying
capacity, and, in the case of extensive nailing, may be reduced to scrap. The use of more accurate
friction values will lead to a reduction in the number of positive connections required and hence
reduced erection and dismantling times, lower labour costs and extended life of temporary works
items.
5
6
3 EXPERIMENTAL PROCEDURES The originally specified test combinations are presented in Table 3. It was agreed with the HSE
that the tests with fresh concrete as one member would not be carried out, simply because of the
extra variability in results which would be introduced by factors such as mix type, age and test
method.
It was originally envisaged that each material combination would be tested three times at three
load levels (0kg, 25kg, 50kg) and with members in both the upper and lower position. Once
testing was underway, however, it appeared that three load levels and alternating positions were
not necessary. This allowed the original programme to be reduced and permitted tests of extra
combinations to be undertaken; the extent of this testing is indicated in Table 4.
Coefficient of friction was measured by placing the two materials on a tilting table, illustrated in
Figure 2. The table was raised manually by winding the handle, which operated a jack situated
below the table. In order to avoid inconsistencies caused by change of operator a constant
winding speed of approximately 60 rpm (equivalent to about 34o per minute) was agreed after
preliminary testing. The table was raised until the point where slip occurred was reached and the
angle at slip was recorded. A list of the materials used and their sources can be found in Table 5.
Figure 2 Test rig
7
Table 3: Coefficients of static friction (m) for originally specified test combinations
Lower load-accepting member
Upper load-bearing member
Plain steel
Max
Min
Galv. Steel
Max
Min
Painted steel
Max
Min
Aluminium
Max
Min
Wet concrete
Max
Min
0.8
0.15
tba
tba
tba
0.1
tba
tba
0.4
0.1
tba
Painted or oiled steel
tba
0.1
tba
tba
0.0
0.0
tba
tba
tba
0.0
Aluminium
tba
tba
tba
tba
tba
tba
tba
tba
tba
Softwood timber – rubbing surface
parallel to the grain
1.2
0.2
tba
tba
1.2
0.2
tba
tba
Softwood timber – rubbing surface
right angle to the grain or on end
grain
1.2
0.2
tba
tba
1.2
0.2
tba
Hardwood timber – rubbing surface
parallel to the grain
tba
0.1
tba
tba
tba
0.0
Hardwood timber – rubbing surface
right angle to the grain or on end
grain
tba
0.1
tba
tba
tba
Proprietary timber
tba
tba
tba
tba
Plywood
tba
tba
tba
tba
Plain steel
Hard concrete
Max
Min
Softwood
Max
Min
Hardwood
Max
Min
Prop. Timber
Max
Min
Plywood
Max
Min
tba
1.2
0.2
tba
0.1
tba
tba
tba
tba
tba
tba
tba
tba
tba
0.0
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
1.0
0.4
tba
tba
1.0
0.4
tba
0.3
tba
tba
tba
tba
tba
1.0
0.4
tba
tba
1.0
0.4
tba
0.3
tba
tba
tba
tba
tba
tba
1.0
0.3
tba
tba
tba
0.3
tba
0.1
tba
tba
tba
tba
0.0
tba
tba
1.0
0.3
tba
tba
tba
0.3
tba
0.1
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
tba
Galvanised steel
Note:
Values of coefficients taken from BS 5975 Table 19 (Ref 2) and prEN 12812 Table 7 (Ref 3)
Where not known, i.e. to be determined in current study, shown as tba
8
Table 4a: Material combinations tested
Upper Load-Bearing Member
Lower Load-Accepting
Member
Steel
Alum.
Timber
Softwood
Steel
Plain
unrusted
Plain
unrusted
Plain
rusted
Galv.
·
¨
·
¨
¨
Plain rusted
Alum.
Timber
Prop.
painted
Prop.
waling
·
·
Dry
Wet
Par.
Perp.
Par.
·x
·x
+
Galvanised
·
¨
·
·
·
·
·
·
¨
·
·
·
·
·
·
¨
·
·
·
·
·
·
·
·
·x
·x
·
¨
·
·
·
·
Prop. beam
Wet
Par.
Perp.
Par.
·
·
+
Perp.
Reused
·
·
+
·
·
+
·
·
·
·
+
·
Dry
Wet
·
·
+
Combi
ply
faced
Film
faced
Finnish
Film
faced
quality
¨
¨
·
·
+
·
·
+
·
·
¨
·
·
¨
·
·
¨
·
·
¨
+
·
Good one
side
New
+
¨
+
¨
+
·
+
Prop. beam
– reused
Prop. beam
– new
Perp.
+
·
Dry
+
Prop.
painted
Prop.
waling
Dry
softwood
Wet
softwood
Dry
hardwood
Wet
hardwood
Plywood
Hardwood
+
¨
·
¨
·
·
·
¨
X
Tests required by original programme
Additional tests required by modified programme
Tests repeated with ‘planed all round’ softwood
+
Additional test with saturated timber
·
·x
·x
·
9
·
Table 4b: Material combinations tested
Upper Load-Bearing Member
Lower Load-Accepting
Member
Steel
Alum.
Timber
Softwood
Plywood
Hardened
Concrete
dry good
one side
wet good
one side
Combi ply
faced
Film faced
Finnish
Film faced
quality
used film
face
trowelled
face
Plain
unrusted
Plain
rusted
Galv.
·
¨
·
Prop.
painted
Prop.
waling
·
·
Dry
Hardwood
Wet
Par.
Perp.
·x
·x
Par.
Plywood
Perp.
Dry
Wet
Par.
Perp.
·
·
Par.
·
+
¨
·
Perp.
Proprietary
beam
ReNew
used
Good one
side
Dry
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
¨
·
·
·
·
·
¨
¨
cast face
·
¨
X
Tests required by original programme
Additional tests required by modified programme
Tests repeated with ‘planed all round’ softwood
+
Additional test with saturated timber
¨
+
10
¨
·
·
¨
¨
Film
faced
quality
¨
+
¨
¨
Film
faced
Finnish
·
¨
¨
Wet
Combi
ply
faced
¨
¨
¨
¨
¨
¨
·
·
¨
¨
+
¨
¨
¨
Table 5: Materials used in the test programme
Material
Plain unrusted steel
Plain rusted steel
Proprietary painted steel
Galvanised steel
Aluminium
Softwood – rough cut
Softwood – planed all round
Hardwood
Proprietary timber
Plywood – good one side
Plywood
Concrete
Trade Name
--Multijoist
-Alform
--GT24
-Beto film, Wisaform,
Wisaform special
--
Source
University of Birmingham
University of Birmingham
RMD – Kwikform Ltd
University of Birmingham
RMD – Kwikform Ltd
University of Birmingham
University of Birmingham
University of Birmingham
PERI Ltd
University of Birmingham
Kymmene Schauman
University of Birmingham
On completion of the main test programme and consideration of the data with the HSE, it was
deemed pertinent to carry out two further test programmes to investigate the effect of member
position and the effects of time and/or bedding effects on friction values. These two additional
test programmes utilised two material pairs: plain unrusted steel/ proprietary painted steel and
aluminium/plywood.
The effect of time on coefficient of friction was investigated by performing a zero load test,
leaving the test set-up for two days then repeating the test. The effect of bedding on coefficient of
friction was investigated by performing a loaded test, leaving the test set-up for two days then
repeating the test.
Following comments from industry it was decided to extend the experimental work to include a
further phase, which would investigate friction on wet timber. In order to produce saturated
timber specimens, timber test specimens were stored underwater and the level of surface
saturation was monitored over time by taking three measurements of surface moisture content
using a commercial moisture meter. A timber specimen was deemed to be saturated, and thus
ready for friction testing, when the measurements of surface moisture content remained
approximately constant over time. The saturated timber samples were stored in water between
individual friction tests and were only removed from the water immediately before the start of a
test.
11
12
4 RESULTS The main body of results is presented in Table 6a and Table 6b on pages 14 and 15. Each piece of
data from the current study included in this table is the average of three tests; the raw data can be
found in Appendix A. The second line of values present in some cells of Table 6 are coefficients
measured using a planed softwood as one member rather than the rougher softwood used in other
tests. The rough softwood is more representative of that found on site.
The raw data for the saturation phase of the experimental work is contained in Appendix B. It is
emphasised that the tabulated data have not been corrected for timber species and are intended
simply to demonstrate that "saturation" had been achieved.
It was observed that the value of coefficient of friction was generally independent of member
position (upper or lower). Hence, tests on pairs of materials were not repeated with each member
in both the upper and lower position. On examination of the final results, however, it appears
that, of the thirty-six pairs which were tested with each member in both upper and lower
positions, eight are affected by location. The affected pairs are presented in Table 7.
Table 7: Combinations where coefficient of friction was affected by member position
Member 1
Member 2
Member 1 – Upper
Member 2 - Lower
Max
Min
Member 2 – Upper
Member 1 - Lower
Max
Min
Plain unrusted steel
Prop. painted steel
0.4
0.3
0.6
0.5
Plain rusted steel
Galvanised steel
0.6
0.4
0.4
0.3
Plain unrusted steel
Softwood
0.4
0.3
0.6
0.5
Prop. painted steel
Hardwood
0.7
0.5
0.5
0.4
Plain rusted steel
Plywood
0.6
0.4
0.4
0.3
Aluminium
Prop. timber (new)
0.4
0.2
0.5
0.5
Aluminium
Plywood
0.5
0.3
0.3
0.2
In order to investigate this behaviour, the further tests given in Table 8 were carried out. These
measured the friction values for pairs of (a) plain unrusted steel and proprietary painted steel and
(b) aluminium and plywood. In both cases the pair were tested on both faces and in both upper
and lower position. The apparent location dependence of the friction value was not manifested in
the further test data, although slightly different values were obtained depending on which face
was used. The results of the further tests suggest that the initial variations may either have been
simply due to the natural scatter in friction values, or that different specimen faces with slightly
different surface qualities were used when members were in the upper and lower positions, or a
combination of both these factors. Hence, any future test programme with more replicate
specimens would improve the reliability of the friction values obtained.
13
Table 6a – Coefficients of static function obtained from current study
Upper Load-Bearing Member
Lower Load-Accepting
Member
Steel
Alum.
Timber
Softwood
Steel
Plain
unrusted
Plain rusted
Timber
Plain
rusted
Galv.
0.4
0.3
0.5
0.4
0.3
0.3
0.5
0.4
0.6
0.4
0.7
0.6
0.5
0.3
0.4
0.3
0.3
0.2
0.4
0.4
0.4
0.2
--
Prop.
painted
Prop.
waling
0.6
0.5
Dry
0.2
0.1
Perp.
Reused
New
Dry
Wet
0.4
0.3
0.6
0.5
(0.5)
0.4
0.4
(0.3)
0.7
0.7
--
0.5
0.5
0.5
0.5
0.7
0.6
--
--
0.5
0.5
0.4
0.3
0.6
0.5
--
--
--
--
--
--
0.8
0.8
--
--
--
0.8
0.8
--
--
--
--
--
--
0.5
0.5
0.8
0.7
0.5
0.4
0.4
0.2
0.4
0.4
0.4
0.2
0.5
0.4
0.5
0.4
0.4
0.4
0.7
0.6
(0.5)
0.5
0.5
0.7
0.4
0.5
0.4
0.6
0.5
(0.3)
0.5
0.5
0.5
0.4
0.5
0.4
0.5
0.5
0.6
0.5
0.5
0.3
0.4
0.4
--
--
--
--
--
--
0.5
0.4
0.6
0.6
0.5
0.5
0.7
0.5
0.4
0.4
--
--
--
--
--
--
0.6
0.6
--
--
-0.4
0.2
0.6
0.5
(0.6)
Film
faced
quality
Par.
0.5
0.5
KEY:
Film
faced
Finnish
Perp.
0.5
0.4
0.5
0.4
Combi
ply
faced
Par.
--
0.5
0.4
Good one
side
Perp.
0.4
0.3
0.6
0.5
Prop. beam
Wet
Par.
Dry
softwood
Prop. beam
- new
Dry
Perp.
Prop.
painted
Prop.
waling
Wet
softwood
Dry
hardwood
Wet
hardwood
Prop. beam
- reused
Hardwood
Wet
Par.
0.4
0.3
0.4
0.3
0.3
0.2
Galvanised
Alum.
Plain
unrusted
Plywood
0.6
0.5
-0.8
0.7
0.6
0.6
----
-0.9
0.9
0.7
0.6
--
--
--
--
--
--
0.4
0.4
0.6
0.5
0.5
0.5
0.4
0.3
0.2
0.2
0.5
0.5
0.3
0.2
--
--
--
0.7
0.7
--
--
--
--
--
-0.1
0.1
0.3
0.2
0.2
0.1
--
--
0.5
0.4
0.5
0.4
--
--
--
0.6
0.5
0.3
0.3
--
--
--
0.2
0.2
--
1.1
0.9
0.9
0.9
--
--
0.8
0.8
1.0
0.7
--
--
--
--
--
--
--
0.5
0.5
0.4
0.4
--
--
0.5
0.4
0.5
0.5
--
--
--
0.5
0.4
0.3
0.3
--
--
--
0.2
0.2
--
--
--
--
--
--
0.8
0.8
0.9
0.8
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
0.5
0.4
(0.5)
0.4
0.3
(0.4)
--
--
0.4
0.4
0.4
0.4
--
--
--
0.5
0.5
0.3
0.3
--
--
--
0.2
0.2
Maximum value
Minimum value
Values for softwood planed all round
14
Table 6b – Coefficients of static function obtained from current study
Upper Load-Bearing Member
Lower Load-Accepting
Member
Steel
Alum.
Timber
Softwood
Plywood
Hardened
Concrete
Dry good
one side
Wet good
one side
Combi ply
faced
Film faced
Finnish
Film faced
quality
Used film
face
Trowelled
face
Cast face
--
--
--0.1
0.1
-0.6
0.5
--
KEY:
0.2
0.2
0.2
0.2
0.2
0.2
0.6
0.4
0.7
0.7
-0.6
0.5
(0.6)
--0.2
0.1
0.3
0.3
0.3
0.2
--
Film
faced
quality
Perp.
Par.
Perp.
Par.
Perp.
Reused
New
Dry
Wet
0.5
0.3
0.3
0.2
(0.4)
0.4
0.3
(0.2)
--
--
0.3
0.3
0.4
0.3
--
--
--
0.4
0.3
0.5
0.3
--
--
--
0.3
0.2
--
--
--
--
--
--
--
--
0.9
0.8
0.8
0.7
--
--
--
--
--
--
--
0.2
0.2
0.2
0.2
0.3
0.1
0.4
0.3
0.7
0.6
0.3
0.2
0.4
0.2
0.1
0.1
0.3
0.3
0.6
0.4
0.3
0.2
0.3
0.3
0.2
0.2
0.5
0.5
1.1
1.0
0.8
0.8
0.2
0.2
0.4
0.2
0.2
0.1
0.3
0.3
0.8
0.7
0.7
0.7
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
--
0.2
0.2
0.2
0.2
--
0.6
0.4
Film
faced
Finnish
Par.
0.4
0.4
0.4
0.3
Good one
side
Perp.
0.2
0.2
Galv.
Prop. beam
Par.
Prop.
waling
Plain
rusted
Hardwood
Combi
ply
faced
Prop.
painted
Plain
unrusted
Plywood
--
--
Dry
Wet
---0.9
0.8
Maximum value
Minimum value
Values for softwood planed all round
15
Dry
----
Wet
--
--
0.7
0.7
0.6
0.5
0.8
0.6
0.7
0.7
--
--
--
--
--
--
--
--
-0.4
0.4
0.8
0.8
--
-0.2
0.1
0.4
0.4
0.7
0.6
--
0.3
0.2
0.3
0.2
0.2
0.2
0.3
0.3
0.4
0.3
0.4
0.3
--
--
--
0.2
0.2
--
--
--
--
--
--
--
--
0.7
0.6
0.3
0.3
0.3
0.3
0.2
0.2
Table 8 Investigation of effect of member position (upper/lower)
Lower Member Upper Member
Plain unrusted steel (face 1)
Prop. painted steel (face 1)
Plain unrusted steel (face 2)
Prop. painted steel (face 2)
Aluminium (face 1)
Plywood (face 1)
Aluminium (face 2) Plywood (face 2)
Prop. painted steel (face 1)
Plain unrusted steel (face 1)
Prop. painted steel (face 2)
Plain unrusted steel (face 2)
Plywood (face 1)
Aluminium (face 1)
Plywood (face 2)
Aluminium (face 2)
Coefficient of static friction
m
0 kg
0.6
0.7
0.5
0.7
0.3
0.3
0.4
0.3
25 kg
0.6
0.6
0.5
0.6
0.3
0.3
0.4
0.3
Prior to the commencement of testing it was anticipated that if loading had any effect on the
value of coefficient of friction it would be to cause an increase, and this was in fact generally
found to be the case. In certain cases, however, the measured friction value actually reduced
with an increase in load. To check whether the reduction in friction was due to surface
changes, such as polishing, the zero load test was repeated each time this occurred. Member
combinations affected by this behaviour and the corresponding results are summarised in
Table 9.
Table 9 Tests where measured coefficient of friction reduced with increasing load
Upper Member
Lower Member
Aluminium
Plain rusted steel
Coefficient of static
friction, m
0 kg 25 kg 0 kg
0.6
0.5
0.5
Plywood (used
film faced)
Plain rusted steel
Plain rusted steel
0.6
0.4
0.4
Galvanised steel
0.4
0.3
0.3
Aluminium
Galvanised steel
0.4
0.2
0.3
Galvanised steel
Aluminium
0.4
0.2
0.3
Plywood (combi
ply faced)
Plywood (film
faced Finnish)
Aluminium
Aluminium
0.3
0.2
0.3
Softwood perp.
0.4
0.2
0.2
Hardwood par.
0.5
0.4
0.5
Aluminium
Hardwood perp.
0.5
0.3
0.4
Prop. painted
steel
Plywood (good
one side)
Prop. timber
(new)
Plywood (film
faced quality)
0.6
0.5
0.6
0.3
0.2
0.3
16
Comment
Returned to higher value on retesting at zero load
Reduced from initial value to loaded
value on re-testing at zero load
Reduced from initial value to loaded
value on re-testing at zero load
Increased but did not reach initial
value on re-testing at zero load
Increased but did not reach initial
value on re-testing at zero load
Returned to higher value on retesting at zero load
Reduced from initial value to loaded
value on re-testing at zero load
Returned to higher value on retesting at zero load
Increased but did not reach initial
value on re-testing at zero load
Reduced from initial value to loaded
value on re-testing at zero load
Returned almost to initial values on
re-testing
One possible explanation for this behaviour is the existence of a cohesive element of sliding
resistance, which is only perceptible between certain member combinations. The limiting
frictional force would then be expressed as:
Ff = c + mR [2]
where: R is the
reaction force normal to the surface (N) c is the cohesive reaction force (N) Ff is the limiting value of the frictional force (N) This relationship is illustrated in Figure 3. It is clear from the figure that if the behaviour is as
represented in equation 2, but is assumed to be as represented in equation 1, then an increase
in reaction force from say point A to point B on Figure 3 will result in an apparent reduction
in the friction angle from q2 to q3, whereas the true friction angle remains constant at q1.
Ff
B
A
Ff = c + mR
q1
c
q2
Ff = mR
q3
R
tan q1 = true friction coefficient
tan q2, tan q3 = apparent friction coefficients calculated using F = mR
Figure 3 Friction behaviour with cohesive component
The effect of time on coefficient of friction was investigated by performing a zero load test,
leaving the test set-up for two days then repeating the test. From the data, presented in Table
10, it appears that friction values are not affected by time.
17
Table 10 Investigation of bedding/time effects
Lower Member
Upper Member
Coefficient of static friction,
m
0 kg
25 kg
Plain unrusted steel (face 1)
Prop. painted steel (face 1)
0.6
0.7
Plain unrustedsteel (face 1)
Repeated after 48 hrs
Prop. painted steel (face 1)
Repeated after 48 hrs
0.6
0.7
Aluminium (face 1)
Plywood
0.3
0.3
Aluminium (face 1
Repeated after 48 hrs
Plywood (face 1)
Repeated after 48 hrs
0.3
0.3
For material combinations for which experimental data exist for dry timber, the friction
values obtained in the current research for saturated timber exceeded the corresponding
values for dry timber. One possible explanation for the increase in frictional resistance is that
the surface roughness of saturated wood is greater than that of "dry" wood and that this
hypothesised increase in surface roughness outweighs the lubricating effect of surface
moisture.
For material combinations for which codified data exists, the experimental values obtained in
this research for saturated timber lie between the maximum and minimum values quoted in
the codes, with one exception. In the case of wet softwood lying parallel to wet softwood the
maximum experimental value in this study exceeded the maximum value of the coefficient of
static friction quoted in prEN 12812 (Ref 3).
18
5 COMPARISON OF RESULTS WITH CURRENT
INFORMATION
The existing data are presented in Tables 1 and 2, and the data from the current study in
Table 6a and Table 6b. Where both British and German data already exist, the data from the
current study (Table 6a and Table 6b) lie between the existing maximum and minimum
values (Tables 1 and 2) and are closer to the British values with one exception. In the case of
wet softwood lying parallel to wet softwood the maximum experimental value in this study
exceeded the maximum value of the coefficient of static friction quoted in prEN 12812
(Ref 3) for dry timber. The only cases where there are large discrepancies between data are
where the existing British values appear rather low and correspond to friction angles of zero
or around five degrees; see for example the data for the hardwood/plain steel combination.
Absolute agreement with either set of existing data would not be expected as the coefficient
of static friction is an inherently variable quantity and susceptible to variation in test method
and the surface quality of material used in the test. Unfortunately, it has not been possible
either to determine the quality of the surface finishes of the materials used to obtain the data
reported in the British and German Standards, or to locate details of the test methods.
The observed level of agreement between existing data and that from the current study
implies that the friction values for previously untested material combinations, presented in
this report, can be used with confidence in temporary works calculations. A summary of the
friction values recommended for use as a result of this investigation is presented in Table 11.
The values in bold italics are minimum values of the coefficient of static friction contained
in BS 5975: 1996 (Ref 2).
19
Table 11 – Recommended Friction values
SURFACE 1
Steel
Alum.
Plain
Unrusted
Plain
rusted
Galv.
Plain unrusted
0.3
0.4
Plain rusted
0.4
Galvanised
Timber
Soft wood
Plywood
Hard wood
Concrete
Film
faced
Finnish
Film
faced
quality
Cast
face
Prop.
painted
Prop.
waling
Parallel
Perp
Parallel
Perp
Proprietary
beam
Good
one side
Combi
ply faced
0.3
0.3
0.2
0.3
0.4
0.4
0.5
0.5
0.3
--
--
0.1
0.1
0.4
0.3
0.6
0.3
--
--
0.6
--
0.4
0.3
0.2
0.2
0.2
--
0.3
0.3
0.2
0.4
0.2
0.4
0.5
0.5
0.5
0.4
0.2
--
--
0.1
--
Proprietary painted
0.3
0.6
0.4
0.7
0.4
0.4
0.4
0.4
0.5
0.5
0.4
0.2
0.2
0.1
0.0
Proprietary waling
0.2
0.3
0.2
0.4
0.2
0.4
0.4
0.4
0.3
0.2
0.2
0.2
0.2
0.1
--
0.3
--
0.4
0.4
0.4
0.6
0.5
0.4
0.4
0.4
0.2
0.2
0.3
0.2
0.8
SURFACE 2
Steel
Aluminium
Softwood
Timber
Parallel
Perpendicular
0.4
--
0.5
0.4
0.4
0.5
--
0.4
--
0.3
0.3
0.2
0.2
0.1
0.7
Parallel
0.4
0.6
0.5
0.4
0.4
0.4
0.4
0.4
0.5
0.4
0.3
--
--
0.2
0.5
Perpendicular
0.5
--
0.5
0.5
0.3
0.4
--
0.5
--
0.4
0.3
--
--
0.2
0.7
Proprietary beam
0.5
0.4
0.4
0.5
0.2
0.4
0.3
0.4
0.4
0.5
0.3
--
--
0.1
--
0.3
0.3
0.2
0.4
0.2
0.2
0.3
0.3
0.3
0.3
0.3
0.2
0.2
0.2
0.3
Combi ply faced
--
0.2
--
0.2
0.2
0.2
0.2
--
--
--
0.2
--
--
--
0.3
Film faced Finnish
--
0.2
--
0.2
0.2
0.3
0.2
--
--
--
0.2
--
--
--
0.3
Film faced quality
0.1
0.2
0.1
0.1
0.1
0.2
0.1
0.2
0.2
0.1
0.2
--
--
0.2
0.2
Cast face
0.1
--
--
0.0
--
0.8
0.7
0.5
0.7
--
0.3
0.3
0.3
0.2
0.4
Trowelled face
0.5
0.7
0.2
0.6
0.4
1.1
0.7
0.7
0.6
0.6
0.3
--
--
--
0.4
Granular
0.3
--
--
0.3
--
0.3
0.3
0.3
0.3
--
--
--
--
--
0.4
Hardwood
Good one side
Plywood
Hardened
Concrete
Soil
20
6 CONCLUSIONS 1. The value of coefficient of static friction does not appear to be affected by member
position, i.e. upper or lower. Further testing of member combinations, where initial data
suggested that friction values may be a function of position, did not produce any pattern
indicating that the variation was either due to natural scatter or the testing of different
faces in different positions.
2. Application of load to the upper member generally results in a small increase in friction
value. Subsequent increases in load do not, however, appear to affect the friction
coefficient.
3. The sliding resistance between two materials with contacting surfaces may consist of a
cohesive component in addition to the frictional resistance.
4. Friction values quoted in BS 5975 are similar to the minimum values quoted by DIN4421.
Where friction values have been obtained in this research for material combinations
already quoted in existing standards, the results (with one exception) lie between the
maximum and minimum values of the existing data and tend to be closer to the minimum
values. For use in temporary works the recommended values from this research may be
used as lower bound values (Table 11).
5. The agreement between current minimum values of friction coefficient and those obtained
in the current study suggests that friction values obtained for combinations of materials
not previously tested are acceptable for use as lower bound values of friction coefficient.
6. Conclusions 4 and 5 imply that the use of current minimum values of friction coefficient
does not have adverse safety implications.
21
22
7 RECOMMENDATIONS The amount of scatter observed in a few of the tests which were repeated with each member
in both upper and lower position suggests that more replicates are needed in future testing.
The possibility that sliding resistance consists of a cohesive as well as a frictional component
requires further investigation.
The material combinations tested to date are representative of the head, i.e. soffit, level in
temporary works. Material combinations also need to be tested which represent the various
interfaces at the base level.
23
24
11 ACKNOWLEDGEMENTS
The following companies provided materials for the tests:
Mr T C Page
Kymmene Schaumann (UK) Ltd
Stags End House
Hemel Hempstead
Hertfordshire HP2 6HN
Tel No. 01582 794661
Mr I Fryer
Chief Engineer
RMD - Kwikform Ltd
Stubbers Green Road
Aldridge
Walsall
West Midlands WS9 8BW
Tel No. 01922 743743
Mr C Heathcote
Chief Executive
Peri Ltd
Market Harborough Road
Clifton-upon-Dunsmore
Rugby
Warwickshire CV23 OAN
Tel No. 01788 861600
25
26
12 REFERENCES 1 HEALTH AND SAFETY EXECUTIVE Falsework Design - Comparative
Calculations, File No. 617/DST/1004/1998, Report 300-207-R01, October 1998,
113pp.
2 BRITISH STANDARDS INSTITUTION, BS 5975: 1996: Code of Practice for
Falsework, London, March, 1996, 134pp. ISBN 0 580 24949 2 including AMD
9289 December 1996.
3 BRITISH STANDARDS INSTITUTION, Draft prEN 12812 Falsework Performance requirements and general design, Draft for Public Comment
97/102975DC, London, April 1997, 40pp.
4 DEUTSCHES INTSTITUT FUR NORMUNG, Falsework - Calculation, design
and construction DIN 4421: 1982, Beuth Veriag GmbH, Berlin 30, August 1982,
20pp.
27
28
ABBREVIATIONS
alum.
Aluminium
BS
British Standards Insitutution
CEN
Comite Europeen de Normalisation
DIN
Deutsches Institut fur Normung
galv.
galvanised
HSE
Health and Safety Executive
par.
parallel
perp.
perpendicular
prop.
proprietary
29
30
APPENDIX A
Friction Test Data
31
Upper member: Plain unrusted steel
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.4
0.3
2
0.4
0.3
3
0.3
0.3
Plain rusted steel
1
2
3
Galvanised steel
1
0.3
0.3
2
0.4
0.3
3
0.4
0.3
Proprietary painted steel
1
0.3
0.5
2
0.3
0.3
3
0.3
0.4
Aluminium
1
0.3
0.3
2
0.3
0.2
3
0.3
0.2
Softwood (parallel)
1
0.3
0.4
2
0.3
0.4
3
0.4
0.4
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.4
0.5
2
0.5
0.5
3
0.4
0.5
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.5
0.6
2
0.5
0.6
3
0.5
0.5
Plywood – good one side
1
0.2
0.4
2
0.3
0.4
3
0.3
0.4
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.1
0.1
2
0.1
0.1
3
0.1
0.1
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
0.5
0.5
2
0.6
0.5
3
0.6
0.5
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
32
50 kg
0.3
0.3
0.3
0.0
0.0
0.0
0.4
0.4
0.4
0.2
0.2
0.2
0.5
0.5
0.5
0.4
0.4
0.3
0.1
0.1
0.1
0.0
0.0
0.0
Upper member: Plain rusted steel
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.5
0.4
2
0.5
0.4
3
0.4
0.4
Plain rusted steel
1
0.5
0.5
2
0.4
0.5
3
0.4
0.5
Galvanised steel
1
0.6
0.4
2
0.6
0.4
3
0.5
0.4
Proprietary painted steel
1
0.8
0.6
2
0.6
0.7
3
0.5
0.7
1
0.5
0.4
* Aluminium
2
0.6
0.3
3
0.5
0.4
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.6
2
0.6
0.5
3
0.6
0.6
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
0.7
0.6
2
0.6
0.6
3
0.6
0.5
Proprietary timber beam (new)
1
0.4
0.5
2
0.4
0.5
3
0.5
0.5
Plywood – good one side
1
0.6
0.4
2
0.5
0.4
3
0.7
0.4
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood –film faced Finnish
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood – film faced quality
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
1
0.6
0.4
* Plywood – used phenol faced
2
0.6
0.4
3
0.6
0.4
Hardened concrete (trowelled face)
1
0.8
0.8
2
0.8
0.7
3
0.7
0.8
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
50 kg
Plain unrusted steel
33
0.5
0.5
0.5
0.4
0.4
0.5
Upper member: Galvanised steel
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.2
0.3
2
0.3
0.2
3
0.3
0.3
1
0.4
0.3
* Plain rusted steel
2
0.4
0.2
3
0.4
0.2
Galvanised steel
1
0.3
0.3
2
0.3
0.2
3
0.3
0.2
Proprietary painted steel
1
0.4
0.3
2
0.4
0.4
3
0.3
0.4
1
0.4
0.2
* Aluminium
2
0.3
0.1
3
0.4
0.2
Softwood (parallel)
1
0.5
0.5
2
0.4
0.5
3
0.4
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.4
2
0.5
0.5
3
0.5
0.5
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.4
0.6
2
0.4
0.5
3
0.5
0.5
Plywood – good one side
1
0.3
0.2
2
0.2
0.2
3
0.2
0.2
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.2
0.1
2
0.2
0.1
3
0.2
0.1
Plywood – used phenol faced
1
0.3
0.3
2
0.3
0.4
3
0.3
0.3
Hardened concrete (trowelled face)
1
0.4
0.3
2
0.3
0.2
3
0.3
0.2
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
50 kg
Plain unrusted steel
34
0.3
0.3
0.3
0.3
0.4
0.3
Upper member: Proprietary painted steel
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.5
0.6
2
0.5
0.6
3
0.5
0.7
Plain rusted steel
1
2
3
Galvanised steel
1
0.5
0.5
2
0.5
0.5
3
0.6
0.5
Proprietary painted steel
1
0.8
0.7
2
0.8
0.7
3
0.7
0.7
Aluminium
1
0.5
0.5
2
0.5
0.4
3
0.5
0.4
Softwood (parallel)
1
0.5
0.5
2
0.5
0.5
3
0.5
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.7
2
0.6
0.6
3
0.5
0.6
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.5
0.6
2
0.5
0.6
3
0.5
0.7
Plywood – good one side
1
0.4
0.4
2
0.4
0.5
3
0.4
0.4
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood –film faced Finnish
1
0.2
0.2
2
0.2
0.3
3
0.2
0.2
Plywood – film faced quality
1
0.1
0.2
2
0.1
0.2
3
0.2
0.2
Plywood – used phenol faced
1
0.3
0.4
2
0.3
0.4
3
0.3
0.4
Hardened concrete (trowelled face)
1
0.6
0.7
2
0.6
0.7
3
0.6
0.6
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
35
50 kg
0.6
0.6
0.6
0.5
0.5
0.4
0.6
0.7
0.6
0.5
0.6
0.6
0.4
0.4
0.4
0.2
0.3
0.3
Upper member: Aluminium
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.4
0.5
2
0.3
0.3
3
0.4
0.3
Plain rusted steel
1
2
3
1
0.4
0.2
* Galvanised steel
2
0.4
0.2
3
0.3
0.2
Proprietary painted steel
1
0.5
0.3
2
0.4
0.4
3
0.4
0.4
Aluminium
1
0.2
0.4
2
0.3
0.4
3
0.2
0.4
Softwood (parallel)
1
0.4
0.4
2
0.3
0.5
3
0.4
0.4
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.4
0.4
2
0.4
0.4
3
0.4
0.4
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.2
0.4
2
0.2
0.4
3
0.2
0.4
Plywood – good one side
1
0.5
0.3
2
0.4
0.3
3
0.5
0.3
Wet plywood – good one side
1
2
3
1
0.2
0.2
* Plywood – combi ply faced
2
0.3
0.2
3
0.3
0.2
Plywood –film faced Finnish
1
0.4
0.2
2
0.4
0.2
3
0.4
0.2
Plywood – film faced quality
1
0.1
0.1
2
0.1
0.1
3
0.1
0.1
Plywood – used phenol faced
1
0.3
0.3
2
0.3
0.3
3
0.3
0.3
Hardened concrete (trowelled face)
1
0.4
0.6
2
0.3
0.6
3
0.4
0.7
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
36
50 kg
0.3
0.3
0.3
0.3
0.2
0.2
0.3
0.3
0.3
Upper member: Softwood (parallel)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.5
0.5
2
0.6
0.6
3
0.5
0.6
Plain rusted steel
1
2
3
Galvanised steel
1
0.4
0.5
2
0.4
0.5
3
0.3
0.5
Proprietary painted steel
1
0.4
0.6
2
0.4
0.5
3
0.5
0.5
Aluminium
1
0.4
0.4
2
0.4
0.4
3
0.4
0.4
Softwood (parallel)
1
0.8
0.6
2
0.7
0.6
3
0.6
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.4
0.6
2
0.5
0.5
3
0.5
0.5
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.5
0.6
2
0.4
0.5
3
0.4
0.4
Plywood – good one side
1
0.3
0.2
2
0.3
0.2
3
0.3
0.2
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
0.3
0.2
2
0.3
0.2
3
0.3
0.3
Plywood –film faced Finnish
1
0.3
0.2
2
0.3
0.3
3
0.3
0.3
Plywood – film faced quality
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood – used phenol faced
1
0.5
0.5
2
0.6
0.5
3
0.6
0.5
Hardened concrete (trowelled face)
1
1.0
1.0
2
1.1
1.2
3
1.0
1.1
Hardened concrete (cast face)
1
0.8
0.8
2
0.8
0.8
3
0.7
0.8
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
37
50 kg
Upper member: Softwood (perpendicular)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.4
0.4
2
0.4
0.4
3
0.5
0.4
Plain rusted steel
1
2
3
Galvanised steel
1
0.5
0.5
2
0.5
0.5
3
0.6
0.5
Proprietary painted steel
1
0.4
0.6
2
0.4
0.6
3
0.4
0.7
Aluminium
1
0.5
0.4
2
0.5
0.4
3
0.5
0.4
Softwood (parallel)
1
0.5
0.6
2
0.6
0.6
3
0.5
0.6
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.4
0.5
2
0.4
0.4
3
0.4
0.4
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.4
0.4
2
0.5
0.3
3
0.4
0.3
Plywood – good one side
1
0.3
0.3
2
0.3
0.3
3
0.4
0.3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
1
0.4
0.2
* Plywood –film faced Finnish
2
0.3
0.2
3
0.4
0.2
Plywood – film faced quality
1
0.1
0.2
2
0.1
0.2
3
0.1
0.2
Plywood – used phenol faced
1
0.3
0.3
2
0.3
0.3
3
0.3
0.4
Hardened concrete (trowelled face)
1
0.8
0.9
2
0.7
0.8
3
0.7
0.8
Hardened concrete (cast face)
1
0.7
0.7
2
0.7
0.7
3
0.7
0.7
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
50 kg
Plain unrusted steel
38
0.2
0.2
0.2
Upper member: Wet softwood (parallel)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.7
2
0.7
3
0.7
Plain rusted steel
1
0.8
2
0.8
3
0.8
Galvanised steel
1
2
3
Proprietary painted steel
1
0.7
2
0.8
3
0.7
Aluminium
1
0.6
2
0.6
3
0.6
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
1.0
2
0.9
3
1.1
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
0.9
2
0.9
3
0.8
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
39
50 kg
Upper member: Wet softwood (perpendicular)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
2
3
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
2
3
Aluminium
1
2
3
Softwood (parallel)
1
0.9
2
0.9
3
0.9
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
40
50 kg
Upper member: Hardwood (parallel)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.5
0.5
2
0.5
0.5
3
0.5
0.5
Plain rusted steel
1
2
3
Galvanised steel
1
0.5
0.6
2
0.5
0.5
3
0.4
0.6
Proprietary painted steel
1
0.4
0.3
2
0.5
0.4
3
0.5
0.5
1
0.6
0.4
* Aluminium
2
0.5
0.4
3
0.5
0.4
Softwood (parallel)
1
0.5
0.4
2
0.4
0.4
3
0.5
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.5
2
0.5
0.4
3
0.5
0.5
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.5
0.4
2
0.4
0.4
3
0.4
0.4
Plywood – good one side
1
0.3
0.3
2
0.3
0.3
3
0.3
0.3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood – used phenol faced
1
0.0
0.0
2
0.0
0.0
3
0.0
0.0
Hardened concrete (trowelled face)
1
0.7
0.7
2
0.6
0.7
3
0.7
0.7
Hardened concrete (cast face)
1
0.5
0.6
2
0.5
0.6
3
0.5
0.7
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
50 kg
Plain unrusted steel
41
0.5
0.5
0.5
Upper member: Hardwood (perpendicular)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.5
0.5
2
0.5
0.5
3
0.5
0.5
Plain rusted steel
1
2
3
Galvanised steel
1
0.5
0.5
2
0.5
0.5
3
0.5
0.5
Proprietary painted steel
1
0.5
0.6
2
0.5
0.6
3
0.5
0.6
1
0.6
0.3
* Aluminium
2
0.5
0.3
3
0.6
0.3
Softwood (parallel)
1
0.4
0.5
2
0.5
0.5
3
0.4
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.5
2
0.5
0.5
3
0.6
0.5
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.3
0.4
2
0.4
0.4
3
0.4
0.4
Plywood – good one side
1
0.5
0.4
2
0.4
0.3
3
0.4
0.3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
0.7
0.8
2
0.6
0.8
3
0.6
0.7
Hardened concrete (cast face)
1
0.7
0.7
2
0.7
0.7
3
0.7
0.6
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
50 kg
Plain unrusted steel
42
0.4
0.4
0.4
Upper member: Wet hardwood (parallel)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.7
2
0.6
3
0.6
Plain rusted steel
1
0.8
2
0.8
3
0.8
Galvanised steel
1
2
3
Proprietary painted steel
1
0.9
2
0.9
3
0.9
Aluminium
1
0.7
2
0.7
3
0.6
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
0.8
2
0.8
3
0.8
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
0.8
2
0.8
3
0.8
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
0.9
2
0.8
3
0.8
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
43
50 kg
Upper member: Wet hardwood (perpendicular)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
2
3
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
2
3
Aluminium
1
2
3
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
0.7
2
1.0
3
0.9
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
0.9
2
0.8
3
0.8
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
0.7
2
0.7
3
0.8
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
44
50 kg
Upper member: Proprietary timber beam (old)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
2
3
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
2
3
Aluminium
1
2
3
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
0.4
0.4
2
0.4
0.3
3
0.4
0.3
Hardened concrete (trowelled face)
1
0.8
0.8
2
0.8
0.8
3
0.8
0.8
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
45
50 kg
Upper member: Proprietary timber beam (new)
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.6
0.5
2
0.5
0.6
3
0.5
0.5
Plain rusted steel
1
2
3
Galvanised steel
1
0.4
0.4
2
0.4
0.4
3
0.4
0.4
1
0.6
0.5
* Proprietary painted steel
2
0.6
0.5
3
0.6
0.5
Aluminium
1
0.5
0.5
2
0.5
0.4
3
0.5
0.5
Softwood (parallel)
1
0.5
0.5
2
0.6
0.5
3
0.6
0.5
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.5
0.4
2
0.5
0.4
3
0.5
0.4
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.6
0.5
2
0.5
0.4
3
0.5
0.5
Plywood – good one side
1
0.4
0.4
2
0.3
0.4
3
0.3
0.4
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.2
0.2
2
0.1
0.2
3
0.1
0.2
Plywood – used phenol faced
1
0.4
0.4
2
0.4
0.4
3
0.5
0.4
Hardened concrete (trowelled face)
1
0.6
0.7
2
0.7
0.6
3
0.6
0.7
Hardened concrete (cast face)
1
2
3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
46
50 kg
0.5
0.5
0.5
0.0
0.0
0.0
0.5
0.5
0.5
0.5
0.4
0.5
0.4
0.4
0.5
0.4
0.3
0.3
0.2
0.2
0.2
Upper member: Plywood – good one side
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.3
0.4
2
0.3
0.4
3
0.3
0.3
Plain rusted steel
1
0.4
0.4
2
0.3
0.4
3
0.3
0.4
Galvanised steel
1
0.2
0.2
2
0.2
0.3
3
0.2
0.2
Proprietary painted steel
1
0.4
0.5
2
0.5
0.5
3
0.5
0.5
Aluminium
1
0.2
0.3
2
0.2
0.3
3
0.2
0.3
Softwood (parallel)
1
0.3
0.3
2
0.4
0.3
3
0.3
0.3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.3
0.4
2
0.3
0.3
3
0.3
0.3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.3
0.3
2
0.3
0.3
3
0.3
0.3
Plywood – good one side
1
0.5
0.3
2
0.5
0.3
3
0.5
0.3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
0.3
0.2
2
0.3
0.2
3
0.3
0.2
Plywood –film faced Finnish
1
0.3
0.2
2
0.3
0.2
3
0.3
0.2
Plywood – film faced quality
1
0.2
0.2
2
0.1
0.2
3
0.2
0.2
Plywood – used phenol faced
1
0.4
0.4
2
0.3
0.3
3
0.3
0.3
Hardened concrete (trowelled face)
1
0.3
0.4
2
0.4
0.3
3
0.4
0.3
Hardened concrete (cast face)
1
0.4
0.3
2
0.4
0.3
3
0.4
0.3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
47
50 kg
0.3
0.3
0.3
0.4
0.5
0.4
0.3
0.3
0.2
0.3
0.3
0.3
0.4
0.4
0.3
0.2
0.2
0.2
Upper member: Wet plywood – good one side
Lower Member
Test
Coefficient of friction
0 kg
Plain unrusted steel
25 kg
1
0.5
2
0.6
3
0.6
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
0.7
2
0.7
3
0.7
Aluminium
1
2
3
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
0.7
2
0.6
3
0.7
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
48
50 kg
Upper member: Plywood – combi ply faced
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
2
3
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
2
3
Aluminium
1
2
3
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
0.3
0.2
2
0.3
0.3
3
0.3
0.3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
49
50 kg
Upper member: Plywood – film faced Finnish
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
2
3
Plain rusted steel
1
2
3
Galvanised steel
1
2
3
Proprietary painted steel
1
2
3
Aluminium
1
2
3
Softwood (parallel)
1
2
3
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
2
3
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
2
3
Plywood – good one side
1
2
3
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
2
3
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
0.3
0.3
2
0.3
0.2
3
0.3
0.3
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
50
50 kg
Upper member: Plywood – film faced quality
Lower Member
Test
Coefficient of friction
0 kg
25 kg
1
0.2
0.1
2
0.2
0.1
3
0.2
0.1
Plain rusted steel
1
2
3
Galvanised steel
1
0.1
0.1
2
0.1
0.1
3
0.1
0.1
Proprietary painted steel
1
0.2
0.3
2
0.2
0.3
3
0.2
0.3
Aluminium
1
0.2
0.1
2
0.2
0.1
3
0.2
0.1
Softwood (parallel)
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Wet softwood (parallel)
1
2
3
Hardwood (parallel)
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
Wet hardwood (parallel)
1
2
3
Proprietary timber beam (old)
1
2
3
Proprietary timber beam (new)
1
0.2
0.2
2
0.2
0.2
3
0.2
0.2
1
0.3
0.2
* Plywood – good one side
2
0.3
0.2
3
0.3
0.2
Wet plywood – good one side
1
2
3
Plywood – combi ply faced
1
2
3
Plywood –film faced Finnish
1
2
3
Plywood – film faced quality
1
0.2
0.2
2
0.2
0.1
3
0.2
0.1
Plywood – used phenol faced
1
2
3
Hardened concrete (trowelled face)
1
2
3
Hardened concrete (cast face)
1
0.2
0.2
2
0.3
0.2
3
0.2
0.2
Note: * indicates that the third set of tests was a repeat of the zero load test and not a 50 kg test.
Plain unrusted steel
51
50 kg
0.1
0.1
0.2
0.2
0.3
0.3
0.1
0.1
0.1
0.3
0.3
0.2
0.0
0.0
0.0
Effect of Member Position
Lower Member
Upper Member
Test
Plain unrusted steel
(face 1)
Prop. painted steel
(face 1)
Prop. painted steel
(face 1)
Plain unrusted steel
(face 1)
Plain unrusted steel
(face 2)
Prop. painted steel
(face 2)
Prop. painted steel
(face 2)
Plain unrusted steel
(face 2)
Aluminium (face 1)
Plywood (face 1)
Plywood (face 1)
Aluminium (face 1)
Aluminium (face 2)
Plywood (face 2)
Plywood (face 2)
Aluminium (face 2)
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
Coefficient of friction
0kg
25kg
0.5
0.5
0.6
0.6
0.6
0.6
0.7
0.6
0.7
0.6
0.7
0.6
0.4
0.4
0.5
0.5
0.6
0.5
0.7
0.6
0.7
0.6
0.7
0.6
0.3
0.2
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.4
0.2
0.4
0.4
0.4
0.3
0.4
0.4
0.4
0.3
0.3
0.4
0.3
0.4
Investigation of bedding/time effects
Lower Member
Upper Member
Test
Plain unrusted steel
(face 1)
Prop. painted steel (face 1)
Plain unrusted steel
(face 1)
Repeated after 48 hrs
Aluminium (face 1)
Prop. painted steel (face 1)
Repeated after 48 hrs
Aluminium (face 1)
Repeated after 48 hrs
Plywood (face 1)
Repeated after 48 hrs
1
2
3
1
2
3
1
2
3
1
2
3
Plywood (face 1)
52
Coefficient of friction
0kg
25kg
0.6
0.7
0.6
0.7
0.7
0.7
0.6
0.7
0.6
0.7
0.7
0.7
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
0.3
APPENDIX B
Saturation Test Data
53
Time (days)
0
1
5
14
19
Specimen
Softwood 1
Softwood 2
Plywood
Hardwood 1
Hardwood 2
Softwood 1
Softwood 2
Plywood
Hardwood 1
Hardwood 2
Softwood 1
Softwood 2
Plywood
Hardwood 1
Hardwood 2
Softwood 1
Softwood 2
Plywood
Hardwood 1
Hardwood 2
Softwood 1
Softwood 2
Plywood
Hardwood 1
Hardwood 2
Reading 1
6
6
0
12
14
25
25
28
25
28
26
26
28
26
26
26
28
28
28
28
26
26
26
26
28
Moisture Content (% water)
Reading 2 Reading 3
Average
6
6
6.0
6
6
6.0
0
0
0.0
14
12
12.7
14
14
14.0
25
23
24.3
23
25
24.3
28
28
28.0
26
26
25.7
26
28
27.3
26
26
26.0
25
26
25.7
28
26
27.3
28
28
27.3
26
28
26.7
26
26
26.0
26
26
26.7
28
26
27.3
28
26
27.3
28
28
28.0
26
26
26.0
26
26
26.0
26
26
26.0
28
26
26.7
26
26
26.7
Printed and published by the Health and Safety Executive
C1.25
02/03
ISBN 0-7176-2613-X
RR 071
£15.00
9 780717
626137