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
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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
