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1、BS 7941-1:2006 Methods for measuring the skid resistance of pavement surfaces Part 1: Sideway-force coefficient routine investigation machine ICS 93.080.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BRITISH STANDARD Publishing and copyright information The BSI copyright n
2、otice displayed in this document indicates when the document was last issued. BSI 2006 ISBN 0 580 48997 3 The following BSI references relate to the work on this standard: Committee reference B/510/5 Publication history First published, October 1999 Second (present) edition, November 2006 Amendments
3、 issued since publication Amd. no.DateText affected BS 7941-1:2006 BSI 2006i BS 7941-1:2006 Contents Foreword iii 1Scope 1 2Normative references 1 3Terms and definitions 1 4Safety 2 5Principle 3 6Test equipment 3 7Calibration 5 8Test procedure 7 9Test report 8 Annexes Annex A (normative) Dynamic cal
4、ibration check 9 Annex B (normative) Distance calibration check 10 Annex C (informative) Report format 11 Annex D (informative) (informative) Precision of data 12 Bibliography 13 List of tables Table 1 Static calibration 6 Summary of pages This document comprises a front cover, an inside front cover
5、, pages i to iv, pages 1 to 13 and a back cover. BS 7941-1:2006 ii BSI 2006This page deliberately left blank BSI 2006iii BS 7941-1:2006 Foreword Publishing information This British Standard was published by BSI. It was prepared by Subcommittee B/510/5, Surface characteristics, under the authority of
6、 Technical Committee B/510, Road materials. A list of organizations represented on this committee can be obtained on request to its secretary. Supersession This part of BS 7941 supersedes BS 7941-1:1999 which is declared obsolescent. Information about this document This new edition represents a full
7、 revision of the standard, and introduces the following principal changes. Corrects typographical errors in the 1999 edition. Takes account of changes that have introduced dynamic vertical load measurement (DVLM) to all UK SCRIMs. Changes the way in which calibration processes are covered in the doc
8、ument, although not in the principles involved. The standard now describes the principles of the calibration processes and cites the manufacturers instructions for the detail of how to carry them out. This revision puts this into effect for the existing (horizontal) static calibration and adds a sub
9、clause to cover the new vertical load calibration, which has two procedures, one for full calibration and the other for a daily spot-check. Relationship with other publications The changes to the hardware associated with the introduction of DVLM were implemented across the whole of the UK fleet in e
10、arly 2004. The changes in this revision reflect the new position. However, there may be SCRIM owners elsewhere in the world who refer to this British Standard but who will no longer be able to comply fully because their machines are not fitted with a DVLM system. They will need to continue to refer
11、to the 1999 edition, upgrade their machines or change their operating procedures to take account of the differences. The standard is issued in two parts: Part 1: Sideway-force coefficient routine investigation machine Part 2: Test method for measurement of surface skid resistance using the GripTeste
12、r braked wheel fixed slip device Presentational conventions The provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”. Commentary, explanation and general informative material is presented
13、in smaller italic type, and does not constitute a normative element. BS 7941-1:2006 iv BSI 2006 Contractual and legal considerations This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British S
14、tandard cannot confer immunity from legal obligations. BSI 20061 BS 7941-1:2006 1 Scope This British Standard describes a method for determining the wet-road skid resistance of a surface using the sideway-force coefficient routine investigation machine (SCRIM). The method provides a measure of the w
15、et-road skid resistance properties of a bound surface by measurement of sideway-force coefficient at controlled speed. The method has been developed for use on roads but is also applicable to other paved areas such as airport runways. 2 Normative references The following referenced documents are ind
16、ispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 903-A8:1990, Physical testing of rubber Method of determination of rebound resilience 3
17、Terms and definitions For the purposes of this British Standard the following terms and definitions apply. 3.1skid resistance property of a trafficked surface that limits relative movement between the surface and the part of a vehicle tyre in contact with the surface 3.2wet-road skid resistance prop
18、erty of a trafficked surface that limits relative movement between the surface and the part of a vehicle tyre in contact with the surface, when lubricated with a controlled film of water NOTE 1 Factors that contribute to skid resistance include the tyre pressure, contact area, tread pattern, and rub
19、ber composition; the alignment, texture, surface contamination, and characteristics of the road surface; the vehicle speed; and the weather conditions. NOTE 2 Skid resistance is not a constant value. It varies with time, climate and traffic. 3.3bound surface top layer or surface course of a road NOT
20、E Aggregates are commonly secured in place by bitumen or cement. 3.4sideway-force coefficient (SFC) ratio between the vertical force and sideway-force normal to a test wheel maintained in a slipping condition NOTE The controlled slipping condition is achieved by mounting a freely rotating test wheel
21、 with its vertical plane at an angle to the longitudinal plane of the test vehicle. When the vehicle is in motion, the test wheel slides or slips in the forward direction. SFC values depend upon the type of equipment and the way in which it is used. 3.5subsection length of road for which SCRIM recor
22、ds one SR NOTE A subsection can be 5 m, 10 m or 20 m. BS 7941-1:2006 2 BSI 2006 3.6test section length of road between defined points (e.g. location references, specific features, or measured distances) 3.7test length number of test sections over which a continuous sequence of measurements is made 3
23、.8SCRIM reading (SR) measurement recorded by SCRIM for a single subsection NOTE A SCRIM reading is expressed as a positive integer equal to 100 the SFC. 3.9corrected data SCRIM readings altered to represent standardized conditions NOTE Corrected data should be prefixed “corrected” and an indication
24、given of the type of correction (e.g. “speed-corrected SR”). 3.10SCRIM coefficient (SC) corrected data multiplied by the index of SFC (see 3.11) applicable to the SCRIM during the test NOTE SCRIM coefficients are expressed as decimal fractions to two places. 3.11index of SFC ratio (expressed as a pe
25、rcentage) of values of SFC obtained from a current calibrated item of test equipment to values of SFC obtained from the equipment at TRL during the period 19631972 used to derive information on which to base proposals for specification NOTE The present index of SFC is 78% and is valid for all UK SCR
26、IM machines in current use. 3.12theoretical water film thickness theoretical thickness of a water film between a measuring tyre and a test surface, assuming the surface has zero texture depth 4 Safety NOTE 1 When measuring skid resistance on trafficked roads the SCRIM may operate at speeds different
27、 to normal road speeds and as a result may create a hazard to other road users. Safety measures shall be in place to maintain safe working practice in accordance with current regulations, and to ensure the safety of other road users. NOTE 2 Testing should not be carried out if there is a risk of wat
28、er freezing on the road. BSI 20063 BS 7941-1:2006 5 Principle A freely rotating wheel fitted with a pneumatic, smooth rubber tyre, mounted mid-machine in line with the nearside wheeltrack and angled at 20 to the direction of travel of the vehicle, is applied to the road surface under a known vertica
29、l load. A controlled flow of water wets the road surface immediately in front of the test wheel, so that when the vehicle moves forward, the test wheel slides in the forward direction along the surface. The force generated by the resistance to sliding is related to the wet-road skid resistance of th
30、e surface and measurement of this sideways component gives the SR. The SCRIM reading is affected by the speed of the test vehicle. Testing should be carried out at a specified speed. 6 Test equipment 6.1SCRIM test equipment The SCRIM test equipment shall include the following features: a)test wheel
31、assembly; b)water supply and flow control mechanism; c)electronic recorder and measurement control system. NOTE A machine conforming to the general characteristics of the SCRIM designed by the Transport Research Laboratory1) should be used for the tests. SCRIM test equipment has been built onto a nu
32、mber of different vehicle chassis and functions independently of vehicle choice. 6.2Test wheel assembly Mount the test wheel assembly on a frame within the wheel-base of the vehicle. Attach two vertical shafts to the frame and locate the test wheel assembly in the appropriate wheelpath. The assembly
33、 shall be free to move vertically when the test wheel is in contact with the surface (to minimize the effects of vehicle chassis movements). The test wheel assembly shall comprise a back plate for location on the vertical shafts, a swinging arm, hub, test wheel and tyre, electrical load-cell to meas
34、ure the horizontal load, an electrical load-cell to measure the vertical load and a single damper/spring suspension unit. The mass of the test wheel assembly shall provide a static vertical load of (2.00 0.08) kN. Fix the vertical plane of the test wheel at (20 +1.0 p0.5) to the line of the chassis.
35、 NOTE This angle is the “slip angle”. A mechanism shall be provided for raising and lowering the test wheel assembly to and from the ground. 1) Contact TRL Ltd., Crowthorne House, Nine Mile Ride, Wokingham, Berkshire RG40 3GA United Kingdom. Email: enquiriestrl.co.uk. Website: www.trl.co.uk BS 7941-
36、1:2006 4 BSI 2006 6.3Test tyre The test tyre shall be tubed, pneumatic, natural rubber, (3.00/20) in, smooth treaded. The tyre resilience shall be in the range 40% to 49% as measured by the Lupke test (see BS 903-A8:1990). Inflate the tyre to (350 20) kPa, measured at ambient temperature. Test for a
37、t least 2 km with a new SCRIM test tyre before results are recorded. Discard the test tyre when it loses 6 mm in diameter (3.0 mm tyre wear), or if otherwise damaged. Date stamp all tyres and store vertically in a cool dry environment away from direct sunlight. Do not use a tyre that is more than 2
38、years old. 6.4Water supply and flow control The pattern and flow of water shall be controlled by a manually set control valve and fan shaped nozzle. The manual control valve shall include an indicator that allows the water flow to be adjusted depending on test speed. To prevent accidental dry testin
39、g, a separate valve shall be provided that turns on the water supply before the tyre touches the ground. The valve shall remain open so that water continues to flow until the tyre has completely lost contact with the ground when the test wheel assembly is raised. The point where the centre of the je
40、t of water strikes the level surface shall be (400 50) mm in front of the centre line of the test wheel along the direction of the line of travel, and within 75 mm either side, with the wheel parked on the ground. Set the water control valve to provide the theoretical water film thickness at 50 km/h
41、. The water shall be free from salt, emulsified oils or suspended solids. The theoretical water film thickness for the SCRIM test shall be 0.5 mm at 50 km/h. NOTE SCRIM operates with a nominally constant water flow rate. The theoretical water film thickness varies with vehicle test speed and may var
42、y with the level of water in the tank. On a textured road surface, water drains into the texture and so the actual water film thickness in the tyre contact area during a test is variable. It has been found that if the average flow, measured over the discharge of a full tank is (0.95 0.19) l/s then t
43、he theoretical water film thickness can be achieved at 50 km/h. Tests have shown that, for typical UK road surfaces, this flow rate is acceptable, for speeds from 25 km/h, when the theoretical water film thickness is 0.9 mm, up to a maximum speed of 85 km/h, when the theoretical water film thickness
44、 is 0.3 mm. 6.5Measurement control system The measurement control system shall enable the operator to raise and lower the test wheel and ensure that the water supply valve is opened or closed as required. It shall ensure that water flow commences before the wheel touches the road surface and ceases
45、after the wheel is raised. BSI 20065 BS 7941-1:2006 6.6Electronic recorder An electronic recorder shall be provided, capable of measuring the horizontal load, vertical load and distance travelled. The electronic recorder shall display the speed, SR, and length for the subsection and the distance tra
46、velled from a predetermined reference point. The recorder shall be capable of accurately recording automatic or manual input reference points. 7 Calibration 7.1Static calibration of horizontal load measurement Static calibration of the horizontal load measurement shall be carried out using the “roll
47、ing trolley” principle, not more than 24 h before commencement of measurements. Lower the test wheel on to a trolley that is capable of moving freely on a level surface in the line of the test wheel axle and that has a flange that rests against the test tyre. Apply a known horizontal load to the tro
48、lley so that it is then transmitted directly to the test tyre along the line of the test wheel axle. Apply the load progressively at intervals from 0 kg to 200 kg in 20 kg steps as measured by the calibration load-cell. NOTE 1 This procedure requires purpose-made equipment. Suitable equipment that c
49、onforms to this principle is normally supplied by the SCRIM manufacturer. The calibration equipment and electronic recorder should be operated in accordance with the manufacturers instructions for horizontal load calibrations. NOTE 2 The majority of SCRIM recorders use a linear response curve to determine the horizontal load from the electrical output from the load-cell when the machine is operating normally and automatically correct the load-cell output by storing the response to the known loads applied durin
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