1、BS 7941-1:2006Methods for measuring the skid resistance of pavement surfaces Part 1: Sideway-force coefficient routine investigation machineICS 93.080.20NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDPublishing and copyright informationThe BSI copyright notice
2、displayed in this document indicates when the document was last issued. BSI 2006ISBN 0 580 48997 3The following BSI references relate to the work on this standard:Committee reference B/510/5Publication historyFirst published, October 1999Second (present) edition, November 2006Amendments issued since
3、 publicationAmd. no. Date Text affectedBS 7941-1:2006 BSI 2006 iBS 7941-1:2006ContentsForeword iii1 Scope 12 Normative references 13 Terms and definitions 14 Safety 25 Principle 36 Test equipment 37 Calibration 58 Test procedure 79 Test report 8AnnexesAnnex A (normative) Dynamic calibration check 9A
4、nnex B (normative) Distance calibration check 10Annex C (informative) Report format 11Annex D (informative) (informative) Precision of data 12Bibliography 13List of tablesTable 1 Static calibration 6Summary of pagesThis document comprises a front cover, an inside front cover, pages i to iv, pages 1
5、to 13 and a back cover.BS 7941-1:2006ii BSI 2006 This page deliberately left blank BSI 2006 iiiBS 7941-1:2006ForewordPublishing informationThis British Standard was published by BSI. It was prepared by Subcommittee B/510/5, Surface characteristics, under the authority of Technical Committee B/510, R
6、oad materials. A list of organizations represented on this committee can be obtained on request to its secretary.SupersessionThis part of BS 7941 supersedes BS 7941-1:1999 which is declared obsolescent.Information about this documentThis new edition represents a full revision of the standard, and in
7、troduces 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 document, although not in the princi
8、ples 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 subclause to cover the new vertical
9、load calibration, which has two procedures, one for full calibration and the other for a daily spot-check. Relationship with other publicationsThe changes to the hardware associated with the introduction of DVLM were implemented across the whole of the UK fleet in early 2004. The changes in this rev
10、ision 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 to the 1999 edition, upgrade their
11、 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 GripTester braked wheel fixed slip devicePre
12、sentational conventionsThe 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 in smaller italic type, and does not c
13、onstitute a normative element.BS 7941-1:2006iv BSI 2006Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal o
14、bligations. BSI 2006 1BS 7941-1:20061 ScopeThis 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 wet-road skid resistance properties of a bound
15、 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 referencesThe following referenced documents are indispensable for the application of this document
16、. 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 resilience3 Terms and definitionsFor the purposes of this Bri
17、tish Standard the following terms and definitions apply.3.1 skid resistanceproperty of a trafficked surface that limits relative movement between the surface and the part of a vehicle tyre in contact with the surface3.2 wet-road skid resistanceproperty of a trafficked surface that limits relative mo
18、vement between the surface and the part of a vehicle tyre in contact with the surface, when lubricated with a controlled film of waterNOTE 1 Factors that contribute to skid resistance include the tyre pressure, contact area, tread pattern, and rubber composition; the alignment, texture, surface cont
19、amination, 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.3.3 bound surfacetop layer or surface course of a roadNOTE Aggregates are commonly secured in place by bitumen or
20、 cement.3.4 sideway-force coefficient (SFC)ratio between the vertical force and sideway-force normal to a test wheel maintained in a slipping conditionNOTE The controlled slipping condition is achieved by mounting a freely rotating test wheel with its vertical plane at an angle to the longitudinal p
21、lane 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.3.5 subsectionlength of road for which SCRIM records one SRNOTE A subsection can be 5 m, 10 m or 20 m.BS 7941
22、-1:20062 BSI 20063.6 test sectionlength of road between defined points (e.g. location references, specific features, or measured distances)3.7 test lengthnumber of test sections over which a continuous sequence of measurements is made3.8 SCRIM reading (SR)measurement recorded by SCRIM for a single s
23、ubsectionNOTE A SCRIM reading is expressed as a positive integer equalto 100 the SFC.3.9 corrected dataSCRIM readings altered to represent standardized conditionsNOTE Corrected data should be prefixed “corrected” and an indication given of the type of correction (e.g. “speed-corrected SR”).3.10 SCRI
24、M coefficient (SC)corrected data multiplied by the index of SFC (see 3.11) applicable to the SCRIM during the testNOTE SCRIM coefficients are expressed as decimal fractions to two places.3.11 index of SFCratio (expressed as a percentage) of values of SFC obtained from a current calibrated item of te
25、st 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 specificationNOTE The present index of SFC is 78% and is valid for all UK SCRIM machines in current use.3.12 theoretical water film thicknesstheoretic
26、al thickness of a water film between a measuring tyre and a test surface, assuming the surface has zero texture depth4SafetyNOTE 1 When measuring skid resistance on trafficked roads the SCRIM may operate at speeds different to normal road speeds and as a result may create a hazard to other road user
27、s.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 water freezing on the road. BSI 2006 3BS 7941-1:20065 PrincipleA freely rotating w
28、heel 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 vertical load. A controlled flow of water wets the road surface immediately in front of
29、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 the surface and measurement of this sideways component gives the SR.The SCRIM readi
30、ng is affected by the speed of the test vehicle. Testing should be carried out at a specified speed.6 Test equipment6.1 SCRIM test equipmentThe SCRIM test equipment shall include the following features: a) test wheel assembly; b) water supply and flow control mechanism; c) electronic recorder and me
31、asurement 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 number of different vehicle chassis and functions independently of vehicle choice.6.2
32、 Test wheel assemblyMount 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 shall be free to move vertically when the test wheel is in contact with the surface
33、 (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 measure the horizontal load, an electrical load-cell to measure the vertical load and a
34、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 +1.0p0.5) to the line of the chassis. NOTE This angle is the “slip angle”.A mechanism shall be provided for raising and lo
35、wering 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.ukBS 7941-1:20064 BSI 20066.3 Test tyreThe test tyre shall be tubed, pneumatic, natural rubber, (3.
36、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 at least 2 km with a new SCRIM test tyre before results are recorded. Discard the test tyre
37、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 years old.6.4 Water supply and flow controlThe pattern and flow of water shall be controlle
38、d 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 testing, a separate valve shall be provided that turns on the water supply before the tyre touches
39、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 jet of water strikes the level surface shall be (400 50) mm in front of the centre line of the t
40、est 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.The water shall be free from salt, emulsified oils or suspended solids. The theoretical water
41、 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 vary with the level of water in the tank. On a textured road surface, water drains into the texture
42、 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 the theoretical water film thickness can be achieved at 50 km/h. Tests have shown that, for typic
43、al 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 is 0.3 mm.6.5 Measurement control systemThe measurement control system shall enable the operato
44、r 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 after the wheel is raised. BSI 2006 5BS 7941-1:20066.6 Electronic recorderAn electronic recorder
45、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 travelled from a predetermined reference point. The recorder shall be capable of accurately recording
46、 automatic or manual input reference points.7Calibration7.1 Static calibration of horizontal load measurementStatic calibration of the horizontal load measurement shall be carried out using the “rolling trolley” principle, not more than 24 h before commencement of measurements. Lower the test wheel
47、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 trolley so that it is then transmitted directly to the test tyre along the line of the test wheel axle.
48、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 conforms to this principle is normally supplied by the SCRIM manufacturer. The calibration equipment an
49、d 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 during the calibration process. Refer to the manufacturers instructions for any necessary settings
