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1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 7941-1:1999 Incorporat
2、ing Amendment No. 1 ICS 93.080.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Methods for measuring the skid resistance of pavement surfaces Part 1: Side-way force coefficient routine investigation machine Licensed Copy: London South Bank University, London South Bank Univ
3、ersity, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI This British Standard, having been prepared under the direction of the Sector Committee for Building and Civil Engineering, was published under the authority of the Standards Committee and comes into effect on 15 October 1999 BSI
4、 12-1999 The following BSI references relate to the work on this standard: Committee reference B/510/5 Draft for comment ISBN 0 580 33028 1 BS 7941-1:1999 Amendments issued since publication Amd. No.DateComments 10783December 1999 Indicated by a sideline Committees responsible for this British Stand
5、ard The preparation of this British Standard was entrusted by the Building and Civil Engineering Sector Policy and Strategy Committee (B/-) to Technical Committee B/510, upon which the following bodies were represented: County Surveyors Society Department of the Environment, Transport and the Region
6、s Represented by the Building Research Establishment Institution of Civil Engineers Quarry Products Association Road Surface Dressing Association Society of Chemical Industry The following bodies were also represented in the drafting of the standard, through subcommittees and panels: BAA Plc Brick D
7、evelopment Association Britpave Department of the Environment, Transport and the Regions Highways Agency Ministry of Defence The BSI copyright notice displayed on some pages of the document indicates when the page concerned was last issued. Sidelining, where it appears in this document, indicates th
8、e most recent changes by amendment on the page concerned. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7941-1:1999 BSI 12-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2R
9、eferences1 3Definitions1 4Safety1 5Principle2 6Test equipment2 7Calibration3 8Test procedure3 9Test report3 Annex A (normative) Dynamic calibration check4 Annex B (normative) Dynamic calibration check4 Annex C (informative) Report format5 Annex D (informative) Precision of data5 Table 1 Static calib
10、ration3 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii BSI 12-1999 BS 7941-1:1999 Foreword This British Standard has been prepared under the direction of the Sector Committee for Building and Civil Engineer
11、ing by Subcommittee B/510/5, Surface characteristics. Part 2 of this British Standard gives a method for measuring surface skid resistance using a braked wheel fixed slip device. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are
12、 responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 5 and a back cover. The BSI copyright notice displayed i
13、n this document indicates when the document was last issued. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 12-19991 BS 7941-1:1999 | 1 Scope This British Standard describes a method for determining the we
14、t-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 surface by measurement of sideway-force coefficient at controlled speed. The method has been developed fo
15、r use on roads but is also applicable to other paved areas such as airport runways. 2 References The following normative documents contain provisions that, through reference in this text, constitute provisions of this British Standard. For dated references, subsequent amendments to, or revisions of,
16、 any of these publications do not apply. For undated references, the latest edition of the publication referred to applies. BS 903-A8:1990, Physical testing of rubber Method of determination of rebound resilience. 3 Definitions 3.1 skid resistance property of a trafficked surface that limits relativ
17、e movement between the surface and the part of a vehicle tyre in contact with the surface 3.2 wet road skid 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, when lubricated with a controlled film
18、 of water NOTE 1Factors that contribute to skid resistance include the tyre pressure, contact area, tread pattern, and rubber composition; the alignment, texture, surface contamination, and characteristics of the road surface; the vehicle speed; and the weather conditions. NOTE 2Skid resistance is n
19、ot a constant value. It varies with time, climate and traffic. 3.3 bound surface top layer or wearing course of a road with the aggregates secured permanently in place NOTEAggregates are commonly secured in place by bitumen or cement. 3.4 sideway-force coefficient (SFC) ratio between the vertical fo
20、rce and sideway-force normal to a test wheel maintained in a controlled slipping condition NOTEThe controlled slipping condition is achieved by mounting a freely rotating test wheel with its vertical plane at an angle to the longitudinal plane of the test vehicle. When the vehicle is in motion, the
21、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 subsection length of road for which SCRIM records one SR NOTEA subsection can be 5 m, 10 m or 20 m. 3.6 test section length of road between defined points (e.g. loca
22、tion references, specific features, or measured distances) 3.7 test length number of test sections over which a continuous sequence of measurements is made 3.8 SCRIM reading (SR) measurement recorded by SCRIM for a single subsection NOTEA SCRIM reading is expressed as a positive integer equal to 100
23、 3 the SFC. 3.9 corrected data SCRIM readings altered to represent standardized conditions NOTECorrected data should be prefixed corrected and an indication given of the type of correction (e.g. speed-corrected SR). 3.10 SCRIM coefficient (SC) corrected data multiplied by the index of SFC (see 3.12)
24、 applicable to the SCRIM during the test NOTESCRIM coefficients are expressed as decimal fractions to two places. 3.11 index of SFC ratio (expressed as a percentage) of values of SFC obtained from a current calibrated item of test equipment to values of SFC obtained from the equipment at TRL during
25、the period 1963-1972 used to derive information on which to base proposals for specification NOTEThe present index of SFC is 78 % and is valid for all UK SCRIM machines in current use. 3.12 theoretical water film thickness theoretical thickness of a water film between a measuring tyre and a test sur
26、face, assuming the surface has zero texture depth 4 Safety NOTEWhen 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 users. Safety measures shall be in place to maintain safe working practi
27、ce in accordance with current regulations, and to ensure the safety of other road users. NOTETesting should not be carried out if there is a risk of water freezing on the road. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled
28、 Copy, (c) BSI 2 BSI 12-1999 BS 7941-1:1999 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 208 to the direction of travel of the vehicle, is applied to the road surface under a known vertical loa
29、d. 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 the sur
30、face 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 6.1 SCRIM test equipment The SCRIM test equipment shall include the following features: a) test wheel ass
31、embly; b) water supply and flow control mechanism; c) electronic recorder and measurement control system. NOTEA machine conforming to the general characteristics of the SCRIM designed by the Transport Research Laboratory should be used for the tests. SCRIM test equipment has been built onto a number
32、 of different vehicle chassis and functions independently of vehicle choice. 6.2 Test 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 sh
33、all 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, and singl
34、e damper/spring suspension unit. The mass of the test wheel assembly shall provide a static vertical load of (2002) N. Fix the vertical plane of the test wheel at to the line of the chassis.(20)8 20.5 +1.0 NOTEThis angle is the slip angle. A mechanism shall be provided for raising and lowering the t
35、est wheel assembly to and from the ground. 6.3 Test 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 (3.50.2) kg/cm2, measured at
36、ambient temperature. Test for at 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
37、use a tyre that is more than 2 years old. 6.4 Water 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.
38、To prevent accidental dry testing, 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
39、point where the centre of the jet of water strikes the level surface shall be (40050) mm in front of the centre line of the test wheel along the direction of the line of travel, and within75 mm either side, with the wheel parked on the ground. Set the water control valve to provide the theoretical w
40、ater film thickness at 50 km/h. The water shall be free from salt, emulsified oils or suspended solids. The theoretical water film thickness for the SCRIM test shall be 2 mm. NOTEFor testing at speeds up to 50 km/h, if the average water flow, measured over the discharge of a full tank, is (0.950.19)
41、 l/s, then the theoretical water film thickness can be achieved. If higher speed testing (55 to 65) km/h is undertaken, the average water flow should be (1.200.24) l/s. 6.5 Measurement control system The measurement control system shall enable the operator to raise and lower the test wheel and ensur
42、e 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. 6.6 Electronic recorder An electronic recorder shall be provided, able to measure the sideways force and distance t
43、ravelled. 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 able to accurately record automatic or manual input reference points. Licensed Copy: London South Bank University, Londo
44、n South Bank University, Fri Dec 08 14:55:06 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 12-19993 BS 7941-1:1999 7 Calibration 7.1 Static calibration Static calibration shall be carried out using a rolling trolley calibration rig, in accordance with the manufacturers instructions, not more than 2
45、4 h before commencement of measurements. Before carrying out a static calibration, check that the the test wheel assembly moves freely by lowering the tyre to the road. NOTEIt should be possible to create an oscillatory movement by lifting and then lowering the back-plate. If this is not possible, t
46、he reason should be investigated or the manufacturer consulted. Static calibration shall conform to Table 1. Table 1 Static calibration Horizontal load applied in line with test wheel axle Recorder output kg 00 to 2 208 to 12 4018 to 22 6029 to 31 8039 to 41 10049 to 51 12059 to 61 14069 to 71 16078
47、 to 82 18088 to 92 20098 to 102 7.2 Dynamic calibration check Carry out a dynamic calibration check, in accordance with annex A, at least once per week during periods of SCRIM operation and after repairs/servicing to the measuring equipment. NOTE 1A dynamic calibration check should also be carried o
48、ut if there is any reason to suspect the validity of the test results. NOTE 2For use on UK trunk roads, SCRIM machines should be checked at least annually in a correlation exercise with other SCRIM machines. 7.3 Distance calibration Carry out a distance calibration, in accordance with annex B, at in
49、tervals not exceeding 3 months, or if the vehicle rear tyres are changed, or if a malfunction is suspected. 8 Test procedure 8.1 Prior to testing Prior to testing check the measurement tyre for pressure and wear. Inspect the water flow system for: position of nozzle; appropriate flow rate on the water control valve; obstruction or damage to the system. 8.2 Testing On the approach to a test length, lower the wheel and allow it to run on the surface, to bring it to stable operating temperature (run for approximately 0.5 km). Running the wheel to stab
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