SRT pendulum

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The SRT shuttle (full S kid R esistance T ester ) is a stationary measuring device for detecting the grip of the road surface and markings. It measures the micro-roughness and is used together with the Moore discharge meter, which measures the macro-roughness. It was developed in Great Britain in order to be able to carry out measurements with little effort, but is no longer used there due to inaccuracy.

Measuring device

The basic principle of the SRT pendulum consists of a three-armed base frame equipped with foot screws and a circular level, which carries a column to hold a scale plate and a bearing head together with a pendulum arm and drag pointer. The stability of the measuring device must be guaranteed.

At the end of the pendulum arm, the so-called sliding shoe is attached, which carries a sliding body that can move in two axes. The sliding body consists of a rubber with a fixed degree of hardness. When the pendulum arm is triggered, this sliding body glides with a constant contact pressure of 22.2 Newtons and a speed of 10 km / h over the surface to be tested and wetted with water. The frictional resistance (resulting energy loss) is determined and displayed on the scale plate using the drag pointer.

The value determined here is the SRT value . The higher the breakdown of the actual pendulum, the lower the value of the SRT unit and, consequently, the existing grip of the test document. Road markings, for example, must achieve an average grip of at least 45 SRT units. The measurement result results from the mean value from five measurements. These are carried out along a line at a distance of 5 meters. The pendulum test is carried out five times at each of these measuring points.

standardization

The SRT pendulum is currently the only device harmonized by CEN for measuring grip. In Germany it is currently approved for control measurements in road construction and has to be calibrated annually by a calibration center approved by the BASt . The CEN implementation standard is still pending, but the CEN / TS 15676 pre-standard exists for use on wooden floors.

literature

  • S. Velske, H. Mentlein: Road construction technology . Werner Verlag, Düsseldorf 2002, ISBN 3-8041-3875-6 , p. 262 .