RODOS measures the load-bearing capacity of HWD (Heavy Weight Deflectometer) devices of airport runways and areas. The device allows to perform load tests with a damped impact required load simulating the load of airport roads, aircraft chassis, up to a load of 300 kN resp. contact pressure 4.25 MPa. A wide range of load force settings allows you to measure runway deflections from small sports airports to the largest international airports. The loading force is chosen with regard to the type of road and the road load so that the induced deflections are in the optimal range for further processing.
ACN / PCN load calculations
are performed by U.S. Army software PCASE on the basis of measured values of deflections of the HWD impact device. These tests achieve a realistic evaluation of the condition of individual structural layers. The subsequently determined PCN value expresses the actual load-bearing capacity of the road structure.
PCN values are published in percentiles for each area. This form allows the airport manager to choose a percentile value that:
- ensures the mutual integrity of the bearing capacity of individual areas (i.e. the possibility of aircraft movement starting from the runway, then moving along the TWY to the PRKG and vice versa)
- respects the airport’s marketing plans
- respects maintenance and renovation plans
Practical use of PCN percentile expression for airport administrators:
- for example, a PCN value at the level of the 20th percentile expresses the probability of occurrence of load failures on 20% of the surface of the assessed operating area before the end of the assessment period. Similarly, the 60th percentile represents the probability of failure on 60% of the surface
- The use of the 20th percentile is generally recommended on the new area
Example of a runway with four homogeneous zones (HZ1 – HZ4)
In order to ensure the operation of the planned aircraft, the lowest PCN value was set at 71. This will be achieved at HZ1 with a risk of 45%, at HZ2 with a risk of 80% (accelerated reconstruction must be planned), at HZ3 with a risk of 17% and at HZ4 with a risk of 97% (accelerated reconstruction must be planned).
The PCN is established for the operation of the planned aircraft:
- for a short period (1 to 5 years) in case of poor condition of the areas, when in addition the deflections measured by HWD are high and therefore it is necessary to plan an accelerated reconstruction
- for a long time (10 to 20 years) in the case of new areas and older areas in good condition.