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Report
2nd European Airport Pavement Workshop, 13 & 14 May 2009
The second European Airport Pavement Workshop focussed on the development of pavement technology and its application to airports held on May 13 and 14, 2009 in the Netherlands. It covered a broad range of pavement technology areas for airports.
Once every 4 years CROW is organising an Airport Pavement Workshop.
The first CROW-European Airport Pavement Workshop in English language was held in May 2005.
Like the first time, the main themes of the workshop are all related to airport pavements:
 pavement design & construction, including PCN calculations and FWD measurements
environmental issues (recycling, sustainability)
safety on pavements (roughness, eveness, bearing capacity)
The themes are indicative and should stimulate the participants to write on similar or related subjects.
Organising Committee
An Organising Committee selects the abstracts and papers in English language to be received.
The Dutch members of the Organising Committee are:
André Molenaar (Delft University of Technology), chairman
Adrian van Leest (CROW Technology Platform), secretary
Janpiet Verbeek (Dutch Ministry of Defence)
Harry van Dijk (Civil Aviation Authority of the Netherlands)
Jan-Paul Apon (Military Aviation Authority of the Netherlands)
Christ van Gurp (KOAC-NPC pavement consultants)
Fer Mooren (NACO airport consultants)
Hilde Bossink (CROW Technology Platform), communications
The international members of the committee are:
Andreas Loizos (National Technical University of Athens, Greece)
Cyril Fabre (AIRBUS S.A.S, France)
Patrick Lerat ( Technical Services Civil Aviation, France)
Airport pavements: increasingly sophisticated models, how realistic are they however?
Advanced models based on finite element theories can easily be used in everyday pavement research, given the fact that computer power is so big nowadays. Advanced data handling resulting in mapping of construction, condition and measurement data is no longer a problem. These are the main conclusions of the second CROW European Airport Pavement Workshop (EAPW), held on Schiphol Airport, last May. During three days, over 100 fellow researchers, consultants and pavement builders from all over the world discussed the latest developments concerning airport pavement. On one of these three days the FAA (Federal Aviation Administration) organised a training course on designing airport pavements, both asphalt and concrete.
The advantage of a workshop over a conference is that there is a two-way interaction between speakers and participants in a workshop, which is highly appreciated.
The knowledge concerning airport pavements developed fast during the last couple of years. The power of the present computers simplifies the application of advanced models based on finite element theories. Besides, advanced data handling resulting in mapping of construction, condition and measurement data is no longer a problem. This results in wonderful models with good surveys of the total pavement. How realistic are they, however? This question was asked several times during the European Airport Pavement Workshop.
True-to-life modeling
Very sophisticated models are available, simplifications are however still applied. At the same time modeling of reality still is a hard thing to do. Moisture migration, joints and load transfers complicate a true-to-life modeling of reality. Correct modeling of material behaviour still is a problem. Fatigue is a specimen property rather than a material property. Right material models must be used in order to be able to analyze the pavement behaviour based on laboratory tests. Which level of sophistication is needed given the very large number of uncertain factors involved and given the large amount of variability in material characteristics and layer thickness? In short: Too many questions.
High contact pressure
High loads and high contact pressures, especially when turning, will result in surface damage and rutting and therefore new materials with enhanced characteristics will be needed. In other words, aircraft manufacturers cannot go on with increasingly less wheels and narrower tires; in the air you cannot use these wheels and it is at the expense of passengers or freight. In case the pressure on the surface caused by the airplane is not divided over a large number of wide tires, the pavement cannot support it. You can compare it with an elephant paw and the stiletto heel. An elephant which weighs 5.000 kilos causes a pressure of 2,5 to 10 kg/cm2, a light-footed lady of 50 kilos on stiletto heels causes 25 to 50 kg/cm2. Although increasing tire pressure from 0,87 to 1,70 MPa at the same tire load, only increases tensile strain at the bottom of the base layer by less than 10%. It does not only concern the runway, but also the route the aircraft has to taxi along the runway. For example: in order to reach the new Polderbaan on Schiphol from the piers, the aircrafts have to cross the A4 highway via a viaduct which has to endure heavy loads.
Completely outdated
The pavement load by aircrafts and the capacity to carry the load is expressed in respectively ACN and PCN, or Aircraft Classification Number and Pavement Classification Number. As long as PCN is higher than ACN, you don’t have a problem, in principle. After all, how accurate can you determine this number? The method for calculating ACN was discussed. The method might be practical, but is completely outdated. Determining the PCN-value takes place by using mechanistic-empirical analysis supported by practical experience.
FWD
The Falling Weight Deflectometer is an excellent tool for scanning purposes. Do we, however, really understand what we are doing? Don’t we expect too much from FWD analyses? Material testing is always needed! It is essential that pavements are smooth and safe but what is smooth and safe? It concerns repeatability and accuracy with regard to carrying out measurements. For this, a relative and absolute calibration is needed. Boeing found out that smoothness problems especially occur in cold regions (Alaska, Canada, Russia) because of frost heave of the pavement. All our advanced models and analyses do not guarantee a good pavement. Further, a high average quality and low variability is required, just like much more attention is needed for construction practises, like training personnel, supervision, quality awareness and use of simple additional tools (temperature sensing, optimising the number of compaction coverages). It’s better to have a well-built however poorly designed construction, than the other way around.
More information
If you wish to receive more information or if you have any questions
Ms. Hilde G. Bossink, communications of the workshop.
mailto: mailto:bossink@crow.nl
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 Programme 2009
At least 40 papers, submitted by 15 countries
More than 40 papers have been submitted by authors from 15 countries, more than enough to create an interesting program about airport pavement technology. The exchange of knowledge and experience is important during the two days.
Submitted abstracts 2009
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