Wardle, L. and Rodway, B. (2010). Advanced Design of Flexible Aircraft Pavements. 24th ARRB Conference, Melbourne, Australia.
Road and airfield flexible pavement design methods are similar in that load-induced strains are estimated using layered elastic methods. Pavement life is predicted using materials performance relationships that relate the strains generated within pavement layers and the subgrade to the actual measured performance of full-scale pavements under full-scale loading. The introduction of new generation aircraft such as the Boeing 777 and Airbus A380, both of which have 6-wheel configurations was the major impetus for new full-scale tests to improve the pavement design methods used to determine pavement thicknesses needed for such aircraft. This paper details the recalibration of the computer program, APSDS 5.0 (Aircraft Pavement Structural Design System) to take account of the new test data. To accurately reflect the performance of the test pavements, separate calibrations have been developed for 1, 2, 4 and 6-wheel configurations. Correlation between design outputs and the calibration data is significantly better than achieved by previous calibrations that did not treat the different configurations separately. Structural pavement thicknesses determined by APSDS 5.0 are significantly less than those obtained using the design software FAARFIELD developed in the USA. Possible reasons for the difference are discussed.
Wardle, L. (2010). CIRCLY and Mechanistic Pavement Design: The Past, Present and Towards the Future.
It has been about 30 years since CIRCLY, originally a FORTRAN program for analyzing Layered Elastic Media subject to surface loads, was released by CSIRO. This paper gives an overview of how CIRCLY has evolved over these 30 years – from the first mainframe version, to the current user-friendly Windows based, version 5.0 as the standard pavement design package used in 35 countries. The development of CIRCLY has closely tracked the evolution of the Austroads mechanistic flexible pavement design procedure. CIRCLY is unique amongst commercial software as it handles cross-anisotropic properties as required by the Austroads procedure. CIRCLY also automates many requirements of the Austroads procedure such as sublayering of unbound granular layers. A unique Parametric Analysis feature can fine-tune layer thicknesses to minimize pavement costs. The capabilities of the two special versions of CIRCLY are also discussed:
- APSDS (Airport Pavement Structural Design System) for airport pavements, used for airports world wide such as Frankfurt Airport and Amsterdam’s Schipol Airport. Airbus Industrie has used it to design landing gears for new aircraft models, including the A380.
- HIPAVE (Heavy Industrial PAVEment) for pavements in intermodal container terminals such as the Crawford Street Freight Village in New Zealand.
Some predictions are made about the future of the mechanistic pavement design procedure.
Wardle , L., Rickards, I. and Lancaster, J. (2006). HIPAVE – A Tool To Assist In The Mechanistic Empirical Design Of Heavy Duty Industrial Flexible Pavements. 10th International Conference on Asphalt Pavements (ISAP), Quebec, Canada, August. 12-17.
The HIPAVE (Heavy Industrial PAVEment) layered elastic software program conveniently models the effects of detailed payload distributions (spectrum of container weights) by calculating axle loads from vehicle configurations and payloads, also with provision for vehicle wander. HIPAVE handles the variety of equipment used in container facilities, such as forklifts, straddle carriers, gantry cranes and side loaders. The library of vehicle properties can be automatically updated from the HIPAVE webserver. The HIPAVE package is designed to enable the user to modify any of the design assumptions to reflect empirical observations. The authors caution against the imprudent implementation of design assumptions derived from highway research into industrial pavement designs. Industrial pavements are typically subjected to loading of an order of magnitude greater, making it necessary, for example, to use a different subgrade performance model. As contractors involved in the design and construction of heavy duty industrial flexible pavements the authors observed the absence of a published holistic approach to design that incorporated modern computer software. This fostered the preparation of the Heavy Duty Industrial Pavement Design Guide to assist users of the HIPAVE software, permitting advances in a mechanistic design approach. The Guide presents the authors’ attempts to reflect best practice in the design of new construction and rehabilitation of industrial pavements. The Guide steers the designer through key design considerations and suggests external sources for research updates. It is intended to be supplementary to other published design guides with a focus on industrial pavements. The Guide is a ‘living document’ that will be routinely modified to reflect advances in pavement technology and made freely available via the Internet. It is the authors’ goal to preserve the relevance and currency of the Guide by in-house research and development and continuous liaison with international experts in pavement technology
Wardle, L. J., Rickards, I. and Hudson, K. (2005). HIPAVE – A Mechanistic Design Tool for Heavy-Duty Industrial Pavements. Proc. AAPA Pavements Industry Conf., Surfers Paradise, Australia.
HIPAVE (Heavy Industrial PAVEment design) is for the mechanistic analysis and design of flexible pavements subjected to the extremely heavy wheel loads associated with freight handling vehicles in industrial facilities, in particular, intermodal container terminals. HIPAVE is an outgrowth of CIRCLY and APSDS (Airport Pavement Structural Design System). HIPAVE does a full spectral analysis of pavement damage by using the cumulative damage concept to sum the damage from multiple vehicle models and payloads.
HIPAVE can expedite pavement design projects with these unique features:
- a standard vehicle library – that can be automatically updated via the Internet;
- ability to define and store container weight distributions;
- automatic calculation of axle loads from vehicle geometry and container weight;
- user defined material performance properties (stiffness and transfer functions).
This paper presents the development and advantages of using HIPAVE, over simpler layered elastic tools and empirical chart based methods, to design pavements. HIPAVE has been used for the design of the Crawford Street intermodal container handling facility in Hamilton, New Zealand. This design was complicated by a weak subgrade and height restrictions for the pavement surface. This Crawford Street example demonstrates the efficiencies for designers offered by HIPAVE and the enhanced ability to consider options and conduct ‘what if’ analyses
Wardle, L. J. and Oldfield, D. (2005). HIPAVE – A Mechanistic Design Tool for Flexible Port Pavements. Proc. 2005 Coasts and Ports Australasian Conference, Adelaide, South Australia 21-23 September 2005.
The design of pavements for port facilities is crucial to the successful cargo loading and unloading operations in a safe and efficient environment. Whilst some port pavements are constructed from concrete, the majority of port pavements are of flexible construction with either an asphalt or concrete segmental paver wearing course.
Traditionally, port pavements have been designed using purely chart-based, empirical processes such as the British Ports Association method. In more recent times, designers have combined the full range of vehicles and shipping containers into a single number of repetitions of an ‘equivalent standard axle’. This equivalent axle would be applied in layered elastic design using tools such as CIRCLY.
In 2004, Mincad Systems released a trial version of HIPAVE. This ports-specific version of CIRCLY is designed to allow each combination of vehicle type and container load to be modelled separately and the damage combined using the Cumulative Damage Factor concept.
This paper presents the development and advantages of using HIPAVE, over simpler layered elastic tools and empirical chart based methods, to design flexible port pavements. A design example is also included which presents the design of a port pavement for the Doha Container Terminal in Qatar, using the empirical chart-based method, CIRCLY (via an equivalent axle) and HIPAVE. This example demonstrates the efficiencies for designers offered by HIPAVE and the enhanced ability to conduct ‘what if’ analyses.
Wardle, L. J. and Cropley; S. M. (2004). Integrating Weigh-In-Motion data with Mechanistic Pavement Analysis and Design. in SIIV 2nd International Congress, Florence, Italy, 27-29 October, 2004.
This paper outlines recent work on integrating Weigh-In-Motion (WIM) data into the Australian-developed Mechanistic Pavement Analysis and Design software, HIPAVE (Heavy Industrial Pavement Design System), a special version of CIRCLY with unique features for detailed modelling of traffic load spectra. CIRCLY is an integral component of the Austroads Pavement Design Guide that is widely used in Australia and New Zealand. The prototype system calculates the cumulative damage induced by a traffic spectrum consisting of any combination of user-specified vehicle types and load configurations. The WIM data is imported via an XML (eXtensible Markup Language) format data file that is generated by WIM-Net. The WIM-Net system allows vehicle-by-vehicle data from a variety of WIM devices to be integrated, and allows a user to produce a load spectra consolidated across a group of sites.
Wardle, L.J., Youdale, G. and Rodway, B. (2003). Current Issues For Mechanistic Pavement Design. in 21st ARRB and 11th REAAA Conference, Cairns, Australia, 18 – 23 May, 2003, Session S32, ARRB Transport Research.
This paper discusses four issues currently faced by designers using mechanistic software such as CIRCLY and APSDS to produce pavement designs that are consistent and appropriate. The issues are:
- the choice of appropriate failure criteria
- the treatment of vehicle wander
- negative vertical subgrade strains that can lead to anomalous design results for some pavement geometries
- design of asphalt-surfaced granular pavements,
The first three issues primarily impact the design of heavy duty pavements. The last issue relates to proposed changes to the Austroads (1992) Pavement Design Guide as published in the 2001 Draft Guide (Austroads, 2001).
Wardle, L.J., Rodway, B. and Rickards, I. (2001). Calibration of Advanced Flexible Aircraft Pavement Design Method to S77-1 Method. in Advancing Airfield Pavements, American Society of Civil Engineers, 2001 Airfield Pavement Specialty Conference, Chicago, Illinois, 5-8 August 2001 (Buttlar, W.G. and Naughton, J.E, eds.), pp. 192-201.
This paper outlines the latest APSDS calibration- to the US Army Corps of Engineers CBR method (Method S77-1). The S77-1 design method has been widely used over many years for a wide range of aircraft sizes and subgrade strengths. This experience effectively constitutes an extension to the original empirical test data.
Postscript: The 2001 APSDS Calibration has now been superseded; see Wardle, L. and Rodway, B. (2010).
Advanced Design Of Flexible Aircraft Pavements. Wardle, L. and Rodway, B. (2010). 24th ARRB Conference, Melbourne, Australia.
De Bondt, A.H. (2001). Innovative Airfield Pavement Design.
This paper describes how Ooms Avenhorn Holding used APSDS for the Amsterdam Airport Schiphol 5th runway project.
Rodway, B., Wardle, L.J. and Wickham, G. (1999). Interaction between wheels and wheel groups of new large aircraft. Airport Technology Transfer Conference, Atlantic City, U.S.A., April 1999, Federal Aviation Administration.
This paper shows how current ‘mechanistic’ design methods predict that, for very low strength subgrades, much greater pavement thicknesses will be needed for the B777 and the NLAs. Vertical strain as an indicator of pavement damage often produces anomalous results. Also any design methods that are based simply on the value of a given strain component at a point are unlikely to be fully satisfactory to predict pavement behaviour.
Wardle, L.J. and Rodway, B. (1998). Layered Elastic Pavement Design-Recent Developments. Proceedings Transport 98, 19th ARRB Conference, Sydney, Australia, 7-11 December.
This paper gives an overview of mechanistic pavement design and recent developments in CIRCLY 4.
Rodway, B. and Wardle, L.J. (1998). Layered Elastic Design of Heavy Duty and Industrial Pavements. Proc. AAPA Pavements Industry Conf., Surfers Paradise, Australia.
This paper describes why performance data developed for highway pavements is not appropriate for heavy loadings such as airports and container terminals and can lead to grossly under-designed pavements.
Wardle, L.J. and Rodway, B. (1998). Recent Developments in Flexible Aircraft Pavement Design using the Layered Elastic Method. Third Int. Conf. on Road and Airfield Pavement Technology, Beijing, April 1998.
A good overview, with details of how APSDS differs from LEDFAA.
Wardle, L.J. and Rodway, B. (1995a). An Improved Flexible Airport Pavement Design Method. 20th World Road Congress (Seminar on airfield pavements), Montreal, Canada, 3-9 September,1995.
A brief introduction to APSDS (6 pages)
Wardle, L.J. and Rodway, B. (1995b). Development and Application of an Improved Airport Pavement Design Method. ASCE Transportation Congress, San Diego, 22-26 October, 1995.
A more detailed overview, with details of how we have back-analysed the full scale tests (18 pages).
Rodway, B. (1995a). Design Of Flexible Pavements For Large Multiwheeled Aircraft. Int. Conf. on Road & Pavement Technology, Singapore, 27-29 September, 1995.
A keynote paper that covers the history of airport pavement design and implications for new generation aircraft (31 pages)
Rodway, B. (1995b). The Impact Of New-Generation Large Aircraft on the Structural Design Of Flexible Pavements. Airports 95, Sydney, 9-11 October, 1995.
A summary of the problems in predicting pavement damage due to new generation aircraft (6 pages)