Structural Instrumentation of FAA National Airport Pavement Test Facility
Airport pavement design was historically the result of extrapolating empirical methods of highway engineering origins, some 65 years old. Over 20 years ago, limited full-scale tests were conducted to adapt these methods to accommodate heavier, more complex aircraft. The basic underlying theoretical foundations, although adequate at the time, did not offer a satisfactory method to systematically address the new configurations and high aircraft loads of tomorrow's aircraft; continued use could very well lead to unnecessarily thick pavements. The introduction of the Boeing 777 aircraft in 1995 and the planned introduction of a new generation of heavy civil transport aircraft by manufacturers from both sides of the Atlantic has necessitated a need to develop new pavement design procedures based on sound theoretical principles and with models verified from full-scale test data.
The FAA conceived, designed and constructed a $23,000,000 state-of-the-art, full-scale pavement test facility dedicated solely to airport pavement research. Located at the William J. Hughes Technical Center near Atlantic City, New Jersey, the National Airport Pavement Test Facility (NAPTF) provides high quality, accelerated test data from rigid and flexible pavements subjected to simulated aircraft traffic. Construction of the facility was completed in April 1999. CTLGroup was awarded the contract to design, install and operate the 1000+ sensor primary pavement research instrumentation network, by the design-build contractor, DMJM - Cornell. CTLGroup’s responsibilities included storage and communication hardware/software integration and coordinating with construction of the test pavement.
This ¼-mile-long enclosed test facility is used to provide full-scale response data to study the effects of various wheel load configurations on test pavements. This facility uses nine different heavily instrumented test pavement sections over a 900-foot length to generate input information for new pavement design models.
Nine different types of sensors were installed in the pavement sections, including some developed by CTLGroup, such as asphalt strain gages, concrete strain gages, crack detection gages and the patented Multi-Depth Deflectometer (MDD). All sensors were connected to stand-alone data acquisition systems along track-side, intergrated into a local area network (LAN) controlled by a central computer. The systems are automatically triggered for data collection by test vehicle position.
Sensors have been embedded in the test items to collect data. Sensors are of two types: static and dynamic. Static sensors monitor temperature, moisture and crack status (resistance) on an hourly basis. Dynamic sensors measure quantities such as strain and pavement deflection in response to the load, and are triggered by the vehicle operations. Sensor data collected during traffic test operations will be processed and stored in a computer database maintained on-site. This database will facilitate retrieval of the data for later analysis. Data are then sent over the LAN to the central computer for display, storage and archival.