APTech engineers design both HMA and PCC pavements, and can create a suite of alternatives, including various levels of rehabilitation, reconstruction with or without recycling, and completely new designs. Our engineers use conventional design and analysis procedures in addition to other design methodologies and analytical tools to ensure that all design inputs and constraints are thoroughly evaluated to meet the needs of the client.
The most recent APMS update at Vance Air Force Base (AFB) in Enid, Oklahoma identified the need to rehabilitate the pavement on Runway 17R/35L and portions of Taxiways C, F, and G based on their deteriorating surface condition. APTech teamed with Mead & Hunt, Inc. to provide design and construction guidance for the placement of new pavement. As part of this effort, APTech is primarily responsible for evaluating the existing pavement condition and developing recommendation for the new pavement design. To evaluate the pavement, APTech is conducting a visual pavement evaluation, performing FWD testing, and providing input into developing the geotechnical sampling and testing plan. APTech is also developing alternative pavement designs in accordance with UFC 3-260-02, Pavement Design for Airfields, using Pavement-Transportation Computer Assisted Structural Evaluation (PCASE) software, analyzing the alternatives through a life-cycle cost analysis (LCCA), and developing design recommendations. In addition, APTech is providing review and input on the pavement design details, construction plans, and material specifications. Once the pavement design option is selected, APTech will perform additional analyses to determine the Pavement Classification Number (PCN) of the rehabilitated pavements.
In 2014, the Houston Airport System (HAS) was interested in a condition and structural capacity evaluation of a portion of the North Terminal Ramp at Houston George Bush Intercontinental Airport (Texas). The ramp was designed and constructed in 1988 to support loadings of Group IV/V aircraft. HAS was considering expansion of the International Terminal to accommodate the anticipated arrival of Group VI aircraft, in particular the Airbus A380. HAS hired APTech, as a subcontractor to RS&H, Inc., to evaluate a portion of the North Terminal Ramp to ensure that the Group VI aircraft could safely operate on the apron without causing considerable damage.
To perform this assessment, APTech conducted a records review, updated the network definition map, conducted a visual evaluation of pavement that included mapping distresses on every slab, and performed falling weight deflectometer (FWD) testing. APTech analyzed the collected data to determine pavement layer properties, establish structural remaining life, and calculate Pavement Classification Numbers (PCNs) for each pavement section. The results of the pavement assessment indicated that the North Terminal Ramp was in acceptable condition and had the structural capacity required to adequately support the aircraft projected to use them over the next 20 years, including Group VI aircraft. Furthermore, only maintenance and repair activities, and not major rehabilitation or reconstruction, were required to restore the pavement condition. Because APTech mapped distresses on each slab using a GPS-enabled distress data collection tool, APTech was able to pinpoint the exact location of the required maintenance and repair work throughout the ramp.
APTech served as a subcontractor on a project for the Wayne County Airport Authority (WCAA) to provide airfield planning, engineering, and construction management services for the reconstruction of Runway 5R/23L at Willow Run Airport in Ypsilanti, Michigan. Runway 5R/23L is the airport’s longest and only instrumented runway, so its timely rehabilitation is critical to the success of the airport as a whole. APTech’s responsibilities included evaluating the existing pavement structure and developing rehabilitation design alternatives for the rehabilitation of Runway 5R/23L.
Because APTech also performed an APMS update at Willow Run Airport as recently as 2013, information on the history and cross section of the runway was readily available, so APTech was able to immediately begin work on the pavement investigation. APTech’s field efforts included conducting a detailed pavement condition inspection, mapping of critical distresses throughout the runway, performing NDT using a heavy-weight model FWD, and developing a sampling and testing plan of the pavement and subgrade.
The pavement inspections revealed a large amount of cracking, including load-related alligator cracking. The pavement cores confirmed debonding between the hot-mix asphalt (HMA) surface and underlying portland cement concrete (PCC) pavement. Additionally, FWD testing found significant variability in the pavement layer strength and subgrade support conditions, supporting the need for better stabilization and improved drainage. And finally, petrographic examination of the concrete core samples indicated inadequate air content and severe damage due to alkali-silica reactivity (ASR). Collectively, these findings led to a strong recommendation that the runway be reconstructed rather than rehabilitated.
APTech developed alternative pavement designs for both HMA and PCC reconstruction. A herringbone drainage system, consisting of evenly-spaced transverse drains connected to longitudinal underdrains on each side of the runway, was recommended to move water out from under the runway pavement, eliminating the need for a more expensive, stabilized drainage layer.
A life-cycle cost analysis was performed to compare the various alternative pavement designs. The cross section that was ultimately recommended consisted of a 14.5-inch PCC pavement (P-501), 6-inch asphalt-treated base course (P-403), 6-inch crushed stone base (P-209), and 6-inch recycled PCC subbase course (P-219). APTech was also responsible for designing the other pavement details, such as the joint spacing and layout, load transfer, drainage, and paving plan. APTech also developed HMA designs for the pavement transitions and shoulder pavements.
Furthermore, APTech provided review and guidance on the P-501 and other material specifications to ensure the long-term durability of the runway pavement. APTech also provided assistance during the construction phase.
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