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Evaluating Runway Designs - Part 2
"Making Corrections on Paper - Not Pavement" Mike Freeman - October 20, 2011 The last article addressed the importance of evaluating designs from a pavement roughness perspective. An example was given of an airport that did not evaluate a design and ended up with a closed runway and lots of finger pointing. At a different major airport in the Eastern US, a more proactive approach was taken. Pavement owners and engineers were preparing to replace a long asphalt runway with concrete. In order to do this, the plan was to raise the elevation of the entire runway by approximately 18 inches. Because of this elevation change, concerns were raised about how the changes would affect the intersecting runway. Aircraft operating on the intersecting runway would feel a “bump” as they went up and over the new, 18-inch high concrete runway. APR was contacted to evaluate the intersection design in order to determine how much unwanted aircraft response would be generated. After thoroughly examining the intersection design from a roughness point of view, it was concluded that the bump created by raising the runway 18 inches was too large and would generate significant unwanted aircraft response for aircraft operating on the intersecting runway. It was recommended that the elevation change of the new runway be taken down to 12 inches instead of 18. In addition, it was recommended that an additional vertical curve be added on both sides of the intersection to soften the grade changes. Simulations showed that these changes significantly lessened aircraft response. The pavement owners and engineers took the recommendations and incorporated them into the design while maintaining their non-smoothness related concerns. They produced a new design and submitted the changes to APR. After thoroughly examining the new intersection design, it was determined that it was not only acceptable, but better than the existing intersection. Once they had our approval, the engineers were able to get buy-in on the project from the pilot’s association and other stakeholders. From the beginning of the project, the intersection was a major concern and having the approval of a third party gave everyone involved peace of mind. Engineers were able to use our simulation plots to give assurance that the intersection would not cause unwanted aircraft response, even with the elevation changes being made. Finally, after the runway was built we were called to evaluate the final product. Once we measured the “as-is” elevation data, we compared the data to the design and performed our complete analysis. The runway intersection was built to the design and passed every part of our analysis. By remaining pro-active toward pavement roughness throughout this entire project, the airport was able to save valuable time and resources by correcting problems on paper and not in the field. If we can help you with a new pavement design, please contact us. |
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