Analysis of Falling Weight Deflectometer Tests at Denver International Airport

Computer Applications to Airport Pavements

Data collected from heavy weight deflectometers (HWD) tests at the Federal Aviation Administration (FAA) instrumented Portland cement concrete (PCC) pavement test site at Denver International Airport (DIA) are used to analyze the deflection response of the pavement. The HWD tests are conducted routinely for slabs in both the traffic and the nontraffic area. The deflection measurements show that a linear relationship exists between surface deflection and load at the center of the slabs and at the mid-points of the joints. Some of the tests were also run with the HWD weight dropped directly over multidepth deflectometers (MDDs) in the pavement. Deflections at the interior, joints, and corners of a slab measured by the HWD are compared to those measured by the MDDs at different depths. The analysis shows that the movement of an anchor at 3 meter (10 feet) below the slab surface had significant effects on the measured pavement surface deflection while the effects of movement of an anchor at 6-meter (20-feet) depth may be negligible. The analysis also indicates that a gap existed between the bottom of the PCC slab and the top of the econocrete base layer at the slab corners and at the joints. A load transfer analysis, including measurements of the strain response of the PCC slab under HWD loading, indicates that the load transfer capability of hinged joints was very stable for all the seasons, but that the load transfer capability of dummy joints varied significantly in a year. The load transfer capability of the dummy joints became very small during the winter but returned to normal (equal to even higher than is expected by the FAA design specification) in the summer.

Authors: May Dong, Gordon F. Hayhoe