Civil Engineering ETDs

Publication Date



Falling Weight Deflectometer (FWD) test data are processed by backcalculation software to obtain modulus of layer materials of airport pavements. Currently, several backcalculation software are available. However it is not known which software produces accurate and consistence modulus values. In this study three backcalculation software; namely, BAKFAA, EVERCALC, and MODULUS are evaluated for consistency and accuracy. To examine accuracy, software predicted modulus values are compared to the laboratory tested modulus values of soils, aggregate, and asphalts. Consistency is examined by statistical analysis using three sets of FWD deflection data produced by three loads with magnitudes of 9, 12, and 16 kip at an identical location of an airport pavement. It is shown that EVERCALC software produces more consistent and accurate modulus values than the BAKFAA and MODULUS software. A concern with the available backcalculation software is that their analysis algorithms are based on layered elastic theory with linear materials models. In addition, they consider static loading, which is not the true representation of the dynamic loads applied in a FWD test in the field. To this end, this study performs a dynamic analysis of the FWD deflection basin using a finite element method (FEM) with the consideration of non-linear materials models. Results show that FEM predicted deflections have similar trends of the field measured deflections. However, a number of trial combinations of inputs and FEM models may be required to produce an identical match between the predicted and measured deflections. It is recommended that this approach be the subject of future studies.


Runways (Aeronautics)--Testing--Data processing, Pavements--Testing--Data processing, Nondestructive testing--Data processing, Structural analysis (Engineering)--Statistical methods, Finite element method.

Document Type




Degree Name

Civil Engineering

Level of Degree


Department Name

Civil Engineering

First Advisor

Tarefder, Rafiqul

First Committee Member (Chair)

Ng, Tang -Tat

Second Committee Member

Stormont, John