Researchers at Rowan University – Center for Research and Education in Advanced Transportation Engineering Systems (CREATEs) work on several projects where Heavy Weight Deflectometer (HWD) testing is conducted to evaluate the structural integrity of pavement structures. Using the ELMOD software to analyze large amounts of data, the calculation processes have been simplified and become more efficient.

One of the projects the researchers at CREATEs are working on is the Finite Element Response of Soils at All-Temperature for Cold Regions Pavement Design. In this project, three full-scale pavement test strips were constructed at the Center and are currently being monitored for seasonal variations in temperatures, thermal conductivity, and moisture content in the unbound layers.

Weekly HWD testing at pavement test strips

Periodic HWD testing is conducted weekly on these three strips and will be continued for approximately one year. The output from each HWD test is a set of deflections measured from various geophones spaced across a pavement structure. These deflections are typically used for evaluating the structural integrity of pavement structures as well as back-calculating a pavement structure’s layers moduli.

Comparing estimated and measured deflections

Without a computer program to automate the process, the back-calculation of layers moduli can be tedious and time-consuming. This is the case because to estimate layers moduli, one must first formulate and solve a layered elastic model, using the Layered Elastic Analysis theory or Finite Element Analysis, for the HWD tested pavement structure. In this model seed values of layers, moduli are used as input to calculate estimated deflections within the pavement structures. These deflections are then compared to actual HWD measured deflections and the process is iteratively continued until the error between real and estimated deflections is minimized below an acceptable threshold.

Simplifying back-calculation process with ELMOD software

CREATEs team members are using the ELMOD software to simplify the back-calculation process and efficiently estimate layers moduli of full-scale pavement structures constructed at the Center. ELMOD has made this process easy for the large amount of data they have to analyze.

The ELMOD software has made it easy and more efficient for CREATEs’ researchers to back-calculate layer moduli of full-scale sections tested using the Center’s Heavy Vehicle Simulator (HVS) and Heavy Weight Deflectometer (HWD).

Ayman W. Ali, Ph.D. and Associate Director, CREATEs, Rowan University