Introduction To CalME v3.1

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Historical Background on Mechanistic-Impirical Design in California

In 2005, the California Department of Transportation (Caltrans) approved an issue memo titled “Adoption of Mechanistic-Empirical (ME) Pavement Design Method,” which calls for the adoption of ME pavement design methodology to replace existing pavement design methods that have been in place since the early 1960s.

The University of California Pavement Research Center (UCPRC) has been supporting the Caltrans effort to implement ME pavement design by working on a series of tasks since 2000. This work is under the technical guidance of the Pavement Standards Team, with the Division of Design in the lead. One of those tasks is to develop and calibrate ME flexible pavement design models.

The first step in creating a Mechanistic-Empirical (ME) pavement design or evaluation is to calculate pavement response - in terms of stresses, strains, and/or displacements - using a mathematical (or mechanistic) model. In the second step, the calculated response is used as a variable in empirical relationships to predict structural damage (decrease in moduli or cracking) and functional damage (rutting and roughness) to the pavement.

Both of these steps must be reasonably correct. If the calculated response bears little resemblance to the pavement’s actual response, there is no point in trying to use the calculation to predict future damage to the pavement with the empirical relationship. In other words, only if the calculated response is reasonably correct does it make sense to try to relate the damage to the pavement response.

The validation and calibration of the models in CalME was first performed using performance data from Heavy Vehicle Simulator (HVS) tests completed by the UCPRC between 1995 and 2004. The results of that work are documented in a separate report titled “Calibration of Incremental-Recursive Flexible Damage Models in CalME Using HVS Experiments".

CalME Versions 1 and 2

The first version of CalME, v1, was released in 2011, and the second version, v2, was released in 2014; these were both desktop applications written Visual Basic. The desktop application was originally developed as a research tool that had a working user interface and workflow but it was very hard to maintain and enhance. The installation of the desktop application proved to be cumbersome to Caltrans since administrative privileges were required.

CalME Version 3!

CalME v3 is a complete rewrite of the desktop version of CalME (v2). CalME v3 is now a web-based application (using Microsoft's ASP.NET technology) that accesses the services of new, modern and easy-to-maintain ME compute engine written in C++ which is optimized for performance. CalME v3 has been tested against v2 and the results are the same.

CalME v3 uses the same traffic data used by Caltrans' pavement management system, PaveM. This source of traffic is more current than that used by v2 and it also uses traffic information from the PeMS system in order to fine-tune traffic. As a result, traffic is now a segment-based system, rather than a point-based system used by v2. Consequently, traffic data is automatically determined by CalME based on the location of the project on the highway system. This means that users no longer need to make a selection for the location of traffic count data, as was the case in v2. CalME v3 makes a suggestion on the most appropriate truck load distribution (WIM station) to use. The user may select a different WIM if desired.

CalME v3 also uses the same Climate Zone data used by PaveM and also makes a suggestion for the best zone to use. Again, the user is able to select any zone.

CalME v3 has incorporates Caltrans' CalFP (new pavement design) and CalAC (rehab design) design procedures. The desktop versions of these applications will eventually be retired so CalME v3 will soon be the only way to run these applications, in addition to performing ME simulations.

CalME v3 also allows the import of Caltrans' CalBack data via a export file. CalME v3 create a new project and a series of trials that represents the sections generated by CalBack.