Design Inputs

Inputs for Routine Designs

The inputs required to start a routine CalME pavement design are:

•Design life

•Traffic: load distribution (WIM station) and traffic volume in terms of TI (Traffic Index) or indirectly the number of equivalent single axle loads (ESALs)

•Climate zone

•Pavement structure

•Number of layers

•Layer type (e.g., HMA, AB, SG, etc.) and the specific layer material (e.g., 2020 Standard HMA Type A Mix with PG64-16 Binder and up to 15% RAP for non-PRS Projects, 2020 Standard AB-Class 2)

•Layer thickness

•Simulation parameters

•Simulation type: deterministic or Monte Carlo

•Reflection cracking parameters when applicable

•Type of reflection cracking: AC on AC, or AC on cemented base

•For AC on AC, the extent of existing wheelpath cracking

•The cracked layer(s)

•For Monte Carlo simulations:

•Number of simulations, the recommended value is 60

CalME has built-in tools to help select the traffic load distribution (i.e., load spectrum), TI and climate zone once the user enters the project location.

Note: the estimated traffic data provided by CalME is for the lane with maximum traffic, which is typically the outside lane (truck lane). The traffic input data should be replaced by recent traffic data provided by the Caltrans Office of Traffic Operations, if available.

CalME can suggest preliminary simple trial structures for given traffic and climate inputs when designing for new constructions. These guess structures are made up of HMA, AB and SG. Users can also choose to enter different starting structure layers with different thicknesses. The ability for CalME to suggest designs will grow as more pre-run cases are added to the database.

Once all the required inputs are set, the designer can run ME simulations (both Deterministic and Monte Carlo) to see how the design performs with respect to rutting and cracking over the design life of the structure. The deterministic simulation estimates median performance, while the Monte Carlo simulation estimates the distribution of performance and determines the desired quantile (5th percentile by default, corresponding to 95% design reliability). Changes are then made to the initial trial structure and the simulation is run again. This iterative process continues until the desired reliability is obtained that exceeds the minimum 95%.

Inputs for Non-Routine Designs

For non-routine designs such as projects using performance related specification (PRS) for construction, more options are available and can be accessed by granted users. The following is a partial list of the additional options:

•Construction specification type: PRS vs. non-PRS

•Additional materials in the Standard Material Library that

•Represent individual materials from different contractors, districts, and suppliers;

•Account for effects such as geogrid in unbound layer