CRCP design consists of two elements: slab thickness design and steel reinforcement design. The first national CRCP design procedures for slab thickness were developed with information from the AASHO Road Test and were included in the 1972 AASHTO

Interim Guide for Design of Pavement Structures

(AASHTO, 1981). However, the AASHO Road Test only included jointed concrete pavement sections and not CRCP sections. Distresses in jointed concrete pavements (CPCD) are quite different from the distresses observed in modern CRCP. In CRCP, transverse cracking is normal behavior and does not contribute to degradation of serviceability. The behavior of CPCD and CRCP and their effect on pavement performance is quite different from each other, so the use of the AASHO Road Test data for the development of CRCP design procedures is not rational. In some sense, state DOTs reverse-engineered the AASHTO design equations for CRCP design by selecting reasonable values for selected input variables. In 1986 and 1993, extensive revisions were made to the 1972 Interim Guide, and newer versions of the design guides were published. However, very little effort was made to improve the CRCP design portion, except that steel design equations were incorporated.

The department has used the AASHTO 93 Guide for the design of CRCP, and it has served the department well for the design of CRCP, despite its limitations. In March 2004, the report and the mechanistic-empirical pavement design guide software (MEPDG) were released. In 2005, the department initiated to evaluate the MEPDG for potential implementation. The study recommended, for various reasons, not to implement the MEPDG as a replacement for the design methods used at that time.

In 2007, the department initiated a research study, , to develop its own mechanistic-empirical CRCP design procedures that would model the performance of the department’s typical concrete pavement structure and performance. Three-dimensional analysis was conducted for in-depth analysis of mechanistic behavior of CRCP, including the interactions between longitudinal steel and concrete. The project produced a simple Microsoft Excel spreadsheet to perform the design.

The following Figure 8-3 summarizes the CRCP design process.