A Mechanistic-Empirical Tie Bar Design Procedure
This paper presents a mechanistic-empirical (M-E) method of tie bar design for portland cement concrete (PCC) pavements. Current tie bar design practice is based on subgrade drag theory (SDT)—a simplified limit state theory. The M-E method considers the real static state of the system of PCC slabs-base-tie bars under environmental loading (temperature drop and drying shrinkage). Concrete slabs are modeled as elastic plates capable of horizontal movement. A bilinear spring model is used for modeling friction at the slab-base interface, and a linear model is used for modeling tie bar shear and pullout. This paper describes the development of the M-E design method and includes the results of a sensitivity analysis for basic design parameters. A comparison with the SDT-based method demonstrates that the M-E method produces similar calculated tie bar spacing for unbound materials but significantly different results for cement stabilized bases. Level of calculated slab tensile stresses due to environmental loading is very low in the case of unbound bases and reaches significant values for very stiff stabilized bases.
TRT Terms: Concrete pavements; Design; Pavement design; Portland cement concrete; Shear strength; Shrinkage; Slabs; Subgrade (Pavements); Tie bars