University of California Pavement Research Center

This report presents a preliminary analysis of slab cracking at the South Tangent sections tested at Palmdale, California using the Heavy Vehicle Simulator (HVS). The data collected on the South Tangent include corner and edge deflections, thermocouple data representing temperature distribution through the slabs, visual and photographic crack surveys, crack activity measurement data, multi-depth deflection data representing deflections at various depths beneath the pavement surface, slab strains measured at critical locations using strain gages, and falling weight deflectometer (FWD) data. The primary focus of this report is the preliminary cracking analysis of the South Tangent slabs. The chief tool used in this analysis is the finite element program, ISLAB2000, which is used to estimate pavement responses for a given geometry under the influence of wheel loadings and layer temperature profiles. The key data used in the analysis include measured corner deflections, thermocouple data, and visual crack survey information along with geometry (slab dimensions) and layer information including FWD backcalculated elastic moduli and modulus of subgrade reaction, coring data, and laboratory measured flexural strength and thermal expansion data. The analysis focuses on the following objectives:

- Estimate an effective linear built-in temperature difference (EBITD) in the slab to simulate the effects of moisture shrinkage and construction temperature gradients.

- Calculate responses including deflections and stresses at critical locations at the top and bottom of the slab. The responses of the slab are significantly affected by moisture shrinkage and construction temperature gradients.

- Evaluate slab cracking by attempting to understand the stress state of the slab.Note that the analyses of other collected data (such as crack activity measurements, multi-depth deflection data, and edge deflection data) are not included in this report. These data will be used in the development of the final comprehensive cracking and joint deterioration model following the analysis of the North Tangent sections.