Nonlinear Temperature Gradient Effects in Dowel Jointed Concrete Slabs

Abstract

The effect of nonlinearity in Temperature Gradient Profile (TGP) on dowel jointed concrete slabs is examined using nonlinear Three-Dimensional Finite Element (3DFE) modeling. The model's thermal response is validated versus field-measured data collected from a heavily instrumented section on the Robert Byrd Highway (Route 33) near Elkins, West Virginia, USA. Results indicate that TGP nonlinearity has its maximum effect on the longitudinal stress 0.28 m away from the transverse joint, i.e. near the end of the embedded dowel bars. A TGP that includes a uniform temperature drop is shown to induce a large magnitude of tensile thermal stress at mid slab. This stress is unaffected by the extent of nonlinearity in TGP and depends on the magnitude of temperature drop and the difference between slab top and bottom temperatures. It is shown that dowel bar bending, due to slab curling, introduces a significant edge restraint to slab contraction and expansion due to ambient temperature changes. Mid-slab longitudinal stress is shown to be minimal for a 4.6 m long slab.

Keywords:

• Thermal stresses
• Finite element
• Dowel bars
• Temperature gradient
• Transverse cracking

Acknowledgements

The work presented in this paper is supported by research grants from the West Virginia Division of Highways (WVDOH). The authors wish to acknowledge the support of the WVDOH staff from Materials Division and District 8 where the instrumented section was constructed. Special thanks are due to Mr Norman Roush, WVDOH who pointed out to the first author the results of thirty years of observations regarding the performance of 15 ft long slabs compared with other concrete slabs of lengths up to 60 ft. Special thanks are due to Mr Fred VanKirk, Secretary of Transportation, who supported this work and was instrumental in bringing the instrumented section of the Robert C. Byrd Highway to reality.