Numerical Analysis of the Potential for Joint Separation in Round Concrete Culverts

Abstract

A common form of damage experienced by culverts is joint separation between culvert segments. Joint performance issues may allow water and soil to seep through the pipe leading to loss of soil support, which may ultimately result in roadway settlement or failure of the pipe. The factors that contribute to joint separation are unclear, and although past studies have investigated flexural demands across joints, no current studies are examining the axial tension demands that may develop across culvert joints. To this end, finite difference and finite element models of round concrete culverts were developed to examine the potential for separation from axial demands on culvert segments. The models investigated traffic loading, rise of the phreatic surface, freezing of the embankment, and dead load demands under the self-weight of the embankment. All of the above mechanisms led to axial tension along the length of the pipe. Of these, traffic loading caused the lowest separation forces, roughly 10% to 20% of the applied vertical load occurring under the roadway. Embankment self-weight caused built-in tensile demands under the driving surface. The rise of the phreatic surface and freezing of the embankment also caused significant separation forces, but near the embankment face. For untied pipe segments, increased depth to the culvert centerline and reduced embankment stiffness were the most critical parameters that increased the potential for joint separation. Further research focusing on detailed field observations to confirm the most likely locations of and conditions that lead to joint separation in culverts is recommended.