Load Testing, Analysis, and Design of a New Box Culvert Wing Tab

Abstract

Culverts are critical hydraulic and transportation structures. They are often subjected to complex load conditions such as backfill earth pressure and traffic live load. Culverts may experience total and differential soil settlement of underlying soils, hydrostatic pressure, and aggradation/degradation scour. Any of these may lead to damage, usually in the form of cracking, often immediately after construction. One way to mitigate this problem is to alter the wing wall-to-culvert connection. This research project focused on studying the behavior of a new tabbed wing wall-to-culvert connection design and developing the design guidelines for it. Three culverts with tabbed wing wall-to-culvert connection were constructed in Alabama. During the construction, earth pressure cells were installed on each tab to monitor the changes in the compression pressure that was generated within the tab. This data was used to support the numerical results in predicting the theoretical force normal to the tab surface. The failure mechanism of the wing wall was studied using a non-linear three dimensional finite element analysis. A number of models with different geometries, material properties, design loads, and extreme events were developed. Stage analysis was used to replicate the construction process and model scour development. Distribution of stresses normal to the contraction joint surface and movement of the wing wall were studied. These results were used to predict the maximum forces acting on the tab overlapping surface and state after which the wing wall can no longer perform its function. The design procedure for the new wing wall tab design was developed to articulate with the AASHTO LRFD Bridge Design Specifications (2014). Load and resistance factors were determined using the reliability based procedure involving variability of soil and structure material parameters.