Performance Assessment and Design Guidelines for RC Three-Sided Culverts
Abstract
Reinforced concrete three-sided culverts (TSCs) are typically produced in large spans, up to 16.0 m, and low-rise profiles to handle heavy flows at sites with limited vertical clearance. Full-scale field studies and numerical analyses investigating TSCs do not exist to date. Accordingly, the current design practices specified in the Canadian Highway Bridge Design Code, CHBDC (CSA, 2014) and the American Association of State and Highway Transportation, AASHTO (AASHTO LRFD, 2014) do not distinguish between small-span box and large-span TSCs. A comprehensive study involving field monitoring and numerical analyses of TSCs is presented in this thesis. Three TSCs were instrumented to measure the soil-culvert interface pressures and the induced strains. The monitored TSCs covered intermediate to large spans, with spans of 7.3 m, 10.4 m, and 13.5 m. Each culvert had a unique geometry and installation method. Field data were collected for the three culverts during and after construction completion. These field measurements were analyzed, and then utilized to verify two-dimensional (2D) finite element (FE) models for the three culverts. The verified numerical models were employed to investigate the influence of many parameters on the applied earth pressures and the structural performance of TSCs at service and ultimate limit states (SLS and ULS). Moreover, three-dimensional (3D) FE models were developed to predict the ultimate capacity of the monitored TSCs precast units. In addition, parametric studies were conducted to investigate the influence of the precast unit width and sidewall height on its structural performance at ULS. The field measurements indicated that the CHBDC (CSA, 2014) overestimates the pressure along the top slab of TSCs for B1 installation. The results of the 2D models showed that the subsurface soil condition influenced the lateral earth pressure on the sidewall only. The sidewall and pedestal heights governed the deformation of the footing-culvert system. Equations have been proposed to estimate the applied earth pressures on large-span TSCs and limits to the midspan vertical deflection are proposed to satisfy the SLS requirements. Finally, the TSC precast units, without soil confinement, exhibited brittle failure.