Performance and Assessment of Rehabilitated Steel Culverts

This thesis explores the effects of rehabilitation on the structural performance of corrugated steel culverts. A full-scale laboratory experiment investigated the effects of grouted slip-liners on the performance of two buried circular corrugated steel culverts. One culvert was slip-lined and grouted using low strength grout, while the other was slip-lined and grouted using high strength grout. The performances of the culverts were measured before and after rehabilitation under service loads using single wheel pair loading at 0.45m of cover. Then, the rehabilitated culverts were loaded to their ultimate limit states. Results showed that the low and high strength grouted slip-liners provided strength well beyond requirements, with the low strength specimen failing at a load 2.4 times the fully factored service load, while the high strength specimen did not reach an ultimate limit state before bearing failure of the soil stopped testing. Results also showed that the low strength specimen behaved rigidly under service loads and flexibly under higher loads, while the high strength specimen behaved rigidly under all loads. A second full-scale experiment investigated the effect of a paved invert rehabilitation procedure on the performance of a deteriorated horizontal ellipse culvert. The performance of the culvert before and after rehabilitation was examined under service loads using tandem axle loading at 0.45m of cover. The rehabilitated culvert was then loaded up to its ultimate limit state. The culvert failed due to the formation of a plastic hinge at the West shoulder, while the paved invert cracked at the invert. Results showed that the rehabilitation increased the structural performance of the culvert, increasing the system stiffness and reducing average strains and local bending at critical locations in the culvert under service loads. A sustainability rating tool specifically for the evaluation of deteriorated culvert replacement or rehabilitation projects was also developed. A module for an existing tool, called GoldSET, was created and tested using two case studies, each comparing the replacement of a culvert using a traditional open-cut method with two trenchless rehabilitation techniques. In each case, the analyses showed that the trenchless techniques were the better alternatives in terms of sustainability.

Polymer Process Partitioning: Extruding Plastic Pipe

When plastic pipe is solidified, it proceeds through a long cooling chamber. Inside this chamber, inside the hollow extrudate, the plastic is molten, and this inner surface solidifies last. Sag, the flow due to the self-weight of the molten plastic, then happens in this cooling chamber, and sometimes, thickened regions (called knuckles) arise in the lower quadrants, especially of large diameter thickwalled pipes. To compensate for sag, engineers normally shift the die centerpiece downward. This thesis focuses on the consequences of this decentering. Specifically, when the molten polymer is viscoelastic, as is normally the case, a downward lateral force is exerted on the mandrel. Die eccentricity also affects the downstream axial force on the mandrel. These forces govern how rigidly the mandrel must be attached (normally, on a spider die). We attack this flow problem in eccentric cylindrical coordinates, using the Oldroyd 8-constant constitutive model framework. Specifically, we revise the method of Jones (1964), called polymer process partitioning. We estimate both axial and lateral forces. We develop a corresponding map to help plastics engineers predict the extrudate shape, including extrudate knuckles. From the mass balance over the postdie region, we then predict the shape of the extrudate entering the cooling chamber. We further include expressions for the stresses in the extruded polymer melt. We include detailed dimensional worked examples to show process engineers how to use our results to design pipe dies, and especially to suppress extrudate knuckling.