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Document ID:CIE2006-003
Document Type:Thesis
Author:Melissa Kahl
E-mail Address:
Title:Structural Design of Hollow Extruded WPC Sheet Piling
Department:Civil Engineering
Committee Chair:
Chair's E-mail:
Committee Members:Habib J. Dagher, Ph.D., P.E., Professor of Civil Engineering, Co-Advisor; Roberto Lopez-Anido, Ph.D., P.E., Associate Professor of Civil Engineering, Co-Advisor; Douglas J. Gardner, Ph.D., Professor of Wood Science and Technology; Thomas C. Sandford, Ph.D., P.E., Associate Professor of Civil Engineering
Subjects:Composite materials; Engineered wood; Plastic-impregnated wood
Date of Defense:2006


In marine environments, materials are exposed to a number of harsh environmental factors. Traditional retaining wall materials experience severe degradation as a response to these factors. To address these degradation issues, wood plastic composite (WPC) materials can be used in marine sheet pile applications. WPC materials are both lightweight and durable. This research focuses on developing a sheet pile design that utilizes the material benefits of extruded wood plastic composites with a voided z section sheet pile geometry. The objectives are to develop a more efficient structural design in terms of both material and geometry as compared to the polyvinylchloride (PVC) sheet pile sections currently on the market. To accomplish these objectives, void geometry and placement are selected to maximize profile mechanical properties. Preliminary structural design tables containing the maximum allowable wall height for each section geometry under a variety of backfill conditions and surcharge loadings are then given. For comparison, the hollow WPC section geometric properties are evaluated with respect to the ribbed PVC z sections currently available on the market. A solid finite element model was used to validate the selections made in the preliminary structural design. This model was also used to predict the buckling behavior of the voided z section. The buckling behavior of the z section must be known to properly brace a sheet pile wall during the installation phase. The buckling modes examined were global, local, and distortional. For buckling analysis, traditional analytical expressions were compared with the finite element model. The analytical expressions used for analysis were based on classical plate theory, and the finite element analysis was based on linear eigenvalue buckling. The finite element analysis predicted the buckling modes and critical buckling loads for a single and double voided z-sections. Structural laboratory testing on ribbed PVC double z-sections was also performed to study the flexural behavior of these piles. There are currently no standards for testing a plastic double z-section geometry, and the testing performed brought up many important issues concerned with the test procedure. One of the most important issues is the lateral bracing of the sections, which must provide enough bracing to prevent any twisting of the sections, especially within the joint area. Through preliminary design, finite element analysis, and laboratory testing the process of designing a WPC z-section has begun. These methods have all yielded positive results, indicating the viability of the use of WPC in retaining wall applications.

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Kahl, Melissa, University of Maine, CIE2006-003


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